Guidelines for Effective Residential Solar Shading ...

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Guidelines for Effective Residential Solar Shading Devices

IRC-RR-300 Laouadi, A.

March 2010 :

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2010 GUIDELINES FOR EFFECTIVE RESIDENTIAL SOLAR SHADING DEVICES

A. Laouadi Indoor Environment Research Program Institute for Research in Construction National Research Council Canada 1200 Montreal Road, Ottawa, Ontario, K1A 0R6, Canada

National Research Council of Canada 3/5/2010 1

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TABLE OF CONTENTS LIST OF RELATED PUBLICATIONS .................................................................................................................. 11  JOURNAL AND CONFERENCE PAPERS ........................................................................................................................ 11  TRADE MAGAZINES .................................................................................................................................................. 11  EXECUTIVE SUMMARY ....................................................................................................................................... 12  SOMMAIRE .............................................................................................................................................................. 15  INTRODUCTION ..................................................................................................................................................... 19  OBJECTIVES ............................................................................................................................................................ 20  PERFORMANCE METRICS OF WINDOW AND SHADING SYSTEMS ........................................................ 20  LIGHT DIFFUSION INDEX (HAZE) .............................................................................................................................. 20  VISIBLE TRANSMITTANCE (TVIS) ............................................................................................................................ 21  ULTRA-VIOLET TRANSMITTANCE (TUV) ................................................................................................................. 21  FADING TRANSMITTANCE (TFD).............................................................................................................................. 21  SKIN DAMAGE TRANSMITTANCE (TSD) ................................................................................................................... 21  SOLAR HEAT GAIN COEFFICIENT (SHGC) ............................................................................................................... 21  THERMAL TRANSMITTANCE OF GLAZING ASSEMBLY (U-FACTOR) .......................................................................... 21  THERMAL TRANSMITTANCE OF EDGE-OF-GLAZING (U- FACTOR -EDGE) ................................................................. 22  LUMINANCE INDEX (LI)............................................................................................................................................ 22  VIEW-OUT INDEX (VOI) .......................................................................................................................................... 22  MOISTURE CONDENSATION INDICATOR ................................................................................................................... 22  PERFORMANCE DATA OF WINDOW AND SHADING SYSTEMS ............................................................... 23  UN-SHADED WINDOWS ............................................................................................................................................ 24  WINDOWS WITH TYPICAL INTERIOR BLINDS ............................................................................................................. 26  WINDOWS WITH INTERIOR REFLECTIVE BLINDS ........................................................................................................ 29  WINDOWS WITH INTERIOR REFLECTIVE SCREEN SHADINGS ...................................................................................... 30  WINDOWS WITH BETWEEN-PANE REFLECTIVE BLINDS .............................................................................................. 33  WINDOWS WITH EXTERIOR ROLLSHUTTERS .............................................................................................................. 36  WINDOWS WITH EXTERIOR SCREEN SHADINGS ......................................................................................................... 38  ANNUAL HEATING AND COOLING ENERGY USE AND COST .................................................................. 41  UN-SHADED WINDOWS ............................................................................................................................................. 42  Results for Ottawa ............................................................................................................................................... 42  Results for Montreal ............................................................................................................................................ 44  Results for Winnipeg ............................................................................................................................................ 45  Results for Halifax ............................................................................................................................................... 47  WINDOWS WITH TYPICAL INTERIOR BLINDS ............................................................................................................. 49  Results for Ottawa ............................................................................................................................................... 49  Results for Montreal ............................................................................................................................................ 51  Results for Winnipeg ............................................................................................................................................ 52  Results for Halifax ............................................................................................................................................... 54  3

WINDOWS WITH INTERIOR REFLECTIVE BLINDS ........................................................................................................ 55  Results for Ottawa ............................................................................................................................................... 55  Results for Montreal ............................................................................................................................................ 57  Results for Winnipeg ............................................................................................................................................ 58  Results for Halifax ............................................................................................................................................... 60  WINDOWS WITH INTERIOR REFLECTIVE SCREENS ..................................................................................................... 61  Results for Ottawa ............................................................................................................................................... 61  Results for Montreal ............................................................................................................................................ 63  Results for Winnipeg ............................................................................................................................................ 64  Results for Halifax ............................................................................................................................................... 66  WINDOWS WITH BETWEEN-PANE REFLECTIVE BLINDS .............................................................................................. 67  Results for Ottawa ............................................................................................................................................... 67  Results for Montreal ............................................................................................................................................ 69  Results for Winnipeg ............................................................................................................................................ 70  Results for Halifax ............................................................................................................................................... 72  WINDOWS WITH EXTERIOR ROLLSHUTTERS .............................................................................................................. 73  Results for Ottawa ............................................................................................................................................... 73  Results for Montreal ............................................................................................................................................ 75  Results for Winnipeg ............................................................................................................................................ 77  Results for Halifax ............................................................................................................................................... 78  WINDOWS WITH EXTERIOR SCREENS ........................................................................................................................ 80  Results for Ottawa ............................................................................................................................................... 80  Results for Montreal ............................................................................................................................................ 81  Results for Winnipeg ............................................................................................................................................ 83  Results for Halifax ............................................................................................................................................... 84  PEAK COOLING POWER DEMAND ................................................................................................................... 86  ON-PEAK COOLING POWER DEMAND ...................................................................................................................... 86  AIR-CONDITIONER PEAK POWER .............................................................................................................................. 88  Results For Ottawa .............................................................................................................................................. 88  Results For Montreal ........................................................................................................................................... 89  Results For Winnipeg .......................................................................................................................................... 90  Results For Halifax .............................................................................................................................................. 91  PAYBACK RETURN PERIODS ............................................................................................................................. 92  CONCLUSIONS ........................................................................................................................................................ 94  REFERENCES .......................................................................................................................................................... 99  ACKNOWLEDGMENT ......................................................................................................................................... 101  APPENDIX A: METHODOLOGY FOR BUILDING-ENERGY COMPUTER SIMULATION.................... 102  ESP-R COMPUTER PROGRAM .................................................................................................................................. 102  SKYVISION COMPUTER PROGRAM .......................................................................................................................... 102  HOUSE GEOMETRY MODEL .................................................................................................................................... 102  HOUSE CONSTRUCTION .......................................................................................................................................... 103  WINDOW TYPES ..................................................................................................................................................... 106  SHADING DEVICE TYPES ........................................................................................................................................ 108  4

OPERATIONAL SCHEDULE OF SHADING DEVICES ................................................................................................... 108  HOUSE INTERIOR HEAT GAINS ............................................................................................................................... 110  HEATING AND COOLING EQUIPMENT ..................................................................................................................... 111  CLIMATES AND REGIONS ........................................................................................................................................ 112  EXPERIMENTAL VALIDATION OF THE SIMULATION MODEL..................................................................................... 112  APPENDIX B: LIST OF SHADING MANUFACTURERS ................................................................................ 115 

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LIST OF FIGURES Figure 1

Moisture condensation on the interior surfaces of un-shaded windows at an indoor temperature of 21oC. ................................................................................................................. 26 

Figure 2

Moisture condensation on the interior surfaces of windows with interior typical blinds in an open position when the indoor temperature is set at 21oC. ...................................................... 28 

Figure 3

Moisture condensation on the interior surfaces of windows with interior typical blinds in a closed position when the indoor temperature is set at 21oC. .................................................... 29 

Figure 4

View-out through a double clear low-e window (DLCE) with an interior reflective roller screen shade......................................................................................................................................... 31 

Figure 5 Condensation on the interior surfaces of windows with interior screen shadings. ....................... 33  Figure 6

Moisture condensation on the interior surfaces of windows with between-pane metallic blinds in an open position when the indoor temperature is set at 21oC. ............................................. 35 

Figure 7

Moisture condensation on the interior surfaces of windows with between-pane metallic blinds in a closed position when the indoor temperature is set at 21oC. ............................................. 36 

Figure 8 Exterior rollshutter in a closed position. ........................................................................................ 37  Figure 9

Moisture condensation on the interior surfaces of windows with exterior rollshutters when the indoor temperature is set at 21oC. ............................................................................................ 38 

Figure 10 Exterior screen shadings in a closed position. ........................................................................... 40  Figure 11 Moisture condensation on the interior surfaces of windows with exterior screen shadings when the indoor temperature is set at 21oC. ...................................................................................... 40  Figure 12 Annual heating and cooling energy use of old and R-2000 house models with un-shaded windows (Ottawa, ON). ............................................................................................................. 43  Figure 13 Annual total and heating energy cost of old and R-2000 house models with un-shaded windows (Ottawa, ON). ............................................................................................................. 43  Figure 14 Annual heating and cooling energy use of old and R-2000 house models with un-shaded windows (Montreal, QC)............................................................................................................ 44  Figure 15 Annual total and heating energy cost of old and R-2000 house models with un-shaded windows (Montreal, QC)............................................................................................................ 45  Figure 16 Annual heating and cooling energy use of old and R-2000 house models with un-shaded windows (Winnipeg, MB)........................................................................................................... 46  Figure 17 Annual total and heating energy cost of old and R-2000 house models with un-shaded windows (Winnipeg, MB)........................................................................................................... 47  Figure 18 Annual heating and cooling energy use of old and R-2000 house models with un-shaded windows (Halifax, NS). .............................................................................................................. 48  Figure 19 Annual total and heating energy cost of old and R-2000 house models with un-shaded windows (Halifax, NS). .............................................................................................................. 49 

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Figure 20 Annual heating and cooling energy use of old and R-2000 house models with typical interior window blinds (Ottawa, ON)...................................................................................................... 50  Figure 21 Annual total and heating energy cost of old and R-2000 house models with typical interior window blinds (Ottawa, ON)...................................................................................................... 50  Figure 22 Annual heating and cooling energy use of old and R-2000 house models with typical interior window blinds (Montreal, QC). .................................................................................................. 51  Figure 23 Annual total and heating energy cost of old and R-2000 house models with typical interior window blinds (Montreal, QC). .................................................................................................. 52  Figure 24 Annual heating and cooling energy use of old and R-2000 house models with typical interior window blinds (Winnipeg, MB). ................................................................................................. 53  Figure 25 Annual total and heating energy cost of old and R-2000 house models with typical interior window blinds (Winnipeg, MB). ................................................................................................. 53  Figure 26 Annual heating and cooling energy use of old and R-2000 house models with typical interior window blinds (Halifax, NS). ..................................................................................................... 54  Figure 27 Annual total and heating energy cost of old and R-2000 house models with typical interior window blinds (Halifax, NS). ..................................................................................................... 55  Figure 28 Annual heating and cooling energy use of old and R-2000 house models with interior reflective window blinds (Ottawa, ON)...................................................................................................... 56  Figure 29 Annual total and heating energy cost of old and R-2000 house models with interior reflective window blinds (Ottawa, ON)...................................................................................................... 56  Figure 30 Annual heating and cooling energy use of old and R-2000 house models with interior reflective window blinds (Montreal, QC). .................................................................................................. 57  Figure 31 Annual total and heating energy cost of old and R-2000 house models with interior reflective window blinds (Montreal, QC). .................................................................................................. 58  Figure 32 Annual heating and cooling energy use of old and R-2000 house models with interior reflective window blinds (Winnipeg, MB). ................................................................................................. 59  Figure 33 Annual total and heating energy cost of old and R-2000 house models with interior reflective window blinds (Winnipeg, MB). ................................................................................................. 59  Figure 34 Annual heating and cooling energy use of old and R-2000 house models with interior reflective window blinds (Halifax, NS). ..................................................................................................... 60  Figure 35 Annual total and heating energy cost of old and R-2000 house models with interior reflective window blinds (Halifax, NS). ..................................................................................................... 61  Figure 36 Annual heating and cooling energy use of old and R-2000 house models with interior reflective window screens (Ottawa, ON). ................................................................................................. 62  Figure 37 Annual total and heating energy cost of old and R-2000 house models with interior reflective window screens (Ottawa, ON). ................................................................................................. 62  Figure 38 Annual heating and cooling energy use of old and R-2000 house models with interior reflective window screens (Montreal, QC). ............................................................................................... 63 

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Figure 39 Annual total and heating energy cost of old and R-2000 house models with interior reflective window screens (Montreal, QC). ............................................................................................... 64  Figure 40 Annual heating and cooling energy use of old and R-2000 house models with interior reflective window screens (Winnipeg, MB). .............................................................................................. 65  Figure 41 Annual total and heating energy cost of old and R-2000 house models with interior reflective window screens (Winnipeg, MB). .............................................................................................. 65  Figure 42 Annual heating and cooling energy use of old and R-2000 house models with interior reflective window screens (Halifax, NS). .................................................................................................. 66  Figure 43 Annual total and heating energy cost of old and R-2000 house models with interior reflective window screens (Halifax, NS). .................................................................................................. 67  Figure 44 Annual heating and cooling energy use of old and R-2000 house models with between-pane reflective window blinds (Ottawa, ON). ..................................................................................... 68  Figure 45 Annual total and heating energy cost of old and R-2000 house models with between-pane reflective window blinds (Ottawa, ON). ..................................................................................... 68  Figure 46 Annual heating and cooling energy use of old and R-2000 house models with between-pane reflective window blinds (Montreal, QC). .................................................................................. 69  Figure 47 Annual total and heating energy cost of old and R-2000 house models with between-pane reflective window blinds (Montreal, QC). .................................................................................. 70  Figure 48 Annual heating and cooling energy use of old and R-2000 house models with between-pane reflective window blinds (Winnipeg, MB). ................................................................................. 71  Figure 49 Annual total and heating energy cost of old and R-2000 house models with between-pane reflective window blinds (Winnipeg, MB). ................................................................................. 71  Figure 50 Annual heating and cooling energy use of old and R-2000 house models with between-pane reflective window blinds (Halifax, NS). ...................................................................................... 72  Figure 51 Annual total and heating energy cost of old and R-2000 house models with between-pane reflective window blinds (Halifax, NS). ...................................................................................... 73  Figure 52 Annual heating and cooling energy use of old and R-2000 house models with exterior window rollshutters (Ottawa, ON). ......................................................................................................... 74  Figure 53 Annual total and heating energy cost of old and R-2000 house models with exterior window rollshutters (Ottawa, ON). ......................................................................................................... 75  Figure 54 Annual heating and cooling energy use of old and R-2000 house models with exterior window rollshutters (Montreal, QC). ....................................................................................................... 76  Figure 55 Annual total and heating energy cost of old and R-2000 house models with exterior window rollshutters (Montreal, QC). ....................................................................................................... 76  Figure 56 Annual heating and cooling energy use of old and R-2000 house models with exterior window rollshutters (Winnipeg, MB). ...................................................................................................... 77  Figure 57 Annual total and heating energy cost of old and R-2000 house models with exterior window rollshutters (Winnipeg, MB). ...................................................................................................... 78 

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Figure 58 Annual heating and cooling energy use of old and R-2000 house models with exterior window rollshutters (Halifax, NS). .......................................................................................................... 79  Figure 59 Annual total and heating energy cost of old and R-2000 house models with exterior window rollshutters (Halifax, NS). .......................................................................................................... 79  Figure 60 Annual heating and cooling energy use of old and R-2000 house models with exterior window screens (Ottawa, ON). .............................................................................................................. 80  Figure 61 Annual total and heating energy cost of old and R-2000 house models with exterior window screens (Ottawa, ON). .............................................................................................................. 81  Figure 62 Annual heating and cooling energy use of old and R-2000 house models with exterior window screens (Montreal, QC). ............................................................................................................ 82  Figure 63 Annual total and heating energy cost of old and R-2000 house models with exterior window screens (Montreal, QC). ............................................................................................................ 82  Figure 64 Annual heating and cooling energy use of old and R-2000 house models with exterior window screens (Winnipeg, MB). ........................................................................................................... 83  Figure 65 Annual total and heating energy cost of old and R-2000 house models with exterior window screens (Winnipeg, MB). ........................................................................................................... 84  Figure 66 Annual heating and cooling energy use of old and R-2000 house models with exterior window screens (Halifax, NS). ............................................................................................................... 85  Figure 67 Annual total and heating energy cost of old and R-2000 house models with exterior window screens (Halifax, NS). ............................................................................................................... 85  Figure 68 Peak cooling power demand during two sunny and hot summer days for old houses with conventional double clear windows in Ottawa (based on a 15-minute time step). ................... 87  Figure 69 Peak cooling power demand during two sunny and hot summer days for R-2000 houses with double clear low-e windows in Ottawa (based on a 15-minute time step). ............................... 88  Figure 70 Effect of the shading devices on the peak power demand of an air-conditioner for an old versus an R-2000 house model (Ottawa, ON). ......................................................................... 89  Figure 71 Effect of the shading devices on the peak power demand of an air-conditioner for an old versus an R-2000 house model (Montreal, QC). ...................................................................... 90  Figure 72 Effect of the shading devices on the peak power demand of an air-conditioner for an old and versus an R-2000 house model (Winnipeg, MB). ..................................................................... 91  Figure 73 Effect of the shading devices on the peak power demand of an air-conditioner for an old versus an R-2000 house model (Halifax, NS)........................................................................... 92  Figure 74 The CCHT house geometry model as simulated. Note that the window frames were treated as separate surfaces. The house is oriented north-south. ...................................................... 103  Figure 75 Hourly averaged measured and simulated heating energy demands of the CCHT house with interior blinds in an open position (slats horizontal day and night). ........................................ 114  Figure 76 Hourly averaged measured and simulated ground floor temperatures of the CCHT house with interior blinds in an open position during a cold, sunny winter day......................................... 114 

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LIST OF TABLES Table 1

Performance metrics of un-shaded windows (for the combined centre and edge of glass sections). ................................................................................................................................... 25 

Table 2

Performance metrics of windows with interior typical blinds (for the combined centre and edge of glass sections). ..................................................................................................................... 27 

Table 3

Performance metrics of windows with interior reflective metallic blinds (for the combined centre and edge of glass sections). ..................................................................................................... 30 

Table 4

Performance metrics of windows with interior reflective screen shadings (for the combined centre and edge of glass sections). .......................................................................................... 32 

Table 5

Performance metrics of windows with between-pane reflective metallic blinds (for the combined centre and edge of glass sections)........................................................................... 34 

Table 6 Performance metrics of windows with exterior rollshutters (for the combined centre and edge of glass sections)........................................................................................................................... 37  Table 7

Performance metrics of windows with exterior screen shadings (for the combined centre and edge of glass sections). ............................................................................................................ 39 

Table 8

Types and cost of fuels used for house heating and cooling. Data for heating fuel were taken from StatsCan (2008) and data for electricity cost were taken from Hydro Quebec (2008). .... 41 

Table 9 Cost of shading devices to fit the house windows. ........................................................................ 93  Table 10

Simple payback return periods (in years) of the studied shading devices for old houses with double clear windows, and R-2000 houses with double clear low-e windows. ........................ 94 

Table 11 Annual total energy cost savings of shading devices for old houses with conventional double clear windows and R-2000 houses with double clear low-e windows in Ottawa, Ontario. ....... 97  Table 12 Annual total energy cost savings of shading devices for old houses with conventional double clear windows and R-2000 houses with double clear low-e windows in Montreal, Quebec. .... 97  Table 13

Annual total energy cost savings of shading devices for old houses with conventional double clear windows and R-2000 houses with double clear low-e windows in Winnipeg, Manitoba. 98 

Table 14

Annual total energy cost savings of shading devices for old houses with conventional double clear windows and R-2000 houses with double clear low-e windows in Halifax, Nova Scotia. 98 

Table 15 Construction material details of current houses built according to the R-2000 standard. ......... 104  Table 16 Construction material details for old houses built in 1980 in Ottawa, Ontario. .......................... 105  Table 17

Regional insulation R-values and air leakage characteristics of old house constructions built in 1980 (data taken from the 2006 database of NRCan’s Office of Energy Efficiency). ......... 106 

Table 18

Details of the simulated window types. Note that the performance metrics are calculated for a standard size window (0.6 m wide x 1.5 m tall). ..................................................................... 107 

Table 19 Detailed descriptions of the simulated shading devices. ........................................................... 109  Table 20 Hourly interior heat gains of the simulated model house. .......................................................... 111  10

LIST OF RELATED PUBLICATIONS JOURNAL AND CONFERENCE PAPERS Laouadi A. 2009. Thermal performance modeling of complex fenestration systems. Journal of Building Performance Simulation, 2(3): pp.189 — 207. Laouadi A. 2009. Thermal modeling of shading devices of windows. ASHRAE Transactions, pp. 803 - 814, 2009. Galasiu A.D., Laouadi A., Armstrong M., Swinton M.C., Szadkowski F. 2009. Field summer performance of interior reflective screen shades for residential windows. 11th IBPSA’s building simulation conference; Glasgow, Scotland; July 27-30, 2009; pp. 1642-1649. Laouadi A., Galasiu A.D., Swinton M.C., Armstrong M., Szadkowski F. 2009. Field performance of exterior solar shadings for residential windows: Summer results. 12th Canadian Conference on Building Science and Technology; Montréal, Quebec, May 2009; pp. 197-210. Laouadi A., Galasiu A.D., Swinton M.C., Manning M.M., Marchand R.G., Arsenault C.D., Szadkowski F. 2008. Field performance of exterior solar shadings for residential windows: Winter results. IBPSA-Canada eSim Conference (Quebec City, May 20, 2008); pp. 1-8.

TRADE MAGAZINES Laouadi A., Galasiu A.D. July 2009. Solar shading devices save energy in houses. Home Builder Magazine 2(3), pp. 1-3. URL: http://www.nrc-cnrc.gc.ca/obj/irc/doc/pubs/nrcc51405.pdf Laouadi A., Galasiu A.D. June 2009. Effective solar shading devices for residential windows save energy and improve thermal conditions. Lighting Design and Application (LD+A), June 2009, pp. 18-22. Laouadi A., Galasiu A.D. Spring/Summer 2009. Exterior residential rollshutters reduce summer energy demand by 26 percent. The Innovator, 2(1); pp. 4. Laouadi A., Galasiu A.D. 2009. Des pare-soleil pour réduire l’énergie de refroidissement de votre maison. Solplan Review, 144. pp. 18-19. Laouadi A., Galasiu A.D. 2009. Window shadings reduce residential cooling energy. Solplan Review; 144. pp. 18-19. Laouadi A. December 2007. Guidelines for effective solar shading of residential windows to be developed. Construction Innovation; 12(4). pp. 9. URL: http://irc.nrccnrc.gc.ca/pubs/ci/v12no4/v12no4_13_e.html Laouadi A. Décembre 2007. De nouvelles lignes directrices pour les dispositifs pare-soleil des fenêtres résidentielles. Innovation en construction, 12(4): pp. 9. URL: http://irc.nrccnrc.gc.ca/pubs/ci/v12no4/v12no4_13_f.html

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EXECUTIVE SUMMARY This study presents guidelines for the effective use of solar shading devices installed on residential windows under typical Canadian cold climates. The study addresses: thermal peak loads and energy use of old, current and future low or net-zero energy Canadian houses; energy costs and payback periods; thermal and visual comfort conditions near windows; potential risk of moisture condensation on the interior surfaces of windows; and excessive thermal stresses of window glass panes. Statistics published by Natural Resources Canada estimate that the energy use for heating and cooling accounts for about 63% of the total energy use of the average Canadian home (NRCan, 2006). Although the annual energy use for cooling is much lower than that for heating, many populated areas experience a peak electricity demand for air-conditioning on hot summer afternoons. Effective solar shading devices such as exterior shadings, highly-reflective between-pane or interior shadings are expected to reduce the heating and cooling energy use and the on-peak thermal loads, as well as to improve the thermal comfort conditions near windows. Exterior and between-pane shading devices are not common in Canada, but they may outperform the ubiquitous interior shading devices. There is little detailed information available on how different types of shading devices affect the residential energy use, peak cooling power demand, thermal and visual comfort of household occupants seated near windows, and the risk of moisture condensation on the interior surfaces of windows, when the shading devices are combined with conventional and high performance windows of old, current or future construction types of houses. Furthermore, the effect of the householders’ control of the shading devices and indoor climate on the house energy use is unknown. The model house used in this study was a typical two-storey building with a basement space, oriented in the north-south direction (with extensive windows on the south and north facades, and minimum windows on the east and west facades). The R-2000 construction standard was used for the current and future house types. Various combinations of window and shading device types were considered. Window types included conventional windows for the old type of houses, and high performance windows for the current and future types of houses. Shading devices included: typical interior blinds (the most widely used type of shading devices in Canada); interior highly-reflective metallic blinds; interior highly-reflective closedweave screen shades; between-pane highly-reflective metallic blinds; exterior insulating rollshutters; and exterior closed-weave screen shades. Four Canadian cities were selected to study the energy performance of each selected window and shading device combination: Ottawa (Ontario), Montreal (Quebec), Winnipeg (Manitoba), and Halifax (Nova Scotia). The guidelines were developed using wholebuilding energy computer simulations with inputs from a survey on householders’ usage and control of shading devices (Veitch et al., 2009), and field energy performance data collected for the selected shading devices (Laouadi et al., 2008; Laouadi et al., 2009; Galasiu et al., 2009). The computer simulation model was successfully validated using experimental data from the field measurement. These guidelines may assist homeowners and building developers in the selection of energy-efficient and cost-effective shading and window systems for renovations of old houses, or for building new low-energy houses. To this end, several performance metrics were developed, encompassing the performance of the shading and window system before and after its installation in houses, as well as its payback return period. Due to the various performance metrics, a proper selection of a shading and window system often requires a trade-off among the energy performance and the cost of the shading device, the visual and thermal comfort of the house occupants, and the aesthetic considerations. The following findings are highlighted:

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As traditionally proclaimed, windows with high solar heat gains and low U-factors are the best candidates for all construction types of houses in cold climates, providing higher annual total energy savings. For both old and current construction types of houses, double green windows (glazing SHGC = 0.48; glazing U-Factor = 2.79 W/m2K) are not as suitable compared with double clear windows (despite their significant potential to reduce the cooling energy by 22% to 33%, and summer peak cooling power demand by more than 11%) as they increase the house heating energy use and, hence, the annual total energy cost. Double clear windows with low-e coatings and argon gas (SHGC = 0.65; U-Factor = 1.67 W/m2K) are a more cost-effective option for the renovation of old houses, or for new houses when compared, for example, with triple clear super low-e windows (SHGC = 0.36; U-Factor = 0.94 W/m2K). Triple clear reflective (with a sandwiched heat mirror polyester film HM88) low-e windows (SHGC = 0.47; U-Factor = 0.66 W/m2K) are another good, but expensive renovation option for old construction types of houses, or for future low-energy or net-zero energy houses. Note that windows with typical interior blinds (the most widely used type of shading devices in Canada) are not particularly energy-efficient nor cost–effective compared to un-shaded windows, but they may still reduce the house cooling energy use and the on-peak cooling power demand (by up to 12%). Of course, they are used for many other reasons, primarily for privacy, glare and solar heat control. Exterior insulating rollshutters and close-weave screens are the most effective shading devices to reduce the house heating and cooling energy use, the on-peak cooling power demand, the risk of moisture condensation on the interior surfaces of windows, and the thermal discomfort conditions near windows (e.g., in winter, window interior surface temperatures are several degrees higher with rollshutters than with typical interior blinds). Rollshutters and screens are more effective when used with conventional windows (such as double clear windows) than when used with high performance windows. Their effect on the house total energy use is, however, not significant when they are used with super high performance windows (with U-factors < 1 W/m2K). They are worthwhile to consider in renovations of vertical windows of old houses, particularly in regions where the risk of ice build-up on their surfaces is minimum and does not hinder their operation (rollshutters are not recommended for installation on roof windows). When compared with typical interior blinds of old houses with conventional double clear windows, rollshutters may reduce the annual heating energy use by 7%, the cooling energy use by more than 40%, and the on-peak cooling power demand by 18% to 42% (30% on average). For R-2000 houses with double clear low-e windows, rollshutters may reduce the annual heating energy use by 6%, the cooling energy use by more than 53%, and the on-peak cooling power demand by 29% to 48% (39% on average). The total annual energy cost savings depend on the house construction and the prevailing regional fuel cost, and may vary from $163 (Winnipeg, MB) to $385 (Halifax, NS) for old houses when compared with typical interior blinds. The cost savings for R-2000 houses are lower than those for old houses. Indoor relative humidity may be raised up to 40% during cold winter days (compared to 30% for un-shaded windows) without causing any significant moisture condensation on the interior window glass surfaces. However, for the time being, exterior rollshutters and screens are expensive shading devices and their payback return periods are long (more than 38 years), often exceeding their lifespan periods. When compared with typical interior blinds, between-pane reflective metallic blinds are not as energy efficient nor as cost-effective because they increase the house annual heating energy use and cost (by up to 16%), particularly when integrated in high performance windows. Despite their significant potential to reduce the house annual cooling energy use (by more than 40%), and the on-peak cooling power demand (by 30% to 40%; 35% on average), they are not recommended for use in Canadian residences for the purpose of annual energy savings, although they may have other benefits. If such metallic blinds have to be integrated in windows for one reason or another, they should be incorporated in triple pane windows, and be completely retracted from the window area when open (as opposed to leaving their slats

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horizontal along the window area), in order to reduce the effect of thermal bridges and increase the admission of solar heat gains indoors in the winter. Furthermore, to improve their energy performance, the use of alternative blind slat materials with low thermal conductivity (such as fibreglass, wooden or plastic) is recommended in their construction. When compared with typical interior blinds, interior reflective, close-weave screens (having a low emissivity coating on the reflective surface) are effective shading devices, particularly to reduce the house annual cooling energy use and cost (by up to 25%) and the on-peak cooling power demand (by 13% on average), without negatively affecting the heating energy use. The total annual energy cost savings may vary from $68 (Winnipeg, MB) to $132 (Halifax, NS) for old houses. The cost savings for R-2000 houses are lower than those for old houses. Furthermore, the reflective screens would not result in excessive risk of thermal glass breakage due to high glass temperatures if the air space between the shades and the window is well ventilated (naturally or mechanically). However, such screens may exacerbate the risk of moisture condensation on the interior surfaces of windows (indoor relative humidity should be lower than 15% to avoid moisture condensation during winter cold days). The cheapest brands of such screens could be cost-effective, particularly if they are installed in old houses in cities with high fuel costs such as Halifax. The payback return period for old houses may range from 16 years for Halifax (highest fuel cost) to 32 years for Winnipeg (cheapest fuel cost). Interior reflective blinds are also effective shading devices, particularly to reduce the house cooling energy use and cost (by up to 15%), and the on-peak cooling power demand (7% on average), but they are not cost-effective when compared with typical interior blinds. Metallic blinds would not significantly increase the risk of moisture condensation on the interior window surface, and would not result in excessive risk of high glass temperatures and thermal glass breakage if the air space between the blinds and the window is well ventilated (as is the case when the blinds are mounted on the window frames, not inside the frames). To reduce their effect on the heating energy use, the blinds should be operated in such a manner that they are completely retracted from the window area when open in the winter (instead of drawn down with slats horizontal) to increase the admission of solar heat gains indoors.

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SOMMAIRE Cette étude présente des lignes directrices en vue d’une utilisation efficace des dispositifs pare-soleil installés dans les fenêtres des habitations canadiennes sous des climats froids typiques. L’étude a adressé les charges thermiques de pointe et la consommation énergétique des maisons canadiennes existantes (modèle de 1980), neuves ou futures à consommation énergétique nette zéro ou faible, le coût de l’énergie et les périodes de recouvrement des coûts, le confort thermique et visuel près des fenêtres, le potentiel de condensation de l'humidité sur les surfaces intérieures des fenêtres et les contraintes thermiques excessives sur les vitrages. Des statistiques de Ressources Naturelles Canada montrent que l’énergie servant au chauffage et à la climatisation représente environ 63 % de la consommation énergétique totale dans une maison canadienne moyenne (RNCan 2006). Bien que la quantité annuelle d’énergie servant à la climatisation soit encore très inférieure à la quantité d’énergie utilisée pour le chauffage, on observe dans de nombreuses régions habitées des pointes de consommation d'électricité durant les chauds après-midi d'été. Des dispositifs pare-soleil efficaces, comme des volets isolants extérieurs, des stores réfléchissants installés entre les vitrages et des stores réfléchissants intérieurs, devraient réduire la consommation énergétique de chauffage et de climatisation, ainsi que les charges thermiques de pointe, et améliorer le confort thermique près des fenêtres. Les dispositifs pare-soleil extérieurs et les dispositifs pare-soleil installés entre les vitrages, bien que peu répandus au Canada, pourraient offrir un rendement supérieur à celui des omniprésents dispositifs pare-soleil intérieurs. Nous disposons de peu de renseignements détaillés sur la façon dont les différents types de pare-soleil influent sur la consommation énergétique des habitations, la consommation énergétique de refroidissement de pointe, le confort thermique et visuel des occupants assis près des fenêtres, et le risque de condensation de l’humidité sur les surfaces intérieures des fenêtres lorsque les dispositifs pare-soleil sont combinés aux fenêtres classiques ou à haut rendement des maisons des types de construction existants, nouveaux ou futurs. De plus, l’effet que peut avoir la commande des pare-soleil et du climat intérieur par les occupants sur la consommation énergétique des maisons est inconnu. La maison modèle utilisée dans cette étude était un bâtiment typique de deux étages avec un espace sous-sol, orienté vers la direction nord-sud (avec beaucoup de fenêtres sur les façades sud et nord et un minimum de fenêtres sur les façades est et ouest). La norme de construction R-2000 a été utilisée pour les types de maisons neuves et futurs. Différentes combinaisons de types de fenêtre et de dispositif paresoleil ont été étudiées. Les types de fenêtres utilisés ont inclus les fenêtres classiques pour les maisons existantes, et les fenêtres à haut rendement pour les maisons neuves et futures. Les dispositifs paresoleil utilisés ont inclus les stores intérieurs types (le type de dispositifs pare-soleil le plus répandu au Canada), les stores intérieurs réfléchissants en métal, les toiles à armure serrée intérieures réfléchissantes, les stores métalliques réfléchissants installés entre les vitrages, les volets isolants extérieurs et les toiles à armature serrée extérieures. Quatre villes canadiennes ont été choisies en vue de l’étude du rendement énergétique de chaque combinaison de fenêtres et de dispositifs pare-soleil : Ottawa (Ontario), Montréal (Québec), Winnipeg (Manitoba) et Halifax (Nouvelle-Écosse). Les lignes directrices ont été élaborées au moyen de simulations informatiques de la consommation énergétique des bâtiments réalisées à partir des résultats d’un sondage sur l’utilisation des dispositifs pare-soleil par les occupants (Veitch et coll., 2009) et des données sur le rendement énergétique sur le terrain recueillies pour les dispositifs pare-soleil choisis (Laouadi et coll., 2008; Laouadi et coll., 2009; Galasiu et coll., 2009). Le modèle de simulation informatique utilisé dans l’étude a été validé au moyen de données expérimentales tirées des mesures sur le terrain.

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Ces lignes directrices peuvent aider les propriétaires de maison et les promoteurs immobiliers à choisir des systèmes de dispositifs pare-soleil et de fenêtres éconergétiques et économiques en vue de la rénovation des maisons existantes ou de la construction de maisons neuves à faible consommation énergétique. À cette fin, plusieurs mesures du rendement ont été élaborées, y compris le rendement du système de dispositifs pare-soleil et de fenêtres avant et après son installation dans les maisons, ainsi que la période de recouvrement des coûts. En raison des différentes mesures du rendement, la sélection d’un système approprié de dispositifs pare-soleil et de fenêtres exige souvent un compromis entre la performance énergétique et coût du système d’une part, et le confort visuel et thermique des occupants et les considérations esthétiques d’autre part. Les constatations suivantes ont été tirées de l’étude. Comme on le proclame depuis longtemps, les fenêtres à gain solaire élevé et faible facteur U sont les fenêtres les mieux adaptées à tous les types de construction de maison dans les climats froids, et permettent des économies d’énergie annuelles plus élevées. Pour les maisons tant existantes que neuves, les vitrages doubles verts (SHGC des vitrages = 0,48; facteur U des vitrages = 2,79 W/m2K) sont moins bien adaptés que les vitrages doubles clairs (malgré leur potentiel important de réduction de l’énergie de refroidissement de 22 % à 33 % et de la consommation énergétique de refroidissement estival de pointe de plus de 11 %), car ils augmentent les besoins en chauffage de la maison et, de ce fait, le coût annuel total de la consommation énergétique. Les vitrages doubles clairs à enduit à faible émissivité remplis d’argon (SHGC = 0,65; facteur U = 1,67 W/m2K) sont une option plus économique pour la rénovation des maisons existantes ou la construction des maisons neuves que, par exemple, les vitrages triples clairs à super faible émissivité (SHGC = 0,36; facteur U = 0,94 W/m2K). Les vitrages triples clairs réfléchissants (à miroir thermique constitué d’une pellicule de polyester HM88) à faible émissivité (SHGC = 0,47; facteur U = 0,66 W/m2K) sont une autre bonne, mais dispendieuse, option pour la rénovation des maisons existantes ou la construction des maisons futures à faible consommation énergétique ou consommation énergétique nette zéro. Il est à noter que les fenêtres à store intérieur type (le type de dispositif pare-soleil le plus répandu au Canada) ne sont pas particulièrement éconergétiques ni économiques, comparativement aux fenêtres non protégées, mais les stores peuvent quand même réduire la consommation énergétique de refroidissement de la maison et la consommation énergétique de refroidissement de pointe (jusqu’à 12 %). Évidemment, ils sont utilisés pour de nombreuses autres raisons dont, notamment, la protection de l’intimité, la protection contre l’éblouissement et la réduction de la chaleur. Les toiles à armature serrée et les volets isolants extérieurs sont les dispositifs pare-soleil qui réduisent le plus efficacement la consommation énergétique de chauffage et de refroidissement d’une maison, la consommation énergétique de refroidissement de pointe, le risque de condensation de l’humidité sur les surfaces intérieures des fenêtres et le confort thermique près des fenêtres (p. ex. les températures des surfaces intérieures des fenêtres sont de plusieurs degrés plus élevées lorsque des volets sont utilisés, par rapport aux stores intérieurs types). Les volets et les toiles sont plus efficaces lorsqu’ils sont utilisés avec des fenêtres classiques (comme les fenêtres claires à doubles vitrages) plutôt qu’avec des fenêtres à haut rendement. Leur effet sur la consommation énergétique totale de la maison n’est pas significatif lorsqu’ils sont utilisés avec des fenêtres à rendement super élevé (à facteur U < 1 W/m2K). Leur utilisation mérite d’être considérée pour les rénovations de fenêtres verticales de maisons existantes, en particulier dans les régions où le risque d’accumulation de glace sur les surfaces des volets et toiles est minimal, et ne gêne pas le fonctionnement de ces derniers (l’installation de volets sur les tabatières n’est pas recommandée). Comparativement aux stores intérieurs types utilisés dans les maisons existantes à fenêtres à doubles vitrages classiques, les volets peuvent réduire la consommation énergétique de chauffage annuelle de 7 %, la consommation énergétique de refroidissement de plus de 40 % et la consommation énergétique de refroidissement de pointe de 18 % à 42 % (30 % en moyenne). Pour les

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maisons R-2000 à fenêtres claires à doubles vitrages à faible émissivité, les volets peuvent réduire la consommation énergétique de chauffage annuelle de 6 %, la consommation énergétique de refroidissement de plus de 53 % et la consommation énergétique de refroidissement de pointe de 29 % à 48 % (39 % en moyenne). Les économies annuelles totales des coûts en énergie dépendent de la construction de la maison et du coût du combustible qui prévaut dans la région, et peuvent aller de 163 $ (Winnipeg (Manitoba)) à 385 $ (Halifax (N.-É.)) pour les maisons existantes, comparativement aux stores intérieurs types. Les économies de coût pour les maisons R-2000 sont inférieures aux économies possibles pour les maisons existantes. L’humidité relative intérieure peut être élevée jusqu’à 40 % au cours des journées froides d’hiver (comparativement à 30 % pour les fenêtres non protégées) sans causer de condensation importante de l’humidité sur les surfaces vitrées intérieures des fenêtres. Pour le moment toutefois, les toiles et les volets extérieurs sont des dispositifs dispendieux et leur période de recouvrement des coûts est longue (plus de 38 ans), dépassant souvent leur durée de vie. Comparativement aux stores intérieurs types, les stores métalliques réfléchissants entre les vitrages ne sont pas aussi éconergétiques ni aussi économiques parce qu’ils augmentent les coûts de chauffage annuels et la consommation énergétique de chauffage annuelle de la maison (de jusqu’à 16 %), en particulier lorsqu’ils sont intégrés à des fenêtres à haut rendement. Malgré leur potentiel important de réduction de la consommation énergétique de refroidissement annuelle des maisons (de plus de 40 %) et de la consommation énergétique de refroidissement de pointe (de 30 % à 40 %; 35 % en moyenne), leur utilisation n’est pas recommandée dans les maisons canadiennes pour réduire les coûts annuels de l’énergie, quoiqu’ils puissent présenter d’autres avantages. Si de tels stores métalliques doivent être intégrés à des fenêtres pour une raison ou une autre, ils devraient être incorporés à des fenêtres à triples vitrages et être complètement relevés lorsqu’ils sont ouverts (plutôt qu’être seulement en position horizontale le long de la fenêtre), de manière à réduire l’effet des ponts thermiques et augmenter l’admission des gains thermiques à l’intérieur en hiver. En outre, pour améliorer le rendement énergétique de ces stores, l’utilisation de matériaux à faible conduction thermique (comme la fibre de verre, le bois ou le plastique) est recommandée pour les lamelles. Comparativement aux stores intérieurs types, les toiles intérieures réfléchissantes à armature serrée (dotées d’un enduit à faible émissivité sur leur surface réfléchissante) sont des dispositifs pare-soleil efficaces, en particulier pour réduire le coût de l’énergie de refroidissement et la consommation de refroidissement annuelle de la maison (de jusqu’à 25 %), ainsi que la consommation énergétique de refroidissement de pointe (de 13 % en moyenne), sans avoir un effet négatif sur la consommation énergétique de chauffage. Les économies annuelles totales du coût de l’énergie peuvent aller de 68 $ (Winnipeg (Manitoba)) à 132 $ (Halifax (N.-É.)) pour les maisons existantes. Les économies de coût sont plus faibles pour les maisons R-2000 que pour les maisons existantes. De plus, les toiles réfléchissantes ne mèneraient pas à un risque excessif de bris des vitrages en raison de la température élevée de ces derniers si l’espace entre la toile et la fenêtre est bien ventilé (naturellement ou mécaniquement). Ces toiles peuvent toutefois augmenter le risque de condensation de l’humidité sur les surfaces intérieures des fenêtres (l’humidité relative intérieure devrait être inférieure à 15 % pour éviter la condensation de l’humidité au cours des journées froides d’hiver). Les marques de toile les moins dispendieuses pourraient être économiques, en particulier si elles sont installées dans des maisons existantes dans des villes où le coût du combustible est élevé, comme Halifax. La période de recouvrement des coûts pour les maisons existantes peut aller de 16 ans pour Halifax (coût du combustible le plus élevé) à 32 ans pour Winnipeg (coût du combustible le plus bas). Les stores réfléchissants intérieurs sont également des dispositifs pare-soleil efficaces, en particulier pour réduire le coût de l’énergie de refroidissement et la consommation énergétique de refroidissement de la maison (de jusqu’à 15 %), ainsi que la consommation énergétique de refroidissement de pointe (7 % en

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moyenne), mais ils ne sont pas économiques par rapport aux stores intérieurs types. Les stores métalliques n’augmenteraient pas de façon importante le risque de condensation de l’humidité sur la surface intérieure des fenêtres, et n’entraîneraient pas un risque excessif de températures élevées des vitrages et de bris d’origine thermique des vitrages si l’espace entre le store et la fenêtre est bien ventilé (comme cela est le cas lorsque les stores sont montés sur les cadres des fenêtres et non à l’intérieur des cadres). Pour réduire leur effet sur la consommation énergétique de chauffage, les stores doivent être complètement relevés lorsqu’ils sont ouverts en hiver (plutôt qu’être en position horizontale le long de la fenêtre), de manière à augmenter l’admission des gains thermiques à l’intérieur.

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INTRODUCTION Energy use for heating and cooling accounts for 63% of the total energy consumption of average Canadian homes (NRCan, 2006). Although the overall cooling energy demand is much lower than that for heating, many populated areas experience a peak demand for electricity on hot summer afternoons. Effective solar shadings of windows are expected to reduce the energy demand for heating and cooling and the peak thermal loads, and to improve the thermal comfort conditions near windows. They may include operable, exterior insulating rollshutters and screen shades, between-pane highly-reflective blinds, and interior highly-reflective blinds or screen shades. They potentially reduce solar overheating in summer and heat losses through windows in winter, and improve the thermal comfort of the house occupants seated near windows. However, if not properly designed and installed, shadings may increase the potential risk for moisture condensation on a window’s interior surface in winter (particularly when used with conventional windows in old house constructions), and generate excessive glass thermal stresses in summer (particularly when used with modern high performance windows). Moisture condensation on windows is not unusual in Canadian houses (NRCan, 2003) and is a major factor for mould and mildew growth, with their associated consequences for occupant health, and maintenance of and damage to building envelopes. Interior shadings are common in Canadian residential buildings and houses. Homeowners use interior shadings for various purposes such as window decoration, control of privacy, glare and summer overheating, and furniture fading protection. Field observations show that the use of highly reflective solar shadings is very limited, likely due to a lack of occupant awareness towards their energy saving potential, or because of other reasons such as cost and aesthetics. Between-pane blinds have been available in the market for commercial buildings, but have very limited use in houses. They are particularly used in clean rooms, hospitals and schools where the maintenance of interior shades is costly and problematic. Recently, between-pane blinds have received great market attention as affordable products to substitute the emerging smart windows, which have very limited market penetration due to high capital costs. Exterior shadings are common in Europe and some countries offer tax incentives for their installation in dwellings (e.g. France; MINEFI, 2005). In Canada, the use of exterior shadings is, however, very limited, but is expected to gain momentum in the future to combat the ever-increasing potential of overheating in summer due to the effects of climate change. Despite the promising effects of window solar shadings, there is little detailed information available on how the different types of shadings, when combined with different types of windows of old, current or future house constructions, affect the thermal and visual comfort of the house occupants seated near windows, and the thermal peak loads and energy use of houses. Furthermore, the shading usage patterns and control by the house occupants complicates the evaluation of the true energy use of occupied houses. In many cases, the occupants may use the shadings in an energy-inefficient way to achieve other goals, such as to maintain a view-out or to provide a desired level of daylight. Knowing such shading effects and the implications resulting from the occupants’ behaviour is important for both a sustainable design of new or future houses (where high performance windows are becoming the standard), and for the retrofitting of old buildings (which employ conventional windows). According to the IEA-Annex 50 (IEA, 2007), the future trend of energy conservation in buildings will focus on old building stocks, as the latter will consume about 80% of the total energy in industrialized countries. Recent surveys compiled by the Net Zero Energy Buildings Coalition (NZEB) showed that about 66% of house stocks in Canada will need retrofitting by 2030 to achieve the goals of the NZEB.

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OBJECTIVES The main goal of this study was to develop guidelines for the effective use of exterior, between-pane and interior solar shading devices of residential windows. The guidelines were developed based on wholebuilding energy computer simulations with inputs from field measurements of shading energy performance and a survey on Canadian householders’ control of indoor climate. The specific objectives were: • •

•

•

To develop performance metrics to compare various types of shading device and window combinations for Canadian residences; To assess the effects of selected shading devices and window type combinations on the thermal and visual comfort of occupants seated near windows; the risk of moisture condensation on the window interior surfaces; and the risk of excessive thermal stresses on the window glass panes. To assess the effects of selected shading device and window type combinations on the thermal peak loads and energy use for cooling and heating of old, current, and future low-energy (or net-zero energy) houses in selected Canadian cities. To evaluate the energy cost and payback periods resulting from the installation of various types of solar shading devices in retrofit or new homes.

PERFORMANCE METRICS OF WINDOW AND SHADING SYSTEMS Performance metrics of fenestration systems (window and shading systems) are essential in comparing and properly selecting fenestration products before their installation in buildings, and in understanding their expected performance after they are installed in real buildings. These performance metrics are usually calculated or measured under specific operating conditions set by relevant fenestration standards. It is expected, however, that these performance metrics would indicate or correlate with the actual performance of the fenestration system when installed in real buildings. For example, one would expect that the annual energy performance of a house would relate to the thermal and solar performance metrics of its windows. There are several performance metrics available for plain glass windows (without shading devices). These metrics include, for example, the visible transmittance, the solar heat gain coefficient and the thermal transmittance. However, there is a growing need to develop new metrics, particularly for complex windows with shading devices, in order to address the lighting performance and the visual and thermal comfort of the building occupants. Below, we list existing and new performance metrics of the window and shading device systems used in this study.

LIGHT DIFFUSION INDEX (HAZE) Haze is defined as the fraction of the scattered (or diffuse) component of the visible radiation energy transmitted through the fenestration system at a normal angle of incidence. The haze indicates the scattering power of a glazing system, and thus correlates with the ability (visibility or privacy) to see through the glazing system. Windows with clear glazing have haze values close to zero, whereas windows with fully translucent glazing (no see-through) have haze values close to 1. High values of haze are required by some building energy codes, particularly for diffusing skylights used in commercial buildings (see for example: ASHRAE 90.1 and CEC Title 24).

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VISIBLE TRANSMITTANCE (TVIS) TVIS is the ratio of the visible radiation energy entering the indoor space through the fenestration system to the visible radiation energy incident on the fenestration system plane at a normal angle, weighted by the photopic response of the human eye in the spectrum range 380 nm to 780 nm (ISO, 2003b). TVIS is expressed in decimal units or percentage. High values of TVIS are desirable to maximize daylight and reduce electrical lighting energy. However, high values of TVIS are usually accompanied by high values of TFD (see definition below).

ULTRA-VIOLET TRANSMITTANCE (TUV) TUV is the ratio of the ultra-violet radiation energy entering the indoor space through the fenestration system to the ultra-violet radiation energy incident on the fenestration system plane at a normal angle. TUV covers the radiation spectrum range from 300 nm to 380 nm (UV-A and UV-B) (ISO, 2003b). Low values of TUV are usually desirables to reduce the risk of fading of fabric materials.

FADING TRANSMITTANCE (TFD) TFD is the ratio of the radiation energy entering the indoor space through the fenestration system to the radiation energy incident on the fenestration system plane at a normal angle, weighted by the CIE (Commission Internationale de l’Éclairage) damage factor in the radiation spectrum range 300 nm to 600 nm (ISO, 2003b). Low values of TFD are desirable to reduce the potential risk of fabric material fading.

SKIN DAMAGE TRANSMITTANCE (TSD) TSD is the ratio of the radiation energy entering the indoor space through the fenestration system to the radiation energy incident on the fenestration system plane at a normal angle, weighted by the CIE erythemal effectiveness in the radiation spectrum range 300 nm to 400 nm (ISO, 2003b). Low values of TSD are desirable to reduce the risk of the radiation damage to people skin (or sunburns), particularly in summer where the concentration of the outdoor UV radiation is at its highest level.

SOLAR HEAT GAIN COEFFICIENT (SHGC) The SHGC is the ratio of the total solar radiation energy entering the indoor space through the fenestration system to the solar radiation energy incident on the fenestration system plane at a normal angle. The total radiation energy entering the indoor space includes the directly transmitted solar radiation energy and a fraction of the radiation energy absorbed by the fenestration glazing panes, which is subsequently released indoors as heat. The SHGC covers the radiation spectrum range from 300 nm to 2500 nm (UV, Visible, and near infrared). Window systems with high values of SHGC are desirable in heating-dominated regions, and those with low values of SHGC are desirable in cooling-dominated regions. In North America, the NFRC-200 standard (NRFC, 2004b) is used to compute the SHGC of window systems at outdoor and indoor temperatures of 32oC and 24oC, respectively, and a solar radiation intensity of 783 W/m2.

THERMAL TRANSMITTANCE OF GLAZING ASSEMBLY (U-FACTOR) The U-factor (W/m2K) of a glazing assembly (without the frame section) is the rate of the heat loss (or gain) through the glazing assembly per unit surface area, and unit temperature differential between the

21

inside and the outside air. The lower the U-factor, the better the insulating value of a fenestration system. The U-factor of a glazing assembly includes the heat loss through the centre and the edge sections of the glazing assembly. Windows with low U-factors are desirable in heating-dominated regions. The U-factor is calculated in the absence of solar radiation or any heat generation within the glazing panes. In North America, the NFRC-100 standard (NRFC, 2004a) is used to compute the U-factors of fenestration systems under night-time conditions when the outdoor and indoor temperatures are fixed at -18oC and 21oC, respectively, and the wind speed is 5.5 m/s.

THERMAL TRANSMITTANCE OF EDGE-OF-GLAZING (U- FACTOR -EDGE) The U-Factor of the edge-of-glazing assembly is the rate of the heat loss (or gain) through the edge section (defined as a band with a width of 6 mm off from the frame line) of the glazing assembly per unit surface area, and unit temperature differential from the inside to outside air. The U-factor of the edge-ofglazing takes into account the spacer type between the glazing panes. Insulating spacers of high performance windows have lower U-factors compared to metallic spacers, which are usually found in conventional windows.

LUMINANCE INDEX (LI) LI is defined as the ratio of the luminance of the interior surface of a fenestration system to the luminance of the interior surface of a clear reference fenestration system with 100% transmittance when the fenestration system sees the full sky vault (i.e., in a horizontal position) and the incident sunlight is normal to its plane (Laouadi and Parekh, 2007). To limit the potential glare from windows, LI should not exceed 0.29, 0.09, and 0.15 for overcast, partly cloudy and clear sky conditions, respectively. Values of LI greater than TVIS indicate that a light scattering fenestration system is seen brighter than a clear fenestration system with similar TVIS. The above LI thresholds for visual discomfort glare are based on a threshold window luminance of 2500 cd/m2 (Fisekis et al., 2003). Recent research found that more than 50% of office occupants would perceive discomfort glare from windows if their luminance exceeded 2100 cd/m2 (Clear et al., 2006).

VIEW-OUT INDEX (VOI) VOI is defined as the ability of a person situated indoors to see outdoor objects through the fenestration system under given indoor and outdoor lighting conditions during daytime. VOI is calculated for clear and sunny sky conditions when the fenestration system sees the full sky vault and the beam sunlight is almost normal to its plane. Under such clear sky conditions, indoor light levels would not affect the view-out through the fenestration system. VOI ≈ 1 applies to windows with clear glazing and VOI ≈ 0 applies to windows with fully translucent glazing. VOI values between 1 and 0 indicate that the view-out is partially impaired.

MOISTURE CONDENSATION INDICATOR Moisture condensation on the interior surfaces of windows is indicated by the threshold relative humidity (RH) of the indoor air above which the moist air may condensate on the edge-of-glazing and/or the centre-of-glazing sections of windows. The threshold relative humidity is calculated based on the window surface temperatures under specific indoor and outdoor environmental conditions.

22

Moisture condensation on the interior window surfaces is a common problem in Canadian residences. More than 41% of old and new houses were reported to have condensation on windows (NRCan, 2003; Veitch et al., 2009). Moisture condensation problems due to excessive indoor humidity levels can lead to window frame material damage, mould, mildew, and health problems (allergies). Likewise, low levels of indoor humidity may lead to health problems, such as skin dryness, scratchy nose and throat, and breathing problems. For comfortable and healthy indoor environments, CHMC recommends indoor relative humidity levels lower than 45% at 21oC in winter. In very cold weather, the indoor relative humidity should not exceed 30% (CMHC, 2008).

PERFORMANCE DATA OF WINDOW AND SHADING SYSTEMS Old and current Canadian residences use a variety of window types, ranging from conventional double glazed windows to high performance (with low-e coatings and gas fills) windows. While high performance windows have become the standard for new constructions, renovated old houses use a mixture of both window types. Recent trends in high performance buildings and net-zero-energy houses have more stringent requirements for windows with regard to the control of solar heat gains and heat losses. Super windows with triple or quadruple glazing and low-e coatings with U-Factors around 0.6 W/m2oC or lower are required to realize net-zero-energy houses (Arasteh et al., 2006). In this study, several types of conventional, high performance and super windows were considered. Conventional windows include double and triple clear glass windows that maximize daylight and solar heat gains, and double green glass windows, which control solar heat gains in summer while providing adequate daylight in winter. High performance windows include double clear glass with low-e coating and argon gas. Super high performance windows include triple clear glass windows with two low-e coatings, and double clear low-e glass windows with a between-pane solar reflective polyester heat mirror. Table 18 in Appendix A provides a detailed description of the simulated windows. Canadian residences typically use a variety of interior shading devices such as horizontal or vertical blinds, roller screens and draperies (Veitch et al., 2009). Although they are more effective than interior shading devices to control solar heat gains in summer and heat losses in winter, exterior or betweenpane (between window glass panes) shading devices are not common in Canadian residences. Three types of shading devices with potential energy savings were considered in this study. The selected shading devices may be placed outside or inside the windows, or between the window glass panes. The exterior shading devices include insulating rollshutters and black close-weave roller screens. The interior shading devices include highly reflective (white) close-weave roller screens, and highly reflective (white) and typical (light grey) horizontal blinds. The between-pane shading devices include highly reflective (white) horizontal blinds. Table 19 in Appendix A provides a detailed description of the simulated shading devices. The window and shading devices mentioned above were combined to study their overall effect on the energy performance of old and current construction types of houses. The performance metrics of standard-size window and shading device combinations (width = 0.6 m and height = 1.5 m) were calculated using a validated in-house version of SkyVision (NRC, 2006). Details on the SkyVision’s models for shading devices may be found in Laouadi (2009a,b). The NFRC standards 100 and 200 (NFRC, 2004a,b) and the ISO standards 15093 and 9050 (ISO, 2003a,b) were used to compute the performance metrics.

23

UN-SHADED WINDOWS The use of un-shaded windows is not unusual in Canadian residences. In fact, a significant number of householders (8% to 15%) reported that they did not use any shading on windows, particularly in the living and dining rooms (Veitch et al., 2009). Table 1 shows the calculated performance metrics for various un-shaded windows. Both conventional and high performance windows have excellent potential for daylight admission and view-out, and very low potential risk for skin radiation damage. However, all windows have high radiation risk for fading of house furniture. Furthermore, the occupants may perceive discomfort glare from the windows during daytime due to high window luminances (LI > 0.09). The use of appropriate shading devices may reduce or eliminate such issues. Both conventional and high performance windows may be used to control solar heat gain and heat losses. The proper selection of a window is dependent on the site location and the prevailing climate, whether it is heating or cooling dominated or both. For heating dominated climates such as in Canada, windows with high SHGC and low U-factors are appropriate choices. Details on the energy effect of such windows will follow in the next sections of this report. Figure 1 shows the profile of the threshold indoor relative humidity for moisture condensation on the interior surfaces of windows (centre and edge of glazing sections) under various outdoor temperature conditions when the indoor air temperature is set to 21oC. As expected, indoor moist air starts to condensate first on the edge of the glazing and then spreads to the centre area. To avoid potential moisture condensation on double glass conventional windows of old houses, the indoor relative humidity should be lower than 30% in moderately cold outdoor weather conditions (outdoor temperatures higher than -15oC), and lower than 20% in very cold outdoor weather conditions (outdoor temperatures higher than -30oC). The use of any indoor moisture generation equipment (such as humidifiers, showers, cooking) should, therefore, be carefully monitored according to the outdoor weather conditions to keep the indoor humidity below the threshold level. High performance windows significantly reduce the risk of moisture condensation on windows. The popular double clear low-e windows (DLCE) of current construction type of houses may form condensation when the indoor relative humidity at 21oC exceeds 40% under outdoor temperatures higher than -30oC. It is, therefore, possible to use humidifiers to improve the indoor air quality and reduce potential health problems. In extreme cold weather conditions (outdoor temperatures lower than -30oC), super windows (such as TCSE and TCME) would be appropriate not only to reduce the risk of moisture condensation, but also to reduce the heating energy use. It should be noted that the above results for moisture condensation on windows are valid when the indoor air temperature is set at the comfort value of 21oC. Higher set point temperatures would further reduce the risk of moisture condensation on windows, and therefore higher indoor relative humidity levels may be used. However, night-time temperature setback, which is commonly used in Canadian residences (Veitch et al., 2009), would exacerbate the risk of moisture condensation on windows since the temperature setback will increase the indoor air relative humidity and reduce the window surface temperatures (Tariku et al., 2008; Manning et al., 2005).

24

Table 1

Performance metrics of un-shaded windows (for the combined centre and edge of glass sections).

Æ

Performance

Metric

Conventional Windows

High Performance Windows

(with metallic spacers)

(with insulating spacers)

double clear

double green

triple clear

(DBLC)

(DBLG)

(TPLC)

double clear low-e

triple clear super low-e

(DLCE)

(TCSE)

triple clear reflective low-e (TCME)

TVIS

0.78

0.67

0.70

0.73

0.57

0.68

Haze

0

0

0

0

0

0

TUV

0.44

0.19

0.34

0.35

0.08

0.00

TFD

0.66

0.49

0.57

0.58

0.38

0.40

TSD

0.11

0.05

0.08

0.09

0.03

0.01

SHGC

0.70

0.48

0.61

0.65

0.36

0.47

U-Factor

2.79

2.79

1.96

1.67

0.94

0.66

U-FactorEdge

3.26

3.26

2.61

1.87

1.26

1.04

LI

0.78

0.67

0.70

0.73

0.57

0.68

1

1

1

1

1

1

VOI

25

100

un‐shaded windows

90

Relative Humidity (%)

80 70 60 50 40 30 20 10

DBLC: center

TPLC: center

DLCE: center

TCSE: center

TCME: center

DBLC: edge

TPLC: edge

DLCE: edge

TCSE: edge

TCME: edge

0 -5

-10

-15

-20

-25

-30

-35

-40

Outdoor Temperature ( C) O

Figure 1

Moisture condensation on the interior surfaces of un-shaded windows at an indoor temperature of 21oC.

WINDOWS WITH TYPICAL INTERIOR BLINDS Interior slat-type blinds are one of the most common shading devices in Canadian residences. An NRC household survey found that more than 30% of households use horizontal or vertical blinds (Veitch et al, 2009). There are many types of blinds with varying slat colours and materials (e.g., metallic, plastic, wooden). Typical interior blinds are metallic and grey in colour (solar reflectance 42%), and are situated between highly absorbing (dark colour) and reflecting (white) interior shading systems. Typical interior blinds were used in this study as the base case against which the performance of the other selected shading devices was compared to in terms of energy-efficiency and cost-effectiveness. Table 2 summarizes the performance metrics of windows with typical metallic blinds in open and closed positions. When open (slat angle = 0o, horizontal), the blinds do not significantly affect the window optical (at a normal incidence angle) and thermal performance, and particularly the view-out, daylight admission, solar heat gains and heat losses. When the blinds are closed (slat angle = 75o), they may, however, reduce the solar heat gains through the windows, from 40% (with high performance windows) to 50% (with conventional windows) when compared with un-shaded windows. There is no noticeable effect of the interior blinds on the heat loss through the windows, and the moisture condensation on the interior window surfaces (compare Figure 1 with Figures 2 and 3). This is because the air space between the

26

 

blinds and the window is naturally ventilated through the deliberate opening left between the slats, and at the side, top and bottom ends.

Table 2

Performance metrics of windows with interior typical blinds (for the combined centre and edge of glass sections).

Performance Metric

Conventional Windows

double clear

High Performance Windows

triple clear

double green

(DBLC)

double clear low-e

triple clear super low-e

(DLCE)

(TCSE)

(TPLC) (DBLG)

triple clear reflective low-e (TCME)

Æ

closed

open

closed

open

closed

open

closed

open

closed

open

closed

open

TVIS

0.03

0.71

0.02

0.60

0.03

0.63

0.03

0.66

0.02

0.52

0.02

0.61

Haze

1

0.01

1

0.01

1

0.02

1

0.01

1

0.02

1

0.02

TUV

0.00

0.40

0

0.17

0.00

0.31

0.00

0.31

0

0.07

0

0.00

TFD

0.02

0.59

0.01

0.44

0.02

0.51

0.02

0.52

0.01

0.34

0.01

0.36

TSD

0

0.10

0

0.04

0

0.07

0

0.08

0

0.02

0

0.01

SHGC

0.34

0.67

0.26

0.47

0.34

0.58

0.37

0.63

0.21

0.34

0.28

0.46

U-Factor

2.77

2.88

2.76

2.88

1.93

1.99

1.63

1.68

0.93 0.94

0.66

0.66

U-FactorEdge

3.25

3.38

3.25

3.38

2.6

2.67

1.83

1.88

1.24

1.27

1.03

1.04

LI

0.05

0.73

0.05

0.62

0.05

0.66

0.05

0.68

0.04

0.54

0.05

0.63

0

0.94

0

0.94

0

0.94

0

0.94

0

0.94

0

0.94

VOI

 

27

100

windows with interior blinds (open)

90

Relative Humidity (%)

80 70 60 50 40 30 20 DBLC: center

TPLC: center

DLCE: center

TCSE: center

TCME: center

DBLC: edge

TPLC: edge

DLCE: edge

TCSE: edge

TCME: edge

10 0 -5

-10

-15

-20

-25

-30

-35

Outdoor Temperature ( C)

-40

O

Figure 2

Moisture condensation on the interior surfaces of windows with interior typical blinds in an open position when the indoor temperature is set at 21oC.

28

 

100

windows with interior blinds (closed)

90

Relative Humidity (%)

80 70 60 50 40 30 20 DBLC: center

TPLC: center

DLCE: center

TCSE: center

TCME: center

DBLC: edge

TPLC: edge

DLCE: edge

TCSE: edge

TCME: edge

10 0 -5

-10

-15

-20

-25

-30

-35

-40

Outdoor Temperature ( C) O

Figure 3

Moisture condensation on the interior surfaces of windows with interior typical blinds in a closed position when the indoor temperature is set at 21oC.

WINDOWS WITH INTERIOR REFLECTIVE BLINDS Table 3 summarizes the performance metrics of window combinations with reflective (white) metallic blinds in open and closed positions. When open, the reflective blinds do not significantly affect the window performance, particularly the view-out, daylight admission (at a normal incidence angle), solar heat gains (at a normal incidence angle) and heat losses. When closed, the blinds, however, can effectively reduce the solar heat gains through the windows, from 53% (with high performance windows) to 63% (with conventional windows) when compared with un-shaded windows. There is no noticeable effect of the interior reflective blinds on the heat loss through the windows, and the moisture condensation on the interior window surfaces.

29

 

Table 3

Performance metrics of windows with interior reflective metallic blinds (for the combined centre and edge of glass sections).

Performance Metric

Conventional Windows

double clear

High Performance Windows

triple clear

double green

(DBLC)

double clear low-e

triple clear super low-e

(DLCE)

(TCSE)

(TPLC) (DBLG)

triple clear reflective low-e (TCME)

Æ

closed

open

closed

open

closed

open

closed

open

closed

open

closed

open

TVIS

0.07

0.72

0.06

0.61

0.07

0.65

0.07

0.67

0.06

0.53

0.07

0.62

Haze

1

0.03

1

0.03

1

0.03

1

0.03

1

0.03

1

0.03

TUV

0.00

0.40

0.0

0.17

0.00

0.31

0.00

0.31

0

0.07

0

0.00

TFD

0.05

0.60

0.04

0.44

0.04

0.52

0.04

0.53

0.03

0.34

0.04

0.36

TSD

0.00

0.10

0

0.04

0

0.07

0

0.08

0

0.02

0

0.01

SHGC

0.26

0.67

0.22

0.46

0.28

0.58

0.30

0.63

0.17

0.34

0.22

0.45

U-Factor

2.76

2.88

2.76

2.88

1.93

1.99

1.63

1.68

0.93

0.94

0.65

0.66

U-FactorEdge

3.25

3.38

3.25

3.38

2.59

2.67

1.83

1.88

1.24

1.27

1.03

1.04

LI

0.15

0.78

0.12

0.66

0.14

0.70

0.14

0.72

0.11

0.57

0.13

0.67

0

0.88

0

0.88

0

0.87

0

0.87

0

0.87

0

0.87

VOI

  WINDOWS WITH INTERIOR REFLECTIVE SCREEN SHADINGS Interior roller screen shadings are common interior shading devices in Canadian residences (Veitch et al., 2009). There are many types of screen shadings with various fabric materials, colours and openness factors to control the solar heat gains and view-out (or privacy), but a few of them would be highly 30

reflective. Highly reflective screen shadings (the reflective surface faces the outside) require special installation to reduce the potential risk of glass breakage due to excessive window glass temperatures. This is particularly true if the reflective shadings are mounted inside the frames of high performance windows (e.g., DLCE) and the air space between the shade and the window is sealed (Manning et al., 2006). To avoid such undesirable effects, the air space between the shades and the window should be left open for natural or forced ventilation. Table 4 summarizes the performance metrics of window combinations with a reflective and close-weave screen shading (openness factor of 4%). The reflective surface facing the outside is made of an aluminium coating with a diffuse solar reflectance of 77% and a low emissivity of 13%. The other screen surface facing the indoor is painted white. When completely covering the window surface, the interior reflective screen shadings are an effective means to reduce the potential damage of solar radiation to house furniture and people skins, solar overheating in summer, and window glare luminances. Interior reflective screens may reduce the solar heat gains through windows from 55% (with high performance windows) to 67% (with conventional windows) when compared with un-shaded windows. The screens provide an acceptable view through windows, particularly when the windows are not exposed to direct sunlight (e.g., north windows; see Figure 4). Direct sunlight incident on windows (e.g., south windows) slightly impairs the view through windows due to the screen light scatter effect (haze < 9%). Due to their low emissivity, interior screens may reduce the heat loss through windows from 16% to 20% when used with conventional windows, and by up to 16% when used with high performance windows.

  Figure 4

View-out through a double clear low-e window (DLCE) with an interior reflective roller screen shade.

Figure 5 shows the profile of the threshold indoor relative humidity for moisture condensation on the interior surfaces of windows with interior reflective screen shadings when the indoor air temperature is fixed at 21oC. Interior screens (with low emissivity coating) exacerbate the risk of moisture condensation on the interior surfaces of windows. To avoid the potential moisture condensation on conventional windows of old houses, or high performance windows of current houses, the indoor relative humidity should be lower than 15% or 25%, respectively, in cold outdoor weather conditions (outdoor temperatures

31

higher than -30oC). These threshold humidity levels may occur in houses without humidifiers, and may result in indoor air quality and health problems. The use of humidifiers should therefore be carefully monitored to avoid excessive moisture condensation.

Table 4

Performance metrics of windows with interior reflective screen shadings (for the combined centre and edge of glass sections).

Performance Metric Æ

Conventional Windows

High Performance Windows

double clear

double green

triple clear

(DBLC)

(DBLG)

(TPLC)

double clear low-e

triple clear super low-e

(DLCE)

(TCSE)

triple clear reflective low-e (TCME)

TVIS

0.05

0.04

0.05

0.05

0.04

0.05

Haze

0.06

0.05

0.08

0.06

0.07

0.06

TUV

0.02

0.01

0.02

0.02

0.00

0.00

TFD

0.04

0.03

0.04

0.04

0.02

0.03

TSD

0.01

0.00

0.00

0.00

0.00

0.00

SHGC

0.23

0.19

0.24

0.27

0.16

0.21

U-Factor

2.23

2.23

1.65

1.40

0.84

0.61

U-FactorEdge

2.63

2.63

2.22

1.58

1.14

0.97

LI

0.08

0.06

0.07

0.07

0.06

0.07

VOI

0.81

0.82

0.77

0.81

0.79

0.80

32

100 90

DBLC: center

TPLC: center

DLCE: center

TCSE: center

TCME: center

DBLC: edge

TPLC: edge

DLCE: edge

TCSE: edge

TCME: edge

Relative Humidity (%)

80

windows with interior reflective screens 70 60 50 40 30 20 10 0 -5

-10

-15

-20

-25

-30

-35

-40

Outdoor Temperature ( C) O

Figure 5 Condensation on the interior surfaces of windows with interior screen shadings.

WINDOWS WITH BETWEEN-PANE REFLECTIVE BLINDS Between-pane blinds are available in the market for commercial buildings, but with very limited use in Canadian residences. They are used particularly in clean rooms, hospitals and schools where the maintenance of interior shades is costly and problematic. Typical commercial blinds have metallic horizontal slats (aluminium) to withstand high temperatures. The slats may be lifted up so that the window glass area is completely exposed to sunlight, or the slats may be just rotated around a horizontal axis parallel to the slats to control the view-through (and privacy) and block the direct sunlight admission indoors. Table 5 summarizes the performance metrics of windows with metallic reflective, white (solar reflectance of 70%) blind systems when the blinds are open (slats horizontal) and closed (slats rotated by 89o). In an open position, the blinds do not significantly affect the window performance, particularly the view-out, daylight admission, solar heat gains (at a normal incidence angle) and heat losses. When the blinds are closed, they effectively reduce the solar heat gains through the windows from 68% to 83% when compared with un-shaded windows. For heat loss control, metallic blinds are better when used with conventional windows (the U-factor is reduced by more than 15% compared to un-shaded windows), but have no noticeable effect when they are used with high performance windows. It must be emphasized that the use of metallic blinds may result in an undesirable thermal bridge effect between the interior and the exterior window glass panes, particularly when the slats are horizontal. The use of alternative slat materials with low thermal conductivity (such as fibreglass, wooden or plastic)

33

would reduce the thermal bridge effect. In fact, plastic slats may reduce the U-factor of both conventional and high performance windows by more than 20% (Laouadi, 2009a).

Table 5

Performance metrics of windows with between-pane reflective metallic blinds (for the combined centre and edge of glass sections).

Performance Metric

Conventional Windows

double clear

High Performance Windows

triple clear

double green

(DBLC)

double clear low-e

triple clear super low-e

(DLCE)

(TCSE)

(TPLC) (DBLG)

triple clear reflective low-e (TCME)

Æ closed

open

closed

open

closed

open

closed

open

closed

open

closed

open

TVIS

0.01

0.77

0.01

0.66

0.01

0.69

0.01

0.72

0.01

0.57

0.01

0.67

Haze

1

0.00

1

0.00

1

0.00

1

0.00

1

0.00

1

0.00

TUV

0

0.44

0

0.19

0

0.34

0

0.34

0

0.08

0

0.00

TFD

0.01

0.65

0.01

0.48

0.01

0.56

0.01

0.57

0.00

0.37

0.01

0.39

TSD

0

0.11

0

0.05

0

0.08

0

0.09

0

0.02

0

0.01

SHGC

0.12

0.69

0.13

0.47

0.17

0.60

0.09

0.64

0.11

0.35

0.15

0.48

U-Factor

2.18

2.66

2.18

2.65

1.65

1.89

1.68

2.04

0.94

1.03

0.78

0.84

U-FactorEdge

2.78

3.16

2.78

3.16

2.36

2.55

1.89

2.19

1.26

1.33

1.13

1.18

LI

0.02

0.81

0.02

0.69

0.02

0.73

0.02

0.75

0.02

0.59

0.02

0.70

0

0.95

0

0.95

0

0.95

0

0.95

0

0.95

0

0.95

VOI

34

Figures 6 and 7 show the profiles of the threshold indoor relative humidity for moisture condensation on the interior surfaces of windows with between-pane blinds in open and closed positions. The indoor air temperature is fixed at 21oC. Between-pane blinds increase the potential risk for moisture condensation on the interior surfaces of both conventional and high performance windows. To avoid moisture condensation on the double glass conventional windows of old houses, the indoor relative humidity should be lower than 20% in cold outdoor weather conditions (outdoor temperatures higher than -30oC). The use of any indoor moisture generation equipment or sources should, therefore, be carefully monitored according to the outdoor weather conditions to keep the indoor relative humidity below the threshold level. For current construction type of houses with high performance windows, the indoor relative humidity should be kept lower than 40%. It is, therefore, possible to use humidifiers to improve the indoor air quality and reduce the health problems associated with low relative humidity levels. 100

windows with between‐pane reflective blinds (open)

90

Relative Humidity (%)

80 70 60 50 40 30 20 DBLC: center

TPLC: center

DLCE: center

TCSE: center

TCME: center

DBLC: edge

TPLC: edge

DLCE: edge

TCSE: edge

TCME: edge

10 0 -5

-10

-15

-20

-25

-30

-35

-40

Outdoor Temperature (OC)

Figure 6

Moisture condensation on the interior surfaces of windows with between-pane metallic blinds in an open position when the indoor temperature is set at 21oC.

35

100

windows with between‐pane reflective blinds (closed)

90

Relative Humidity (%)

80 70 60 50 40 30 20 DBLC: center

TPLC: center

DLCE: center

TCSE: center

TCME: center

DBLC: edge

TPLC: edge

DLCE: edge

TCSE: edge

TCME: edge

10 0 -5

-10

-15

-20

-25

-30

-35

-40

Outdoor Temperature ( C) O

Figure 7

Moisture condensation on the interior surfaces of windows with between-pane metallic blinds in a closed position when the indoor temperature is set at 21oC.

WINDOWS WITH EXTERIOR ROLLSHUTTERS Insulating rollshutters are not commonly used in Canadian residences despite their potential to reduce house energy use. Rollshutters are opaque and installed on the outside walls containing the windows. Side rails with rubber gaskets are usually used to guide the vertical movement of the shutter and to partially seal the air space between the shutter and the window. When the shutters are completely closed (covering the whole window surface; see Figure 8), they totally block the admission of sunlight indoors and the view out. Table 6 summarizes the performance metrics of a window and shutter system. The performance metrics not listed in Table 6 are zero. Exterior rollshutters are an effective means to reduce solar overheating in summer and heat losses through windows in winter. For heat loss control, rollshutters are more effective with conventional windows than with high performance windows. When used with conventional windows of old houses, rollshutters may reduce the window U-factor by 33% (with TPLC) to 40% (with DBLC and DBLG). When used with high performance windows the U-factor reduction may vary from 15% (with TCME) to 30% (with DLCE). Rollshutters are, therefore, worthwhile to consider in renovating the vertical windows of old houses, particularly in cold climate regions where the risk of ice build-up on the shutter is minimum and does not hinder their operation (shutters are not recommended for installation on roof windows).

36

  Figure 8 Exterior rollshutter in a closed position.

Table 6 Performance metrics of windows with exterior rollshutters (for the combined centre and edge of glass sections). Performance Metric Æ

Conventional Windows

double clear

double green

(DBLC)

High Performance Windows

triple clear

double clear low-e

triple clear super low-e

(DLCE)

(TCSE)

(TPLC) (DBLG)

triple clear reflective low-e (TCME)

SHGC

0.04

0.04

0.04

0.03

0.02

0.02

U-Factor*

1.65

1.65

1.32

1.16

0.75

0.56

U-FactorEdge

1.84

1.84

1.64

1.27

0.97

0.85

*The calculation of the U-factors assumes the air space between the shutter and window is sealed. For partially unsealed air spaces, the U-Factors may be higher.

37

Figure 9 shows the profile of the threshold indoor relative humidity for moisture condensation on the interior surfaces of windows with rollshutters when the indoor air temperature is fixed at 21oC. When closed (during winter night-time), rollshutters significantly reduce the risk of moisture condensation on the interior surfaces of both conventional and high performance windows. To avoid potential moisture condensation on double glass conventional windows of old houses, the indoor relative humidity should be lower than 40% in cold outdoor weather conditions (outdoor temperatures higher than -30oC). For current construction type of houses with high performance windows, the indoor relative humidity should be kept lower than 45%. It is, therefore, possible to use humidifiers to improve the indoor air quality and reduce the health problems associated with low relative humidity levels. 100

windows with exterior rollshutters

90

Relative Humidity (%)

80 70 60 50 40 30 20 DBLC: center

TPLC: center

DLCE: center

TCSE: center

TCME: center

DBLC: edge

TPLC: edge

DLCE: edge

TCSE: edge

TCME: edge

10 0 -5

-10

-15

-20

-25

-30

-35

-40

Outdoor Temperature ( C) O

Figure 9

Moisture condensation on the interior surfaces of windows with exterior rollshutters when the indoor temperature is set at 21oC.

WINDOWS WITH EXTERIOR SCREEN SHADINGS Similarly to exterior rollshutters, exterior screen shadings are not commonly used in Canadian residences. There are many types of commercial exterior screen shadings with various fabric materials, colours and openness factors. Side rails are usually used to guide the vertical movement of the screen (see Figure 10). Table 7 summarizes the performance metrics of windows combined with black and close-weave (openness factor of 5%) screen shadings. When completely closed, exterior screen shadings are an effective means to reduce the solar radiation potential damage to house furniture and people skins, solar overheating in summer, and heat loss through windows in winter. Furthermore, the perforated screens effectively control the window glare luminances without significantly impairing the view through windows during daytime. For solar control, exterior screens may reduce the solar heat gains by more than 80%

38

 

when compared with un-shaded windows. For heat loss control, exterior screens are more effective with conventional windows than with high performance windows. When used with conventional windows of old houses, exterior screens may reduce the window U-factor by 25% to 32%. When used with high performance windows the U-factor reduction may vary from 12% to 24%. Table 7

Performance metrics of windows with exterior screen shadings (for the combined centre and edge of glass sections).

Performance

Metric

Conventional Windows

High Performance Windows

Æ

double clear

double green

triple clear

(DBLC)

(DBLG)

(TPLC)

double clear low-e

triple clear super low-e

(DLCE)

(TCSE)

triple clear reflective low-e (TCME)

TVIS

0.04

0.03

0.04

0.04

0.03

0.04

Haze

0.02

0.02

0.02

0.02

0.02

0.02

TUV

0.02

0.01

0.02

0.02

0.00

0.00

TFD

0.03

0.03

0.03

0.03

0.02

0.02

TSD

0.01

0.00

0.00

0.00

0.00

0.00

SHGC

0.12

0.11

U-Factor*

1.89

1.89

0.10 1.46

0.09

0.05

0.05

1.27

0.80

0.58

U-FactorEdge

2.10

2.10

1.82

1.40

1.03

0.88

LI

0.04

0.04

0.04

0.04

0.03

0.04

VOI

0.94

0.94

0.93

0.94

0.94

0.94

*The calculation of the U-factors assumes that the wind can penetrate through the screen perforations to the air space between the screen and the window.

39

  Figure 10 Exterior screen shadings in a closed position. Figure 11 shows the profile of the threshold indoor relative humidity for moisture condensation on the interior surfaces of windows with exterior screen shadings. Similarly to exterior rollshutters, exterior screens may significantly reduce the risk of moisture condensation on the interior surfaces of windows. To avoid potential moisture condensation on the interior surfaces of both conventional and high performance windows, the indoor relative humidity should be lower than 35% in cold outdoor weather conditions (outdoor temperatures higher than -30oC). Humidifiers or any moisture generation sources should be carefully monitored during winter to avoid excessive moisture condensation on windows. 100

windows with exterior screens

90

Relative Humidity (%)

80 70 60 50 40 30 20 DBLC: center

TPLC: center

DLCE: center

TCSE: center

TCME: center

DBLC: edge

TPLC: edge

DLCE: edge

TCSE: edge

TCME: edge

10 0 -5

-10

-15

-20

-25

-30

-35

-40

Outdoor Temperature ( C) O

Figure 11 Moisture condensation on the interior surfaces of windows with exterior screen shadings when the indoor temperature is set at 21oC.

40

 

ANNUAL HEATING AND COOLING ENERGY USE AND COST Annual energy use and cost are among the main criteria used to select a house fenestration system. Energy-efficient fenestration systems contribute to improve the quality of the indoor environment (by improving the thermal comfort conditions near windows, reducing the risk of moisture condensation on the window interior surfaces, etc.). They also protect the outdoor environment by reducing the environmental footprint of houses and the nation’s dependency on non-renewable energy sources. The energy cost of fenestration systems may help homeowners to save on the cost to operate their dwellings. The energy cost is also the main factor to determine the payback return period of a technology. In this study, the effect of various combinations of conventional and high performance windows and shading device types on the house annual energy use and cost are analyzed for four Canadian sites. Appendix A provides more details on the computer simulation methodology. Table 8 summarizes the regional fuel types and cost used for a house heating and cooling. Two types of house construction technologies were considered: old constructions (year 1980) and current constructions (based on the R-2000 standard). Houses based on old construction practices usually use conventional double clear windows, and those based on current construction practices generally use double clear low-e windows. The cases where old constructions houses were combined with high performance windows, or the cases where current constructions houses were combined with conventional windows represent examples of renovated houses, regardless of whether only the windows or other envelope elements were retrofitted. House cases where current constructions were combined with super windows (such as triple clear super or reflective low-e windows) represent cases of future lowenergy or net-zero energy houses. Net-zero energy houses produce as much energy (using, for example, photovoltaics) as they use on a yearly basis. Table 8

Types and cost of fuels used for house heating and cooling. Data for heating fuel were taken from StatsCan (2008) and data for electricity cost were taken from Hydro Quebec (2008). Ottawa (ON)

Montreal (QC)

Winnipeg (MB)

Halifax (NS)

Fuel type for heating

Natural gas

Electricity

Natural gas

Oil

Fuel cost ($/kWh)

0.045

0.077

0.035

0.103

Electricity cost ($/kWh)

0.11

0.077

0.074

0.123

41

UN-SHADED WINDOWS RESULTS FOR OTTAWA Figure 12 shows the annual heating and cooling energy use for houses with un-shaded windows located in Ottawa, Ontario. As Ottawa is situated in a heating-dominated climate region, the annual cooling energy use represents only around 5% of the annual heating energy use for both house construction types. The old house types use about 94% more heating energy than the current house types. Windows with high solar heat gains and low U-factors are the best candidates for all types of houses. Houses with low solar heat gain windows such as double green windows have the highest heating energy use (6% more when compared with double clear windows), but with significantly lower cooling energy use (27% less). The effect of window type is more significant with current house types than with old house types. Renovating the double clear windows of an old house type with double clear low-e windows will result in annual heating energy savings of about 7%. This, however, will generate a slight increase in the annual cooling energy use of 4%. Triple clear super low-e windows are effective in reducing the cooling energy use of old houses by up to 33%, but they do not seem to be an attractive renovation option when compared with double clear low-e windows, as they slightly reduce the house heating energy use by only 4%. Furthermore, renovating the windows of an old house type with triple clear reflective (with heat mirror HM88) low-e windows may further reduce the heating energy use by 11%. This latter window type is also an attractive option to renovate the double clear low-e windows of current house types in order to achieve the goals of future low-energy or net-zero energy houses (heating energy savings in the order of 5%). Triple clear super low-e windows seem to increase the heating energy use of the current house types by 5%, but they have the lowest cooling energy use (38% less). Figure 13 shows the annual heating and the total (heating and cooling) energy cost. The total cost for heating and cooling energy to operate an old house in Ottawa is around $1878, whereas the current house types with double clear low-e windows cost around $1014. The cooling energy cost represents only about 10% and 15% of the total energy cost of the old and current house types, respectively. Houses with double green windows have the highest energy cost and, therefore, they are not suitable for window renovations in Ottawa. Renovating the double clear windows of old houses with double clear low-e windows results in total energy cost savings of about $115 (or 6%). Using triple clear super or reflective low-e windows for renovating old houses will result in further significant cost savings ranging from $136 to $211 (or 7% to 11%). Renovating the double clear low-e windows of current house types with triple clear super or reflective low-e windows results, however, in lower total energy cost savings ranging from $15 to $74 (or 1% to 7%).

42

45,000

Energy Consumption (kWh)

40,000

Heating (R-2000)

Heating (Old)

Cooling (R-2000)

Cooling (Old)

35,000

30,000

25,000

20,000

15,000

10,000

5,000

0 Double clear

Double green

Triple clear

Double lowE

Triple super lowE

Triple HM lowE

  Figure 12 Annual heating and cooling energy use of old and R-2000 house models with un-shaded windows (Ottawa, ON). $2,500

Total (R-2000)

Heating (R-2000)

Total (Old)

Heating (Old)

Cost

$2,000

$1,500

$1,000

$500

$0 Double clear

Double green

Triple clear

Double lowE

Triple super lowE

Triple HM lowE

  Figure 13 Annual total and heating energy cost of old and R-2000 house models with un-shaded windows (Ottawa, ON).

43

RESULTS FOR MONTREAL Figure 14 shows the annual heating and cooling energy use houses with un-shaded windows located in Montreal, Quebec. Montreal’s climate is similar to the heating-dominated climate of Ottawa. Old houses in Montreal consume about 64% more heating energy than current house types. Old houses use a high efficiency heating source (electric furnaces with 100% efficiency) and, therefore, their energy consumption is about 7% lower than that of similar houses in Ottawa (which use natural gas furnaces with a medium efficiency of 78%). However, the same conclusions outlined above for Ottawa also apply to Montreal with regard to the effect of window types on the house energy use. Figure 15 shows the annual heating and total energy costs. The total cost for heating and cooling energy to operate old construction houses in Montreal is around $2736, and that of current house types with double clear low-e windows is around $1678 (or 61% less). The annual cooling energy cost represents about 5% of the total annual energy cost for both types of houses. Houses with double green windows have the highest total energy cost (4% to 7% more compared to double clear windows) and, therefore, they are not suitable for house window renovations. Renovating the double clear windows of old houses with double clear low-e windows results in total energy cost savings of about $151 (or 5%). Triple clear super low-e windows are not suitable for house renovation compared to double clear low-e windows as they do not reduce the total annual energy cost. Triple clear reflective low-e windows seem, however, an attractive renovation option for both house types, providing annual total cost savings ranging from $257 (old house types) to $114 (current house types). 45,000

Energy Consumption (kWh)

40,000

Heating (R-2000)

Heating (Old)

Cooling (R-2000)

Cooling (Old)

35,000

30,000

25,000

20,000

15,000

10,000

5,000

0 Double clear

Double green

Triple clear

Double lowE

Triple super lowE

Triple HM lowE

  Figure 14 Annual heating and cooling energy use of old and R-2000 house models with un-shaded windows (Montreal, QC).

44

$3,500

Total (R-2000)

Heating (R-2000)

Total (Old)

Heating (Old)

$3,000

Cost

$2,500

$2,000

$1,500

$1,000

$500

$0 Double clear

Double green

Triple clear

Double lowE

Triple super lowE

Triple HM lowE

  Figure 15 Annual total and heating energy cost of old and R-2000 house models with un-shaded windows (Montreal, QC).

RESULTS FOR WINNIPEG Figure 16 shows the annual heating and cooling energy use for houses with un-shaded windows located in Winnipeg, Manitoba. Winnipeg’s climate is colder than that of Ottawa, and the annual heating energy use is 6% (for old houses) to 37% (for current houses) higher than that of similar houses located in Ottawa. The annual cooling energy use in Winnipeg represents around 5% of the annual heating energy use of both house types. Old houses consume about 52% more heating energy than current house types. Windows with high solar heat gains and low U-factors are again the best candidates for all types of houses. Houses with low solar heat gain windows such as double green windows have the highest heating energy use (6% more when compared with double clear windows), but with significantly lower cooling energy use (25% to 30% less). Renovating the double clear windows of old houses with double clear low-e windows will result in annual heating energy savings around 8%, but with a slight increase in the annual cooling energy use of 4%. Triple clear super low-e windows are effective in reducing the annual cooling energy use of both house types by 34% to 38%, but they are not an attractive renovation option when compared with double clear low-e windows. Triple clear reflective low-e windows, on the other hand, seem to be a better renovation option for both house types with annual heating energy savings ranging from 5% (current houses) to 13% (old houses). Figure 17 shows the annual heating and total energy costs. The annual total cost for heating and cooling energy to operate old construction houses with double clear windows in Winnipeg is around $1523, and that of current house types with double clear low-e windows is around $1012 (or 34% less). The cooling energy cost represents about 8% of the total energy cost for both house types. Houses with double green windows have the highest total energy cost (3% more compared to double clear windows) and, therefore, they are not suitable for house window renovations. Renovating the double clear windows of

45

old houses with double clear low-e windows results in total annual energy cost savings of about $105 (or 7%). Triple clear super low-e windows are not a suitable option for house renovations compared to the double clear low-e windows as they do not significantly reduce the total annual energy cost. Triple clear reflective low-e windows seem, however, an attractive renovation option for both types of houses, with cost savings ranging from $198 (old house types) to $69 (current house types).

45,000

Energy Consumption (kWh)

40,000

Heating (R-2000)

Heating (Old)

Cooling (R-2000)

Cooling (Old)

35,000

30,000

25,000

20,000

15,000

10,000

5,000

0 Double clear

Double green

Triple clear

Double lowE

Triple super lowE

Triple HM lowE

  Figure 16 Annual heating and cooling energy use of old and R-2000 house models with un-shaded windows (Winnipeg, MB).

46

$2,000

Total (R-2000)

Heating (R-2000)

Total (Old)

Heating (Old)

Cost

$1,500

$1,000

$500

$0 Double clear

Double green

Triple clear

Double lowE

Triple super lowE

Triple HM lowE

  Figure 17 Annual total and heating energy cost of old and R-2000 house models with un-shaded windows (Winnipeg, MB).

RESULTS FOR HALIFAX Figure 18 shows the annual heating and cooling energy use for both house types with un-shaded windows located in Halifax, Nova Scotia. Halifax’s climate is slightly milder than that in Ottawa, but houses in Halifax use less efficient oil furnaces for heating. The cooling energy use in Halifax represents 3% to 5% of the heating energy use for both house types. Old houses use about 70% more heating energy than current house types. Double green windows have the highest heating energy use (6% more than double clear windows), but with significantly lower cooling energy use (33% less). Renovating the double clear windows of old house types with double clear low-e windows will result in heating energy savings around 7%, but with a slight increase in the cooling energy use of 5%. Triple clear super low-e windows are effective in reducing the cooling energy use of both house types by 38%, but are not effective in reducing the house heating energy use when compared with double clear low-e windows. Triple clear reflective low-e windows, on the other hand, seem to be an attractive renovation option for both house types with heating energy savings ranging from 3% (current houses) to 10% (old houses). Figure 19 shows the annual heating and total energy costs. The total cost for heating and cooling energy to run old house types with double clear windows in Halifax is around $3837, and that of current house types with double clear low-e windows is around $2252 (or 41% less). The cooling energy cost represents about 3% to 5% of the total annual energy cost. Houses with double green windows have the highest total energy cost (5% more than double clear windows) and, therefore, they are not suitable for house window renovations. Renovating the double clear windows of old houses with double clear low-e windows results in total energy cost savings of about $236 (or 6%). Triple clear super low-e windows don’t seem to be an attractive renovation option compared with double clear low-e windows as they do not significantly reduce the total annual energy cost. Triple clear reflective low-e windows seem,

47

however, an attractive renovation option for both house types with cost savings ranging from $389 (old house types) to $82 (current house types).

45,000

Energy Consumption (kWh)

40,000

Heating (R-2000)

Heating (Old)

Cooling (R-2000)

Cooling (Old)

35,000

30,000

25,000

20,000

15,000

10,000

5,000

0 Double clear

Double green

Triple clear

Double lowE

Triple super lowE

Triple HM lowE

  Figure 18 Annual heating and cooling energy use of old and R-2000 house models with un-shaded windows (Halifax, NS).

48

$5,000 $4,500

Total (R-2000)

Heating (R-2000)

Total (Old)

Heating (Old)

$4,000

Cost

$3,500 $3,000 $2,500 $2,000 $1,500 $1,000 $500 $0 Double clear

Double green

Triple clear

Double lowE

Triple super lowE

Triple HM lowE

  Figure 19 Annual total and heating energy cost of old and R-2000 house models with un-shaded windows (Halifax, NS).

WINDOWS WITH TYPICAL INTERIOR BLINDS Typical interior blinds (with grey coloured aluminium slats) are medium solar-absorptive shading devices (solar absorptance of slats = 42%). The house energy use is a function of the blinds operational schedule. In this study, based on inputs from a household survey (Veitch et al., 2009), the blinds were assumed to be operated as follows: In the winter, all blinds are open during daytime (blinds down with slats in a horizontal position) and closed during night-time (slats tightly squeezed); In the summer, all blinds of the south, east and west-facing windows are closed day and night. The operation of the northfacing window blinds follow the winter blind schedule (see more details in Appendix A).

RESULTS FOR OTTAWA Figure 20 shows the annual heating and cooling energy use for Ottawa when the house windows are covered by typical interior blinds. When compared with un-shaded windows, typical interior blinds do not have a significant impact on the heating energy use of both house types. However, the blinds reduced the cooling energy use by up to 12%. Figure 21 shows the annual heating and total energy costs. When compared with un-shaded windows, typical interior blinds have very little total energy cost savings for both house types (up to 3%), mainly due to the savings in cooling energy use.

49

45,000

Energy Consumption (kWh)

40,000

Heating (R-2000)

Heating (Old)

Cooling (R-2000)

Cooling (Old)

35,000

30,000

25,000

20,000

15,000

10,000

5,000

0 Double clear

Double green

Triple clear

Double lowE

Triple super lowE

Triple HM lowE

  Figure 20 Annual heating and cooling energy use of old and R-2000 house models with typical interior window blinds (Ottawa, ON). $2,500

Total (R-2000)

Heating (R-2000)

Total (Old)

Heating (Old)

Cost

$2,000

$1,500

$1,000

$500

$0 Double clear

Double green

Triple clear

Double lowE

Triple super lowE

Triple HM lowE

  Figure 21 Annual total and heating energy cost of old and R-2000 house models with typical interior window blinds (Ottawa, ON).

50

RESULTS FOR MONTREAL Figures 22 and 23 show the annual heating and cooling energy use and cost for Montreal. When compared with un-shaded windows, typical interior blinds do not have a significant impact on the heating energy use and the total energy cost of both types of houses. However, the blinds reduced the cooling energy use by up to 11%.

45,000

Energy Consumption (kWh)

40,000

Heating (R-2000)

Heating (Old)

Cooling (R-2000)

Cooling (Old)

35,000

30,000

25,000

20,000

15,000

10,000

5,000

0 Double clear

Double green

Triple clear

Double lowE

Triple super lowE

Triple HM lowE

  Figure 22 Annual heating and cooling energy use of old and R-2000 house models with typical interior window blinds (Montreal, QC).

51

$3,500

$3,000

Total (R-2000)

Heating (R-2000)

Total (Old)

Heating (Old)

Cost

$2,500

$2,000

$1,500

$1,000

$500

$0 Double clear

Double green

Triple clear

Double lowE

Triple super lowE

Triple HM lowE

  Figure 23 Annual total and heating energy cost of old and R-2000 house models with typical interior window blinds (Montreal, QC).

RESULTS FOR WINNIPEG Figures 24 and 25 show the annual heating and cooling energy use and cost for Winnipeg. The results are similar to those obtained for Ottawa.

52

45,000

Energy Consumption (kWh)

40,000

Heating (R-2000)

Heating (Old)

Cooling (R-2000)

Cooling (Old)

35,000

30,000

25,000

20,000

15,000

10,000

5,000

0 Double clear

Double green

Triple clear

Double lowE

Triple super lowE

Triple HM lowE

  Figure 24 Annual heating and cooling energy use of old and R-2000 house models with typical interior window blinds (Winnipeg, MB). $2,000

Total (R-2000)

Heating (R-2000)

Total (Old)

Heating (Old)

Cost

$1,500

$1,000

$500

$0 Double clear

Double green

Triple clear

Double lowE

Triple super lowE

Triple HM lowE

  Figure 25 Annual total and heating energy cost of old and R-2000 house models with typical interior window blinds (Winnipeg, MB).

53

RESULTS FOR HALIFAX Figures 26 and 27 show the annual heating and cooling energy use and cost for Halifax. When compared with un-shaded windows, typical interior blinds do not have a significant impact on the heating energy use and the total energy cost of both types of houses. However, the blinds reduced the cooling energy use by up to 15%.

45,000

Energy Consumption (kWh)

40,000

Heating (R-2000)

Heating (Old)

Cooling (R-2000)

Cooling (Old)

35,000

30,000

25,000

20,000

15,000

10,000

5,000

0 Double clear

Double green

Triple clear

Double lowE

Triple super lowE

Triple HM lowE

  Figure 26 Annual heating and cooling energy use of old and R-2000 house models with typical interior window blinds (Halifax, NS).

54

$5,000 $4,500

Total (R-2000)

Heating (R-2000)

Total (Old)

Heating (Old)

$4,000

Cost

$3,500 $3,000 $2,500 $2,000 $1,500 $1,000 $500 $0 Double clear

Double green

Triple clear

Double lowE

Triple super lowE

Triple HM lowE

  Figure 27 Annual total and heating energy cost of old and R-2000 house models with typical interior window blinds (Halifax, NS).

WINDOWS WITH INTERIOR REFLECTIVE BLINDS RESULTS FOR OTTAWA Figures 28 and 29 show the annual heating and cooling energy use and cost for Ottawa when the house windows are covered by interior reflective blinds. When compared with typical interior blinds, the reflective blinds increased the heating energy use by up to 3% for both house types, but reduced the cooling energy use by 13%. As a result, the reflective blinds have very little effect on the total energy cost (less than 1%).

55

45,000

Heating (R-2000)

Heating (Old)

Cooling (R-2000)

Cooling (Old)

Energy Consumption (kWh)

40,000

35,000

30,000

25,000

20,000

15,000

10,000

5,000

0 Double clear

Double green

Triple clear

Double lowE

Triple super lowE

Triple HM lowE

  Figure 28 Annual heating and cooling energy use of old and R-2000 house models with interior reflective window blinds (Ottawa, ON). $2,500

Total (R-2000)

Heating (R-2000)

Total (Old)

Heating (Old)

Cost

$2,000

$1,500

$1,000

$500

$0 Double clear

Double green

Triple clear

Double lowE

Triple super lowE

Triple HM lowE

  Figure 29 Annual total and heating energy cost of old and R-2000 house models with interior reflective window blinds (Ottawa, ON).

56

RESULTS FOR MONTREAL Figures 30 and 31 show the annual heating and cooling energy use and cost for Montreal when the house windows are covered by interior reflective blinds. The results are similar to those obtained for Ottawa.

45,000

Heating (R-2000)

Heating (Old)

Cooling (R-2000)

Cooling (Old)

Energy Consumption (kWh)

40,000

35,000

30,000

25,000

20,000

15,000

10,000

5,000

0 Double clear

Double green

Triple clear

Double lowE

Triple super lowE

Triple HM lowE

  Figure 30 Annual heating and cooling energy use of old and R-2000 house models with interior reflective window blinds (Montreal, QC).

57

$3,500

$3,000

Total (R-2000)

Heating (R-2000)

Total (Old)

Heating (Old)

Cost

$2,500

$2,000

$1,500

$1,000

$500

$0 Double clear

Double green

Triple clear

Double lowE

Triple super lowE

Triple HM lowE

  Figure 31 Annual total and heating energy cost of old and R-2000 house models with interior reflective window blinds (Montreal, QC).

RESULTS FOR WINNIPEG Figures 32 and 33 show the annual heating and cooling energy use and cost for Winnipeg when the house windows are covered by interior reflective blinds. The results are similar to those obtained for Ottawa. When compared with typical interior blinds, the reflective blinds increased the heating energy use by up to 3% for both house types, but reduced the cooling energy use by 13%. As a result, the reflective blinds increased the total energy cost by only 2%.

58

45,000

Energy Consumption (kWh)

40,000

Heating (R-2000)

Heating (Old)

Cooling (R-2000)

Cooling (Old)

35,000

30,000

25,000

20,000

15,000

10,000

5,000

0 Double clear

Double green

Triple clear

Double lowE

Triple super lowE

Triple HM lowE

  Figure 32 Annual heating and cooling energy use of old and R-2000 house models with interior reflective window blinds (Winnipeg, MB). $2,000

Total (R-2000)

Heating (R-2000)

Total (Old)

Heating (Old)

Cost

$1,500

$1,000

$500

$0 Double clear

Double green

Triple clear

Double lowE

Triple super lowE

Triple HM lowE

  Figure 33 Annual total and heating energy cost of old and R-2000 house models with interior reflective window blinds (Winnipeg, MB).

59

RESULTS FOR HALIFAX Figures 34 and 35 show the annual heating and cooling energy use and cost for Halifax when the house windows are covered by interior reflective blinds. The results are similar to those obtained for Ottawa. When compared with typical interior blinds, the reflective blinds increased the heating energy use by 2% (old houses) to 4% (current houses). However, the blinds reduced the cooling energy use by 13% (current houses) to 18% (old houses). As a result, the reflective blinds increased the total energy cost by 1% (old houses) to 3% (current houses).

45,000

Heating (R-2000)

Heating (Old)

Cooling (R-2000)

Cooling (Old)

Energy Consumption (kWh)

40,000

35,000

30,000

25,000

20,000

15,000

10,000

5,000

0 Double clear

Double green

Triple clear

Double lowE

Triple super lowE

Triple HM lowE

  Figure 34 Annual heating and cooling energy use of old and R-2000 house models with interior reflective window blinds (Halifax, NS).

60

$5,000 $4,500

Total (R-2000)

Heating (R-2000)

Total (Old)

Heating (Old)

$4,000

Cost

$3,500 $3,000 $2,500 $2,000 $1,500 $1,000 $500 $0 Double clear

Double green

Triple clear

Double lowE

Triple super lowE

Triple HM lowE

  Figure 35 Annual total and heating energy cost of old and R-2000 house models with interior reflective window blinds (Halifax, NS).

WINDOWS WITH INTERIOR REFLECTIVE SCREENS The operation of reflective screen shadings is quite different from that of reflective blinds. When the screen is in an open position, the whole window surface area is uncovered, thus admitting more solar heat gains indoors compared to reflective blinds with slats horizontal. Furthermore, the reflective side of the screen shades has a low emissivity coating (emissivity = 0.16; see Table 19), which may contribute to reduce the radiant heat losses through windows. Other commercial screen shadings do not have such a low-emissivity feature.

RESULTS FOR OTTAWA Figures 36 and 37 show the annual heating and cooling energy use and cost for Ottawa when the house windows are covered by interior reflective screens. When compared with typical interior blinds, the reflective screens reduced the cooling energy use by up to 21%, and the heating energy use by up to 4% for both house types. As a result, the total energy cost savings may reach up to $100 (or 5%) for old house types and up to $41 (or 4%) for current house types.

61

45,000

Heating (R-2000)

Heating (Old)

Cooling (R-2000)

Cooling (Old)

Energy Consumption (kWh)

40,000

35,000

30,000

25,000

20,000

15,000

10,000

5,000

0 Double clear

Double green

Triple clear

Double lowE

Triple super lowE

Triple HM lowE

  Figure 36 Annual heating and cooling energy use of old and R-2000 house models with interior reflective window screens (Ottawa, ON). $2,500

Total (R-2000)

Heating (R-2000)

Total (Old)

Heating (Old)

Cost

$2,000

$1,500

$1,000

$500

$0 Double clear

Double green

Triple clear

Double lowE

Triple super lowE

Triple HM lowE

  Figure 37 Annual total and heating energy cost of old and R-2000 house models with interior reflective window screens (Ottawa, ON).

62

RESULTS FOR MONTREAL Figures 38 and 39 show the annual heating and cooling energy use and cost for Montreal when the house windows are covered by interior reflective screens. The results are similar to those obtained for Ottawa. When compared with typical interior blinds, the reflective screens reduced the cooling energy use by up to 21% for both types of houses, and the heating energy use by 2% (current houses) to 4% (old houses). As a result, the total energy cost savings may reach up to $119 (or 4%) for old house types and up to $56 (or 3%) for current house types.

45,000

Heating (R-2000)

Heating (Old)

Cooling (R-2000)

Cooling (Old)

Energy Consumption (kWh)

40,000

35,000

30,000

25,000

20,000

15,000

10,000

5,000

0 Double clear

Double green

Triple clear

Double lowE

Triple super lowE

Triple HM lowE

  Figure 38 Annual heating and cooling energy use of old and R-2000 house models with interior reflective window screens (Montreal, QC).

63

$3,500

$3,000

Total (R-2000)

Heating (R-2000)

Total (Old)

Heating (Old)

Cost

$2,500

$2,000

$1,500

$1,000

$500

$0 Double clear

Double green

Triple clear

Double lowE

Triple super lowE

Triple HM lowE

  Figure 39 Annual total and heating energy cost of old and R-2000 house models with interior reflective window screens (Montreal, QC).

RESULTS FOR WINNIPEG Figures 40 and 41 show the annual heating and cooling energy use and cost for Winnipeg when the house windows are covered by interior reflective screens. The results are similar to those obtained for Ottawa. When compared with typical interior blinds, the reflective screens reduced the cooling energy use by up to 23% for both types of houses, and the heating energy use by 2% (current houses) to 3% (old houses). As a result, the total energy cost savings may reach up to $68 (or 5%) for old house types and up to $35 (or 3%) for current house types.

64

45,000

Heating (R-2000)

Heating (Old)

Cooling (R-2000)

Cooling (Old)

Energy Consumption (kWh)

40,000

35,000

30,000

25,000

20,000

15,000

10,000

5,000

0 Double clear

Double green

Triple clear

Double lowE

Triple super lowE

Triple HM lowE

  Figure 40 Annual heating and cooling energy use of old and R-2000 house models with interior reflective window screens (Winnipeg, MB). $2,000

Total (R-2000)

Heating (R-2000)

Total (Old)

Heating (Old)

Cost

$1,500

$1,000

$500

$0 Double clear

Double green

Triple clear

Double lowE

Triple super lowE

Triple HM lowE

  Figure 41 Annual total and heating energy cost of old and R-2000 house models with interior reflective window screens (Winnipeg, MB).

65

RESULTS FOR HALIFAX Figures 42 and 43 show the annual heating and cooling energy use and cost for Halifax when the house windows are covered by interior reflective screens. The results are similar to those obtained for Ottawa. When compared with typical interior blinds, the reflective screens reduced the cooling energy use by up to 27% for both types of houses, and the heating energy use by up to 3% for old houses only. As a result, the total energy cost savings may reach up to $132 (or 4%) for old house types and up to $38 (or 2%) for current house types.

45,000

Heating (R-2000)

Heating (Old)

Cooling (R-2000)

Cooling (Old)

Energy Consumption (kWh)

40,000

35,000

30,000

25,000

20,000

15,000

10,000

5,000

0 Double clear

Double green

Triple clear

Double lowE

Triple super lowE

Triple HM lowE

Figure 42 Annual heating and cooling energy use of old and R-2000 house models with interior reflective window screens (Halifax, NS).

66

$5,000 $4,500

Total (R-2000)

Heating (R-2000)

Total (Old)

Heating (Old)

$4,000

Cost

$3,500 $3,000 $2,500 $2,000 $1,500 $1,000 $500 $0 Double clear

Double green

Triple clear

Double lowE

Triple super lowE

Triple HM lowE

  Figure 43 Annual total and heating energy cost of old and R-2000 house models with interior reflective window screens (Halifax, NS).

WINDOWS WITH BETWEEN-PANE REFLECTIVE BLINDS RESULTS FOR OTTAWA Figures 44 and 45 show the annual heating and cooling energy use and cost for Ottawa when metallic reflective blinds are integrated in the window gas space cavities. The between-pane metallic blinds are not suitable for heating-dominated climates, particularly when integrated in high performance windows. When compared with typical interior blinds, the metallic reflective blinds effectively reduced the cooling energy use by up to 45% for old house types and up to 57% for current house types. However, they increased the heating energy use by up to 5% for old houses, and up to 15% for current houses. As a result, between-pane reflective blinds may increase the total energy cost by up to $57 (or 6%), particularly for current houses with double clear low-e windows. However, the effect on the total energy cost was not significant when the blinds were combined with conventional double or triple clear windows of old houses. If such metallic blinds have to be integrated in windows for one reason or another, they should be integrated in triple pane windows and drawn up when -open (instead of covering the window area with slats horizontal) to reduce the effect of thermal bridges and to increase the solar heat gains.

67

45,000

Energy Consumption (kWh)

40,000

Heating (R-2000)

Heating (Old)

Cooling (R-2000)

Cooling (Old)

35,000

30,000

25,000

20,000

15,000

10,000

5,000

0 Double clear

Double green

Triple clear

Double lowE

Triple super lowE

Triple HM lowE

  Figure 44 Annual heating and cooling energy use of old and R-2000 house models with between-pane reflective window blinds (Ottawa, ON). $2,500

Total (R-2000)

Heating (R-2000)

Total (Old)

Heating (Old)

Cost

$2,000

$1,500

$1,000

$500

$0 Double clear

Double green

Triple clear

Double lowE

Triple super lowE

Triple HM lowE

  Figure 45 Annual total and heating energy cost of old and R-2000 house models with between-pane reflective window blinds (Ottawa, ON).

68

RESULTS FOR MONTREAL Figures 46 and 47 show the annual heating and cooling energy use and cost for Montreal when metallic reflective blinds are integrated in the window gas space cavities. The results are similar to those obtained for Ottawa. When compared with typical interior blinds, the between-pane metallic reflective blinds effectively reduced the cooling energy use by up to 38% for old house types and up to 59% for current house types. However, they also increased the heating energy use by up to 4% for old houses, and up to 13% for current houses. As a result, between-pane metallic blinds may increase the total energy cost by up to $158 (or 9%) for the current houses and up to $44 (or 2%) for old houses. 45,000

Energy Consumption (kWh)

40,000

Heating (R-2000)

Heating (Old)

Cooling (R-2000)

Cooling (Old)

35,000

30,000

25,000

20,000

15,000

10,000

5,000

0 Double clear

Double green

Triple clear

Double lowE

Triple super lowE

Triple HM lowE

  Figure 46 Annual heating and cooling energy use of old and R-2000 house models with between-pane reflective window blinds (Montreal, QC).

69

$3,500

$3,000

Total (R-2000)

Heating (R-2000)

Total (Old)

Heating (Old)

Cost

$2,500

$2,000

$1,500

$1,000

$500

$0 Double clear

Double green

Triple clear

Double lowE

Triple super lowE

Triple HM lowE

  Figure 47 Annual total and heating energy cost of old and R-2000 house models with between-pane reflective window blinds (Montreal, QC).

RESULTS FOR WINNIPEG Figures 48 and 49 show the annual heating and cooling energy use and cost for Winnipeg when metallic reflective blinds are integrated in windows. The results are similar to those obtained for Ottawa. When compared with the typical interior blinds, the between-pane reflective blinds effectively reduced the cooling energy use by up to 46% for old house types and up to 58% for current house types. However, they have also increased the heating energy use by up to 5% for the old houses, and up to 12% for current houses. As a result, between-pane metallic reflective blinds may increase the total energy cost by up to $65 (or 7%) for current houses and up to $21 (or 1%) for old houses.

70

45,000

Energy Consumption (kWh)

40,000

Heating (R-2000)

Heating (Old)

Cooling (R-2000)

Cooling (Old)

35,000

30,000

25,000

20,000

15,000

10,000

5,000

0 Double clear

Double green

Triple clear

Double lowE

Triple super lowE

Triple HM lowE

Figure 48 Annual heating and cooling energy use of old and R-2000 house models with between-pane reflective window blinds (Winnipeg, MB). $2,000

Total (R-2000)

Heating (R-2000)

Total (Old)

Heating (Old)

Cost

$1,500

$1,000

$500

$0 Double clear

Double green

Triple clear

Double lowE

Triple super lowE

Triple HM lowE

  Figure 49 Annual total and heating energy cost of old and R-2000 house models with between-pane reflective window blinds (Winnipeg, MB).

71

RESULTS FOR HALIFAX Figures 50 and 51 show the annual heating and cooling energy use and cost for Halifax when metallic reflective blinds are integrated in windows. The blinds are again not suitable for milder heatingdominated climates such as that in Halifax when they are integrated in conventional or high performance windows. When compared with typical interior blinds, the between-pane blinds effectively reduced the cooling energy use by up to 56% for the old houses, and up to 70% for current houses. However, they also increased the heating energy use by up to 4% for old houses, and up to 16% for current houses. As a result, between-pane blinds may increase the total energy cost by up to $260 (or 12%) for current houses and up to $95 (or 3%) for the old houses. 45,000

Energy Consumption (kWh)

40,000

Heating (R-2000)

Heating (Old)

Cooling (R-2000)

Cooling (Old)

35,000

30,000

25,000

20,000

15,000

10,000

5,000

0 Double clear

Double green

Triple clear

Double lowE

Triple super lowE

Triple HM lowE

  Figure 50 Annual heating and cooling energy use of old and R-2000 house models with between-pane reflective window blinds (Halifax, NS).

72

$5,000 $4,500

Total (R-2000)

Heating (R-2000)

Total (Old)

Heating (Old)

$4,000

Cost

$3,500 $3,000 $2,500 $2,000 $1,500 $1,000 $500 $0 Double clear

Double green

Triple clear

Double lowE

Triple super lowE

Triple HM lowE

  Figure 51 Annual total and heating energy cost of old and R-2000 house models with between-pane reflective window blinds (Halifax, NS).

WINDOWS WITH EXTERIOR ROLLSHUTTERS The results presented below apply to exterior insulating rollshutters where the air space between the window and the shutter is sealed when the shutter is in a closed position (for example using side rails and a bottom sill with rubber caskets). The shutters operational schedules used in the simulations for winter and summer are identical to those used for the interior screens (see details in Appendix A). When the shutters were considered to be in an open position, the windows were simulated as completely uncovered and admitting maximum daylight and solar heat gains indoors.

RESULTS FOR OTTAWA Figures 52 and 53 show the annual heating and cooling energy use and cost for Ottawa when the house windows are covered by exterior insulating rollshutters. Exterior rollshutters are the most effective shading devices to reduce the house heating and cooling energy use. The effect of rollshutters is more pronounced when they are used with conventional windows than with high performance windows. When compared with typical interior blinds, the rollshutters reduced the heating energy use by 8% for old houses with double clear windows, and by 7% for current house types with double clear low-e windows. However, the effect of rollshutters on the house heating energy use was not significant when they were combined with super windows (centre of glazing U-factor < 1 W/m2oC) such as triple clear reflective low-e windows (centre of glazing U-factor = 0.6 W/m2oC). The effect of rollshutters on the cooling energy use was independent of the window and house construction type. When compared with typical interior blinds, the cooling energy use of houses with rollshutters was lower by 45% to 54%. Consequently, the total annual energy cost savings may range from $208 (or 11%) for old houses to $133 (or 13%) for current houses.

73

It should be noted that the combination of exterior rollshutters with double clear low-e windows in old or current types of houses was the most energy-efficient (lowest energy use) and cost-effective (lowest total energy cost) among the six combinations of window types and rollshutters studied.

45,000

Energy Consumption (kWh)

40,000

Heating (R-2000)

Heating (Old)

Cooling (R-2000)

Cooling (Old)

35,000

30,000

25,000

20,000

15,000

10,000

5,000

0 Double clear

Double green

Triple clear

Double lowE

Triple super lowE

Triple HM lowE

  Figure 52 Annual heating and cooling energy use of old and R-2000 house models with exterior window rollshutters (Ottawa, ON).

74

$2,500

Total (R-2000)

Heating (R-2000)

Total (Old)

Heating (Old)

Cost

$2,000

$1,500

$1,000

$500

$0 Double clear

Double green

Triple clear

Double lowE

Triple super lowE

Triple HM lowE

  Figure 53 Annual total and heating energy cost of old and R-2000 house models with exterior window rollshutters (Ottawa, ON).

RESULTS FOR MONTREAL Figures 54 and 55 show the annual heating and cooling energy use and cost for Montreal when the house windows are covered by rollshutters. The results are similar to those obtained for Ottawa. When compared with typical interior blinds, the rollshutters reduced the heating energy use by 7% for both old and current house types. The effect of rollshutters on the house heating energy use was not significant when they were combined with super windows such as triple clear reflective low-e windows (centre of glazing U-factor = 0.6 W/m2oC). Rollshutters reduced the annual cooling energy use by 40% to 60%. Consequently, the total annual energy cost savings may range from $158 (or 10%) for current houses to $222 (or 8%) for old houses.

75

45,000

Energy Consumption (kWh)

40,000

Heating (R-2000)

Heating (Old)

Cooling (R-2000)

Cooling (Old)

35,000

30,000

25,000

20,000

15,000

10,000

5,000

0 Double clear

Double green

Triple clear

Double lowE

Triple super lowE

Triple HM lowE

  Figure 54 Annual heating and cooling energy use of old and R-2000 house models with exterior window rollshutters (Montreal, QC). $3,500

$3,000

Total (R-2000)

Heating (R-2000)

Total (Old)

Heating (Old)

Cost

$2,500

$2,000

$1,500

$1,000

$500

$0 Double clear

Double green

Triple clear

Double lowE

Triple super lowE

Triple HM lowE

  Figure 55 Annual total and heating energy cost of old and R-2000 house models with exterior window rollshutters (Montreal, QC).

76

RESULTS FOR WINNIPEG Figures 56 and 57 show the annual heating and cooling energy use and cost for Winnipeg when the house windows are covered by exterior insulating rollshutters. The results are similar to those obtained for Ottawa. When compared with typical interior blinds, the rollshutters reduced the heating energy use by 6% to 8% for both old and current house types. The effect of rollshutters on the house heating energy use was not significant when they were combined with super windows such as triple clear reflective low-e windows (centre of glazing U-factor = 0.6 W/m2oC). Rollshutters reduced the annual cooling energy use by 50% to 60%. Consequently, the total annual energy cost savings may range from $106 (or 11%) for current houses to $163 (or 11%) for old houses. 45,000

Energy Consumption (kWh)

40,000

Heating (R-2000)

Heating (Old)

Cooling (R-2000)

Cooling (Old)

35,000

30,000

25,000

20,000

15,000

10,000

5,000

0 Double clear

Double green

Triple clear

Double lowE

Triple super lowE

Triple HM lowE

  Figure 56 Annual heating and cooling energy use of old and R-2000 house models with exterior window rollshutters (Winnipeg, MB).

77

$2,000

Total (R-2000)

Heating (R-2000)

Total (Old)

Heating (Old)

Cost

$1,500

$1,000

$500

$0 Double clear

Double green

Triple clear

Double lowE

Triple super lowE

Triple HM lowE

  Figure 57 Annual total and heating energy cost of old and R-2000 house models with exterior window rollshutters (Winnipeg, MB).

RESULTS FOR HALIFAX Figures 58 and 59 show the annual heating and cooling energy use and cost for Halifax when the house windows are covered by exterior insulating rollshutters. The results are similar to those obtained for Ottawa. When compared with typical interior blinds, rollshutters reduced the heating energy use by 6% to 9% for both old and current house types. The effect of rollshutters on the house heating energy use was not significant when they were used with super windows such as triple clear reflective low-e windows (centre of glazing U-factor = 0.6 W/m2oC). Rollshutters reduced the annual cooling energy use by 57% to 65%. Consequently, the total annual energy cost savings may range from $197 (or 9%) for current houses to $385 (or 10%) for old houses.

78

45,000

Energy Consumption (kWh)

40,000

Heating (R-2000)

Heating (Old)

Cooling (R-2000)

Cooling (Old)

35,000

30,000

25,000

20,000

15,000

10,000

5,000

0 Double clear

Double green

Triple clear

Double lowE

Triple super lowE

Triple HM lowE

  Figure 58 Annual heating and cooling energy use of old and R-2000 house models with exterior window rollshutters (Halifax, NS). $5,000 $4,500

Total (R-2000)

Heating (R-2000)

Total (Old)

Heating (Old)

$4,000

Cost

$3,500 $3,000 $2,500 $2,000 $1,500 $1,000 $500 $0 Double clear

Double green

Triple clear

Double lowE

Triple super lowE

Triple HM lowE

  Figure 59 Annual total and heating energy cost of old and R-2000 house models with exterior window rollshutters (Halifax, NS).

79

WINDOWS WITH EXTERIOR SCREENS The results presented below apply to exterior perforated black screens where the air space between the window and the screen is partially sealed when the screen is in a closed position (sealed at the edges, but the wind can penetrate the screen through the perforations). The screen operational schedules used in the simulations for winter and summer are identical to those used for exterior rollshutters.

RESULTS FOR OTTAWA Figures 60 and 61 show the annual heating and cooling energy use and cost for Ottawa when the house windows are covered by exterior screens. The effect of exterior screens on the house energy use is similar to those of exterior rollshutters, but with lower magnitudes. When compared with typical interior blinds, the exterior screens reduced the heating energy use by 6% for both old houses with double clear windows and current houses with double clear low-e windows. However, the effect of the exterior screens on the house heating energy use was not significant when they were used with super windows such as triple clear reflective low-e windows (centre of glazing U-factor = 0.6 W/m2oC). The exterior screen shades reduced the cooling energy use by 34% and 47% for old and current types of houses, respectively. Consequently, the total annual energy cost savings may range from $110 (or 11%) for current houses to $158 (or 9%) for old houses. Similarly to the exterior rollshutters, the combination of exterior screen shades with double clear low-e windows in both types of houses was the most energy-efficient (lowest total energy use) and costeffective (lowest total energy cost) among the six combinations of window types and exterior screens studied. 45,000

Energy Consumption (kWh)

40,000

Heating (R-2000)

Heating (Old)

Cooling (R-2000)

Cooling (Old)

35,000

30,000

25,000

20,000

15,000

10,000

5,000

0 Double clear

Double green

Triple clear

Double lowE

Triple super lowE

Triple HM lowE

  Figure 60 Annual heating and cooling energy use of old and R-2000 house models with exterior window screens (Ottawa, ON).

80

$2,500

Total (R-2000)

Heating (R-2000)

Total (Old)

Heating (Old)

Cost

$2,000

$1,500

$1,000

$500

$0 Double clear

Double green

Triple clear

Double lowE

Triple super lowE

Triple HM lowE

  Figure 61 Annual total and heating energy cost of old and R-2000 house models with exterior window screens (Ottawa, ON).

RESULTS FOR MONTREAL Figures 62 and 63 show the annual heating and cooling energy use and cost for Montreal when the house windows are covered by exterior screens. The results are similar to those obtained for Ottawa. When compared with typical interior blinds, the exterior screens reduced the heating energy use by 5% for both old houses with double clear windows and current houses with double clear low-e windows. The effect of the exterior screens on the house heating energy use was not significant when they were used with super windows such as triple clear reflective low-e windows (centre of glazing U-factor = 0.6 W/m2oC). The exterior screen shades reduced the cooling energy use by 30% and 50% for old and current types of houses, respectively. Consequently, the total annual energy cost savings may range from $116 (or 7%) for current houses to $175 (or 6%) for old houses.

81

45,000

Energy Consumption (kWh)

40,000

Heating (R-2000)

Heating (Old)

Cooling (R-2000)

Cooling (Old)

35,000

30,000

25,000

20,000

15,000

10,000

5,000

0 Double clear

Double green

Triple clear

Double lowE

Triple super lowE

Triple HM lowE

  Figure 62 Annual heating and cooling energy use of old and R-2000 house models with exterior window screens (Montreal, QC). $3,500

$3,000

Total (R-2000)

Heating (R-2000)

Total (Old)

Heating (Old)

Cost

$2,500

$2,000

$1,500

$1,000

$500

$0 Double clear

Double green

Triple clear

Double lowE

Triple super lowE

Triple HM lowE

  Figure 63 Annual total and heating energy cost of old and R-2000 house models with exterior window screens (Montreal, QC).

82

RESULTS FOR WINNIPEG Figures 64 and 65 show the annual heating and cooling energy use and cost for Winnipeg when the house windows are covered by exterior screens. The results are similar to those obtained for Ottawa. When compared with typical interior blinds, the exterior screens reduced the heating energy use by 6% for both old houses with double clear windows and current houses with double clear low-e windows. The effect of exterior screens on the house heating energy use was not significant when they were used with super windows such as triple clear reflective low-e windows (centre of glazing U-factor = 0.6 W/m2oC). The exterior screen shades reduced the cooling energy use by 37% and 51% for old and current types of houses, respectively. Consequently, the total annual energy cost savings may range from $84 (or 8%) for current houses to $124 (or 8%) for old houses.

45,000

Energy Consumption (kWh)

40,000

Heating (R-2000)

Heating (Old)

Cooling (R-2000)

Cooling (Old)

35,000

30,000

25,000

20,000

15,000

10,000

5,000

0 Double clear

Double green

Triple clear

Double lowE

Triple super lowE

Triple HM lowE

  Figure 64 Annual heating and cooling energy use of old and R-2000 house models with exterior window screens (Winnipeg, MB).

83

$2,000

Total (R-2000)

Heating (R-2000)

Total (Old)

Heating (Old)

Cost

$1,500

$1,000

$500

$0 Double clear

Double green

Triple clear

Double lowE

Triple super lowE

Triple HM lowE

  Figure 65 Annual total and heating energy cost of old and R-2000 house models with exterior window screens (Winnipeg, MB).

RESULTS FOR HALIFAX Figures 66 and 67 show the annual heating and cooling energy use and cost for Halifax when the house windows are covered by exterior screens. The results are similar to those obtained for Ottawa. When compared with typical interior blinds, exterior screens reduced the heating energy use by 4% to 7% for both old houses with double clear windows and current houses with double clear low-e windows. The effect of the exterior screens on the house heating energy use was not significant when they were used with super windows such as triple clear reflective low-e windows (centre of glazing U-factor = 0.6 W/m2oC). The exterior screen shades reduced the cooling energy use by 46% and 57% for old and current types of houses, respectively. Consequently, the total annual energy cost savings may range from $138 (or 6%) for current houses to $299 (or 8%) for old houses.

84

45,000

Energy Consumption (kWh)

40,000

Heating (R-2000)

Heating (Old)

Cooling (R-2000)

Cooling (Old)

35,000

30,000

25,000

20,000

15,000

10,000

5,000

0 Double clear

Double green

Triple clear

Double lowE

Triple super lowE

Triple HM lowE

  Figure 66 Annual heating and cooling energy use of old and R-2000 house models with exterior window screens (Halifax, NS). $5,000 $4,500

Total (R-2000)

Heating (R-2000)

Total (Old)

Heating (Old)

$4,000

Cost

$3,500 $3,000 $2,500 $2,000 $1,500 $1,000 $500 $0 Double clear

Double green

Triple clear

Double lowE

Triple super lowE

Triple HM lowE

  Figure 67 Annual total and heating energy cost of old and R-2000 house models with exterior window screens (Halifax, NS).

85

PEAK COOLING POWER DEMAND The peak cooling power demand may be considered as one of the criteria to select an efficient fenestration system. The peak cooling power demand is defined as the maximum power used by the cooling system (air conditioner and circulation fan) during the hottest day of the cooling season to maintain comfortable conditions indoors. Although in Canada the cooling energy use is significantly lower than the heating energy use, reductions of the peak cooling power demand have many benefits not only for homeowners, but also for the electric utilities and the environment. Efficient fenestration systems that result in lower cooling power demand during on-peak periods benefit electric utilities by allowing them to install and use less peak generation capacity, which is often fossil-fuel based. When demand is low, less expensive sources of electricity are used. When demand is high, more expensive forms of electricity production are called upon, driving prices higher. If a time-of-use electricity rate is in place, homeowners benefit from reduced cooling energy cost. Furthermore, efficient fenestration systems may result in lower sizes of the cooling equipment and additional capital cost savings for homeowners.

ON-PEAK COOLING POWER DEMAND Most Canadian provinces experience their highest demand during winter electricity peaks, but some jurisdictions do experience substantial summer peak electricity demands due to an increased use of air conditioning units, and Ontario’s summer peak is higher than its winter peak. The on-peak period in Ontario occurs from 11 AM to 5 PM (IESO, 2008). Figures 68 and 69 show the typical effect of various shading devices on the cooling power demand (air conditioner and circulation fan) during two sunny and hot summer days (weekend of July 19 and 20) for old houses with conventional double clear windows, and for R-2000 houses with double clear low-e windows located in Ottawa. The average outdoor temperature between 11 AM to 7 PM was 31oC on July 19 and 32oC on July 20. The peak cooling power demand usually occurs between 5 PM and 6 PM due to the additional interior heat gains accumulated in the house by that time of day. Exterior rollshutters are the most effective shading strategy to reduce the peak power demand. Exterior black screens and between-pane reflective blinds have almost similar effects on the cooling power demand (since they both have almost equal low SHGC values; see Tables 5 and 7). The effect of exterior or between-pane shading devices is more significant with R-2000 houses than with old houses, whereas the reverse occurs with interior shading devices. When compared with unshaded windows, typical interior blinds reduced the on-peak cooling power demand by 5% to 12% (9% on average) for old houses with conventional double clear windows, and by 2% to 10% (7% on average) for R-2000 houses with double clear low-e windows. When compared with typical interior blinds in old houses, exterior rollshutters reduced the on-peak (from 11 AM to 5 PM) cooling power demand by 18% to 42% (30% average), followed by between-pane reflective blinds 20% to 33% (27% average); exterior screens 15% to 30% (22% average); interior reflective screens 8% to 19% (13% average); and interior reflective blinds 4% to 11% (7% average). For R-2000 houses, the exterior rollshutters reduced the onpeak cooling power demand by 29% to 48% (39% average), followed by between-pane reflective blinds 30% to 40% (35% average); exterior screens 25% to 41% (33% average); interior reflective screens 10% to 17% (13% average); and interior reflective blinds 6% to 9% (7% average).

86

3500

No shades

Old (1980) houses July 19‐20 (sunny & hot)

Interior typical blinds Interior reflective blinds Interior reflective screens

3000

Mid-pane reflective blinds Exterior screens

Air Conditioner Power (W)

Exterior rollshutters

2500

2000

1500

1000

500

0 0

6

12

18

24

30

36

42

Time (hr.)

Figure 68 Peak cooling power demand during two sunny and hot summer days for old houses with conventional double clear windows in Ottawa (based on a 15-minute time step).

87

48

 

3500 No shades

R‐2000 model houses July 19‐20 (sunny & hot)

Interior typical blinds Interior reflective blinds

3000

Interior reflective screens

Air Conditioner Power (W)

Mid-pane reflective blinds Exterior screens

2500

Exterior rollshutters

2000

1500

1000

500

0 0

6

12

18

24

30

36

42

48

Time (hr.)

Figure 69 Peak cooling power demand during two sunny and hot summer days for R-2000 houses with double clear low-e windows in Ottawa (based on a 15-minute time step).

AIR-CONDITIONER PEAK POWER Selecting the proper size of the cooling system is one of the measures to maximize the energy efficiency of houses. Air-conditioners, which are operated at their nominal (maximum) capacity are more efficient than those with larger sizes, but operated at a lower than nominal capacity. In the following, we show the effect of selected shading devices on the nominal (maximum) power of the cooling system for different Canadian cities.

RESULTS FOR OTTAWA Figure 70 shows the effect of various shading devices on the peak power demand (or maximum capacity) of the cooling system (air-conditioner and circulation fan) for old and R-2000 houses located in Ottawa. Exterior rollshutters are again the most effective shading devices to reduce the maximum capacity of the cooling system. When compared with un-shaded windows of old houses, exterior rollshutters reduced the maximum power demand of the cooling system by 15% to 21%, followed by between-pane reflective blinds 14% to 22%, exterior screens 12% to 19%, interior reflective screens 11% to 15%, interior reflective blinds 10% to 13%, and interior typical (absorptive) blinds 8%. When compared with unshaded windows of R-2000 houses, exterior rollshutters reduced the maximum power demand of the cooling system by 20% to 27%, followed by between-pane reflective blinds- 17% to 27%, exterior screens 88

 

17% to 25%, interior reflective screens 14%, interior reflective blinds 12%, and interior typical (absorptive) blinds 7%. 5,000 No shades (R‐2000) Int. typical blinds (R‐2000) Int. blinds (R‐2000) Int. screens (R‐2000) Mid‐pane blinds (R‐2000) Ext. screens (R‐2000) Ext. rollshutters (R‐2000)

Air‐conditioner peak power (W)

4,000

No shades (Old) Int. typical blinds (Old) Int. blinds (Old) Int. screens (Old) Mid‐pane blinds (Old) Ext. screens (Old) Ext. rollshutters (Old)

3,000

2,000

1,000

0 Double clear

Double green

Triple clear

Double lowE

Triple super lowE Triple HM lowE

  Figure 70 Effect of the shading devices on the peak power demand of an air-conditioner for an old versus an R-2000 house model (Ottawa, ON).

RESULTS FOR MONTREAL Figure 71 shows the effect of various shading devices on the peak power demand of a cooling system for both types of houses located in Montreal. The results are similar to those obtained for Ottawa. When compared with un-shaded windows of old houses, exterior rollshutters reduced the maximum power demand of the cooling system by 16% to 24%, followed by between-pane reflective blinds 15% to 25%, exterior screens 12% to 19%, interior reflective screens 11% to 17%, interior reflective blinds 9% to 14%, and interior typical (absorptive) blinds 8%. When compared with un-shaded windows of R-2000 houses, exterior rollshutters reduced the maximum power demand of the cooling system by 19% to 33%, followed by between-pane reflective blinds 16% to 33%, exterior screens 12% to 28%, interior reflective screens 9% to 22%, interior reflective blinds 11%, and interior typical (absorptive) blinds 5%.

89

5,000 No shades (R‐2000) Int. typical blinds (R‐2000) Int. blinds (R‐2000) Int. screens (R‐2000) Mid‐pane blinds (R‐2000) Ext. screens (R‐2000) Ext. rollshutters (R‐2000)

Air‐conditioner peak power (W)

4,000

No shades (Old) Int. typical blinds (Old) Int. blinds (Old) Int. screens (Old) Mid‐pane blinds (Old) Ext. screens (Old) Ext. rollshutters (Old)

3,000

2,000

1,000

0 Double clear

Double green

Triple clear

Double lowE Triple super lowE Triple HM lowE

  Figure 71 Effect of the shading devices on the peak power demand of an air-conditioner for an old versus an R-2000 house model (Montreal, QC).

RESULTS FOR WINNIPEG Figure 72 shows the effect of various shading devices on the peak power demand of the cooling system for both types of houses located in Winnipeg. The results are similar to those obtained for Ottawa. When compared with un-shaded windows of old houses, exterior rollshutters reduced the maximum power demand of the cooling system by 19% to 28%, followed by between-pane reflective blinds 13% to 27%, exterior screens 16% to 25%, interior reflective screens 8% to 20%, interior reflective blinds 6% to 15%, and interior typical (absorptive) blinds 3% to 11%. When compared with un-shaded windows of R-2000 houses, exterior rollshutters reduced the maximum power demand of the cooling system by 22% to 29%, followed by between-pane reflective blinds 13% to 29%, exterior screens 9% to 21%, interior reflective screens 9% to 21%, interior reflective blinds 6% to 17%, and interior typical (absorptive) blinds 2%.

90

5,000 No shades (R‐2000) Int. typical blinds (R‐2000) Int. blinds (R‐2000) Int. screens (R‐2000) Mid‐pane blinds (R‐2000) Ext. screens (R‐2000) Ext. rollshutters (R‐2000)

Peak  A/C Power (W)

4,000

No shades (Old) Int. typical blinds (Old) Int. blinds (Old) Int. screens (Old) Mid‐pane blinds (Old) Ext. screens (Old) Ext. rollshutters (Old)

3,000

2,000

1,000

0 Double clear

Double green

Triple clear

Double lowE Triple super lowE Triple HM lowE

  Figure 72 Effect of the shading devices on the peak power demand of an air-conditioner for an old and versus an R-2000 house model (Winnipeg, MB).

RESULTS FOR HALIFAX Figure 73 shows the effect of the shading devices on the peak power demand of a cooling system for both types of houses in Halifax. The results are similar to those for Ottawa. When compared with unshaded windows of old houses, exterior rollshutters reduced the maximum power demand of the cooling system by 20% to 29%, followed by between-pane reflective blinds 13% to 31%, exterior screens 16% to 23%, interior reflective screens 8% to 19%, interior reflective blinds 8% to 16%, and interior typical (absorptive) blinds up to 8%. When compared with un-shaded windows of R-2000 houses, exterior rollshutters may reduce the maximum power demand of the cooling system by 23% to 39%, followed by exterior screens 17% to 40%, between-pane reflective blinds 13% to 29%, interior reflective screens 9% to 22%, interior reflective blinds 8% to 19%, and interior typical (absorptive) blinds up to 7%.

91

5,000 No shades (R‐2000) Int. typical blinds (R‐2000) Int. blinds (R‐2000) Int. screens (R‐2000) Mid‐pane blinds (R‐2000) Ext. screens (R‐2000) Ext. rollshutters (R‐2000)

Air‐conditioner peak power (W)

4,000

No shades (Old) Int. typical blinds (Old) Int. blinds (Old) Int. screens (Old) Mid‐pane blinds (Old) Ext. screens (Old) Ext. rollshutters (Old)

3,000

2,000

1,000

0 Double clear

Double green

Triple clear

Double lowE Triple super lowE Triple HM lowE

  Figure 73 Effect of the shading devices on the peak power demand of an air-conditioner for an old versus an R-2000 house model (Halifax, NS).

PAYBACK RETURN PERIODS The payback return period is defined as the number of years that would take to repay the original investment of a technology. The payback return period may be considered as one of the criteria to select an energy-efficient and cost-effective fenestration system. It is calculated as the ratio of the total cost of the fenestration system (including the capital, installation, operation and maintenance cost, etc.) to the cost-equivalent of its lifespan benefits (energy and non-energy). While the energy benefits of a fenestration system can easily be translated into cost, the non-energy benefits such as those related to the occupant comfort and the quality of the indoor environment cannot be meaningfully translated into dollars. The value of moisture control is also difficult to account for. Furthermore, the operation and maintenance costs are often not available a priori. Given these limitations, we defined the payback return period as the ratio of the capital cost of a shading device to the total annual energy cost. The following assumptions were used: • •

The effect of the shading devices on the size of the heating and cooling equipment was not accounted for. Shading devices installation costs were not accounted for. This may be particularly true for interior shading devices, which can easily be installed by homeowners. However, for exterior shading devices the installation cost may reach up to $100 per unit (Grieve, 2009).

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• •

The fuel costs (for house heating and cooling) were calculated based on published data for the year of 2008 without any future or time-of-use rate adjustments. This is a simple payback calculation, which does not account for future costs, interest rates, opportunity or promotional costs, etc.

Table 9 shows the total capital cost of the selected shading devices when used to fit the windows of the studied house, and the average cost per unit of window rough surface area (including the frame and glass sections). The house has a total window rough surface area of 30.3 m2. Table 10 summarizes the payback return periods of the studied shading devices. When compared with typical interior blinds, interior or between-pane reflective blinds do not seem to be cost-effective for any house type in any of the four selected Canadian cities. The cheapest brands of interior highly-reflective screens (with similar performance as the SilverScreen product) could be cost effective, particularly for old houses in cities where the fuel cost is high (such as Halifax). For old houses, the payback return period may range from 16 years for Halifax (highest fuel cost) to 32 years for Winnipeg (cheapest fuel cost). For R-2000 houses, the payback return period is longer, and may range from 39 years for Montreal to 57 years for Halifax. The payback return periods for the expensive exterior shading devices is even longer (more than 38 years), exceeding the life expectancy of the shading devices. Despite these long payback periods, one should consider other merits resulting from the use of such expensive shading devices (e.g., a reduced risk of moisture condensation on the interior surfaces of windows and a positive effect on the occupant’s thermal comfort).

Table 9 Cost of shading devices to fit the house windows. Type of shading

Interior

device Æ

aluminium blinds

Interior screens

exterior screens

exterior insulating rollshutters

(1” slats) Total cost ($)

1,061

2,182 to 8,545

11,393

15,332

Unit cost ($/m2)

35(1)

72(1) to 282(3)

376(2)

506(2)

(1)

Prices are for the cheapest brands, taken from www.blinds.ca (accessed in June 2009). Prices are for the Talius’s products (www.talius.com). (3) Prices are for the SilverScreen Lutron’s products (www.lutron.com). (2)

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Table 10

Simple payback return periods (in years) of the studied shading devices for old houses with double clear windows, and R-2000 houses with double clear low-e windows.

Shading Type

Ottawa, ON Old R-2000 houses houses

Montreal, QC

Winnipeg, MB

Halifax, NS

Old houses

Old houses

R-2000 houses

Old houses

R-2000 houses

R-2000 houses

Interior reflective blinds

NCE(1)

NCE

NCE

NCE

NCE

NCE

NCE

NCE

Interior reflective screens

22(2)

53

18

39

32

63

16

57

NCE

NCE

NCE

NCE

NCE

NCE

NCE

NCE

Exterior screens

72

103

65

98

92

136

38

83

Exterior rollshutters

74

115

69

97

94

145

40

78

Betweenpane reflective blinds (3)

(1)

NCE means the shading device is not cost-effective (negative payback period). Payback period is for the cheapest product (see Table 9). (3) Note: the cost of between-pane blinds is assumed to be equal to that of interior blinds. (2)

CONCLUSIONS This study presented guidelines for the effective use of solar shading devices for residential windows installed in old (year 1980), current and future (low-energy or net-zero energy) houses under typical Canadian cold climates. The R-2000 construction standard was used for the current and future house constructions. Various combinations of window and shading device types were considered. Window types included conventional windows for the old type of houses, and high performance windows for the current and future type of houses. Shading device included: typical interior blinds (commonly used by homeowners), interior highly reflective metallic blinds, interior close-weave screens, between-pane highly reflective metallic blinds, exterior insulating rollshutters, and exterior close-weave black screens. Four Canadian cities were selected to study the energy performance of the various window and shading device combinations: Ottawa (Ontario), Montreal (Quebec), Winnipeg (Manitoba), and Halifax (Nova Scotia). The guidelines were developed using whole-building computer simulations with inputs from a survey on households’ usage and control of shading devices, and field measured energy performance data collected for selected shading devices. To assist homeowners and building developers in selecting energy-efficient and cost-effective shading and window systems, several performance metrics were developed, encompassing the performance of the system before and after its installation in houses. The

94

payback return periods were also estimated. Due to the various metrics, a proper selection of a shading and window system often requires a trade-off among the system energy performance, the cost of the shading device, the visual and thermal comfort of the household occupants and the aesthetic considerations. Tables 11 to 14 summarize the cost-effectiveness of the studied shading devices. The following findings are highlighted: As traditionally proclaimed, windows with high solar heat gains and low U-factors are the best candidates for all construction types of houses in cold climates. In both old and current houses double green windows (glazing SHGC = 0.48; glazing U-Factor = 2.79 W/m2K) do not perform as well in terms of annual energy savings despite their significant potential to reduce the summer cooling energy (by 22% to 33%), and summer peak cooling power demand (by more than 11%) compared with double clear windows. Double clear windows with low-e coating and argon gas (SHGC = 0.65; U-Factor = 1.67 W/m2K) seem to be a cost-effective option for both renovation of old houses or building of new houses when compared, for example, with triple clear super low-e windows (SHGC = 0.36; U-Factor = 0.94 W/m2K). Triple clear reflective (with a sandwiched heat mirror polyester film HM88) low-e windows (SHGC = 0.47; U-Factor = 0.66 W/m2K) are another better, but expensive renovation option. Note that windows with typical interior blinds (the most widely used shading devices in Canada) are not energy-efficient nor cost-effective in terms of annual energy savings compared to un-shaded windows, but they may reduce the cooling energy use and cost (by up to 12%), and the on-peak cooling power demand (by up to 12%). Of course, they are used for many other reasons, primarily for visual privacy, and glare and solar heat control. Exterior insulating rollshutters and close-weave screens are the most effective shading devices to reduce the house heating and cooling energy use, the on-peak cooling power demand, and the risk of moisture condensation on the interior surfaces of windows. They were also shown to improve the thermal comfort conditions near windows (e.g., window interior surface temperatures are several degrees higher with rollshutters than with typical interior blinds). Rollshutters and screens are more effective when used with conventional windows (such as double clear windows) than when used with high performance windows. Their effect on the house total energy use is, however, not significant when they are used with super high performance windows (with U-factors < 1 W/m2K). They are, therefore, worthwhile to consider in renovating the vertical windows of old houses, particularly in regions where the risk of ice build-up on their surfaces is minimum and does not hinder their operation (rollshutters are not recommended for installation on roof windows). When compared with typical interior blinds of old houses with conventional double clear windows, rollshutters may reduce the annual heating energy use by 7%, the cooling energy use by more than 40%, and the on-peak cooling power demand by 18% to 42% (30% on average). When used in R-2000 houses with double clear low-e windows, rollshutters may reduce the annual heating energy use by 6%, the cooling energy use by more than 53%, and the on-peak cooling power demand by 29% to 48% (39% on average). The total annual energy cost savings depend on the house construction and the prevailing regional fuel cost, and may vary from $163 (Winnipeg, MB) to $385 (Halifax, NS) for old houses when compared with typical interior blinds. The cost savings for R-2000 houses are lower than those for old houses. Indoor relative humidity may be raised up to 40% during cold winter days (compared to 30% for un-shaded windows) without causing any significant moisture condensation on the interior window glass surfaces. Exterior rollshutters and screens are, however, expensive devices and their payback return periods are long (more than 38 years), most often exceeding their lifespan periods. When compared with typical interior blinds, between-pane reflective metallic blinds are not energy efficient nor cost-effective devices as they increase the annual heating energy use and cost (by up to 16%), particularly when integrated in high performance windows, despite their significant potential to 95

reduce the house annual cooling energy use (by more than 40%), and the on-peak cooling power demand (by 30% to 40%; 35% on average). They are, therefore, not recommended for use in Canadian residences for the purposes of annual energy saving, although they may have other benefits. If such metallic blinds have to be integrated in windows for one reason or another, they should be integrated in triple pane windows, and drawn up when open (instead of drawn down with slats horizontal) to reduce the effect of thermal bridges and increase the admission of solar heat gains indoors in the winter. Furthermore, to improve their energy performance, the use of alternative blind slat materials with low thermal conductivity materials is recommended (such as fibreglass, wooden or plastic). When compared with typical interior blinds, interior reflective close-weave screens (with low emissivity coating on the reflective surface) are effective shading devices, particularly to reduce the house annual cooling energy use and cost (by up to 25%) and the on-peak cooling power demand (by 13% on average), without a negative effect on the heating energy use. The total annual energy cost savings may vary from $68 (Winnipeg, MB) to $132 (Halifax, NS) for old houses. The cost savings for R-2000 houses are lower than those for old houses. Furthermore, reflective screens would not result in excessive risk of high glass temperatures and breakage if the air space between the shading device and the window is well naturally or mechanically ventilated. However, such screens may exacerbate the risk of moisture condensation on the interior surfaces of windows (indoor relative humidity should be lower than 15% to avoid moisture condensation during winter). The cheapest brands of such screens could be costeffective, particularly if they are installed in old houses in cities with high fuel costs such as Halifax. The payback return period for old houses may range from 16 years for Halifax (highest fuel cost) to 32 years for Winnipeg (cheapest fuel cost). Interior reflective blinds are also quite effective shading devices, particularly to reduce the house cooling energy use and cost (by up to 15%), and the on-peak cooling power demand (7% on average) when compared with interior typical blinds. However, they are not cost-effective when compared with typical interior blinds. Metallic reflective blinds would not significantly increase the risk of moisture condensation on the interior window surface, and would not result in excessive risk of high glass temperatures and breakage if the air space between the blinds and window is well ventilated (as is the case when the blinds are mounted on the window frames, not inside the frames). To reduce their effect on the heating energy use, the blinds should be operated in such a manner as to increase the admission of solar heat gains indoors (drawn up when open in winter instead of drawn down with slats horizontal).

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Table 11 Annual total energy cost savings of shading devices for old houses with conventional double clear windows and R-2000 houses with double clear low-e windows in Ottawa, Ontario. Shading Type ↓ Compared with Æ Exterior rollshutters

R-2000 houses

no shades

Old houses

typical interior blinds

no shades

typical interior blinds

$149

$133

$259

$208

$126

$110

$210

$158

Between-pane blinds

-$41

-$57

$44

-$8

Interior reflective screens

$57

$41

$152

$100

$4

-$12

$43

-$9

Exterior screens

Interior reflective blinds

Table 12 Annual total energy cost savings of shading devices for old houses with conventional double clear windows and R-2000 houses with double clear low-e windows in Montreal, Quebec. Shading Type ↓ Compared with Æ Exterior rollshutters

R-2000 houses

no shades

Old houses

typical interior blinds

no shades

typical interior blinds

$173

$158

$254

$222

$132

$116

$207

$175

-$143

-$158

-$13

-$44

Interior reflective screens

$71

$56

$151

$119

Interior reflective blinds

-$16

-$31

$4

-$28

Exterior screens Between-pane blinds

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Table 13

Annual total energy cost savings of shading devices for old houses with conventional double clear windows and R-2000 houses with double clear low-e windows in Winnipeg, Manitoba.

Shading Type ↓ Compared with Æ Exterior rollshutters

R-2000 houses

no shades

Old houses

typical interior blinds

no shades

typical interior blinds

$113

$106

$209

$163

$91

$84

$170

$124

Between-pane blinds

-$59

-$65

$25

-$21

Interior reflective screens

$41

$35

$114

$68

Interior reflective blinds

-$7

-$14

$24

-$23

Exterior screens

Table 14

Annual total energy cost savings of shading devices for old houses with conventional double clear windows and R-2000 houses with double clear low-e windows in Halifax, Nova Scotia.

Shading Type ↓ Compared with Æ Exterior rollshutters

R-2000 houses

no shades

Old houses

typical interior blinds

no shades

typical interior blinds

$200

$197

$453

$385

$140

$138

$366

$299

-$258

-$260

-$28

-$95

Interior reflective screens

$41

$38

$199

$132

Interior reflective blinds

-$72

-$75

$16

-$51

Exterior screens Between-pane blinds

98

REFERENCES Arasteh D., Goudey H., Huang J., Kohler C., Mitchell R. 2008. Performance Criteria for Residential Zero Energy Windows. Lawrence Berkeley National Laboratory, Report #: LBNL-59190. Accessed in June 2008. URL: http://gaia.lbl.gov/btech/papers/59190.pdf ASHRAE. 2005. Handbook of fundamentals. American Society of Heating, Refrigerating, and Air-conditioning Engineers. Atlanta. Clear R.D., Inkarojrit V., Lee E.S. 2006. Subject responses to electrochromic windows. Lawrence Berkeley National Laboratory. Report # LBNL-57125. URL: http://repositories.cdlib.org/lbnl/LBNL-57125. Accessed in December 2007. CMHC. 2008. Moisture and air. Householder’s Guide - problems and remedies. Canada Mortgage and Housing Corporation. pp. 1-28. ESRU. 2008. ESP-r version 11.3 Energy Systems Research Unit. University of Strathclyde. Glasgow. URL: http://www.esru.strath.ac.uk/ Fauteux A. et De Palma F. 2008. Le chauffe-eau instantané : de la pub à la réalité. La maison du 21e siècle, 15 (1), pp. 16-19. Fisekis K., Davies M., Kolokotroni M. Langford P. 2003. Prediction of discomfort glare from windows. Lighting Research & Technology, 35(4), pp. 360-371. Galasiu A.D., Laouadi A., Armstrong M., Swinton M.C., Szadkowski F. 2009. Field summer performance of interior reflective screens for residential windows. 11th IBPSA’s Building Simulation Conference; Glasgow, Scotland; July 27-30, 2009, pp. 1-8. Grieve J. (Business Development Manager, Talius Ltd.) July 2009. Personal communication. Hydro Quebec. 2008. Comparison of Electricity Prices in Major North American Cities. HydroQuébec, Montreal, Quebec. IEA. 2007. Annex 50. Prefabricated Systems for Low Energy Renovation of Residential Buildings. International Energy Agency. URL: http://www.ecbcs.org/annexes/annex50.htm; Accessed December 2007. IESO. 2009. Electricity pricing for residential consumers. Independent Electricity System Operator. URL: www.ieso.ca/imoweb/siteShared/smart_meters.asp?sid=ic. Accessed in February 2009. ISO. 2003a. Standard 15099: Thermal performance of windows, doors and shading devices detailed calculations. International Standard Organisation, Geneva, Switzerland. ISO. 2003b. Standard 9050: Glass in building-determination of light transmittance, solar direct transmittance, total solar energy transmittance, ultraviolet transmittance and related glazing factors. International Standard Organization. Geneva, Switzerland. Laouadi A. 2009a. Thermal performance modeling of complex fenestration systems. Journal of Building Performance Simulation, 2(3), pp. 189 — 207. Laouadi, A. 2009b. Thermal modeling of shading devices of windows. ASHRAE Transactions, 115(2), pp. 1-20.

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Laouadi A., Galasiu A.D., Swinton M.C., Armstrong M., Szadkowski F. 2009. Field performance of exterior solar shadings for residential windows: Summer results. 12th Canadian Conference on Building Science and Technology, Montréal, Quebec, May 2009, pp. 197-210. Laouadi A., Galasiu A.D., Swinton M.C., Manning M.M., Marchand R.G., Arsenault C.D., Szadkowski F. May 2008. Field performance of exterior solar shadings for residential windows: Winter results. IBPSA-Canada eSim Conference, Quebec City. pp. 1-8. URL: http://irc.nrccnrc.gc.ca/pubs/fulltext/nrcc50467/ Laouadi A., Parekh A. 2007. Complex fenestration systems: towards product ratings for indoor environment quality. Lighting Research and Technology, 39(2), pp. 109-122. URL: http://irc.nrccnrc.gc.ca/pubs/fulltext/nrcc45654/ Laouadi A., Arsenault A.C. 2006. Validation of skylight performance assessment software. ASHRAE Transactions, 112(2), pp. 1-13. Manning M.M., Swinton M.C., Ruest K. 2006. Assessment of reflective interior shades at the Canadian centre for housing technology. CCHT Report B-6020. National Research Council Canada, Ottawa. Manning M.; Swinton, M.C.; Szadkowski, F.; Gusdorf J.; Ruest K. 2005. The Effects of Thermostat Setting on Seasonal Energy Consumption at the CCHT Research Facility. CCHT Report. MINEFI. 2005. Document pour remplir la déclaration des revenus de 2005, Ministère de l’économie des Finances et de l’emploi, France. URL: http://www2.finances.gouv.fr/calcul_impot/2006/pdf/form-2041-GR.pdf NFRC. 2004a. NFRC-100: Procedure for determining fenestration product U-factors. National Fenestration Rating Council, Silver Spring, MD. NFRC. 2004b. NFRC- 200: Procedure for determining fenestration product solar heat gain coefficient and visible transmittance at normal incidence. National Fenestration Rating Council, Silver Spring, MD. NRC. 2006. SkyVision version 1.2: National Research Council of Canada. URL: http://irc.nrccnrc.gc.ca/ie/lighting/daylight/skyvision_e.html. Accessed in August 2008. NRCan. August 2006. Energy Use Data Handbook, 1990 and 1998 to 2004. Natural Resources Canada URL: http://www.oee.nrcan.gc.ca/Publications/statistics/handbook06/pdf/handbook06.pdf; Accessed in December 2007. NRCan, April 2005. R-2000 Standard. Natural Resources Canada. Ottawa. NRCan. December 2003. Survey of household energy use. Summary report. Natural Resources Canada. Ottawa. StatsCan. September 2008. Energy Statistics Handbook, Catalogue No. 57-601-X. Statistics Canada. Ottawa. Strachan P.A., Kokogiannakisa A. G., Macdonalda I.A. 2008. History and development of validation with the ESP-r simulation program. Building and Environment 43. pp. 601–609. Tariku, F.; Kumaran, M.K.; Fazio, P. 2008. Thermostat setback effect in whole building performance. Proceedings of Building Physics Symposium, Leuven, Belgium. pp. 1-5.

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Veitch J.A., Mancini S., Galasiu A.D., Laouadi A. 2009. Survey on Canadian Households' Control of Interior Climate. Report B-3243.2. NRC Institute for Research in Construction, pp. 1-85.

ACKNOWLEDGMENT This work was supported by the Institute for Research in Construction of the National Research Council Canada (NRC-IRC), CETC Buildings Group of Natural Resources Canada (NRCan), Canada Mortgage and Housing Corporation (CMHC), Ontario Power Authority, Hydro Québec, Gas Métro, Pilkington North America Inc., Prelco-Thermalite Inc., Talius Limited, and Lutron Electronics Co. Inc. The author is very grateful for all these contributions and support. The author would also like to acknowledge the contribution of his NRC-IRC colleagues Anca Galasiu, Jennifer Veitch, Sandra Mancini, Marianne Armstrong, Chantal Arsenault, Roger Marchand, Mike Swinton, Frank Szadkowski, as well as that of visiting students Dominic Robillard, and Emilie Thibault, for their valuable assistance in this work.

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APPENDIX A: METHODOLOGY FOR BUILDING-ENERGY COMPUTER SIMULATION The simulation methodology used two advanced computer simulation programs, ESP-r (ESRU, 2008) and a new in-house version of SkyVision (NRC, 2006), to compute the annual energy and hourly peak demands for heating and cooling of Canadian residences. The geometry of a full-size existing single detached house was used to model and perform the computer simulations. The main variables of the simulation study focused primarily on the combination of several types of windows and shading devices, construction materials for the current and old house construction technologies, and regional weather data. Other house inputs, which do not relate directly to the simulation variables studied, were kept constant. Details of the simulation methodology follow.

ESP-R COMPUTER PROGRAM ESP-r is an integrated modeling tool used to simulate the thermal, visual and acoustic performance of buildings and to assess the energy use and gaseous emissions associated with the environmental control systems and construction materials. ESP-r has gone through intensive validation studies for several years through projects of the International Energy Agency and CEN standards, and through various large-scale international projects. More details on these validation studies may be found in Strachan et al. (2006) and on the ESRU web site (www.esru.strath.ac.uk). ESP-r uses detailed inputs for the house geometry and envelope construction materials, and local hourly weather data. ESP-r performs calculations on a time step base, which is selected by the user. This simulation study used a 15-minute time step.

SKYVISION COMPUTER PROGRAM SkyVision is a computer tool used to calculate the thermal, optical and daylighting performance of skylights, windows, and shading devices. The new in-house version of SkyVision features advanced thermal models of various types of shading devices such as slat-type blinds, drapes, and screens. Past and new versions of SkyVision have been validated using data from field measurements conducted at NRC, as well as data from other published sources (Laouadi and Arsenault, 2006; Laouadi, 2009a,b). In this simulation study, SkyVision was used to compute the ESP-r inputs for the optical and thermal performance of windows and shading devices. A performance database of window and shading device combinations was generated and subsequently linked to the ESP-r database manager to perform the thermal simulations. The performance data include angular profiles of the solar transmittance, SHGC and solar absorptance at each layer of the window and shading system, U-factor of the window-shading system, and thermal resistance of the air gaps between the window system layers.

HOUSE GEOMETRY MODEL The simulation model house used the geometry of the Reference House of the Canadian Centre for Housing Technology (CCHT; http://www.ccht-cctr.gc.ca/). The CCHT house is a single detached, two storey house. According to a 2003 Canadian household survey, single detached houses made up about 65% of all dwelling types in Canada (NRCan, 2003). The CCHT house is a replicate of a popular house model on the local residential market in Ottawa, Ontario. The house includes an unoccupied basement space, two occupied ground and second floors, and an attached garage space. The total livable (heated) surface area of the house is 254 m2 (2734 ft2). The CCHT house model is designed to take advantage of passive solar heating by using extensive windows on the south and north walls. There are 14 windows with a total glass surface area of 24.22 m2 (9.5 % of the livable surface area), distributed as follows: four

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south-facing windows (glass surface area 10.46 m2); seven north-facing windows (10.9 m2); one westfacing window (1.29 m2) and two east-facing windows (1.67 m2). The window frames, which represent about 25% of the window rough opening surface area, were simulated as independent surfaces attached to the window walls. Figure 74 shows the CCHT house model as simulated (note that some windows belonging to the same wall were grouped together). It should be noted that the size (in terms of the heated surface area) of the CCHT house model is above the surface area of the average Canadian house (with a heated surface area of 147.5 m2, NRCan, 2003). Although the heated house area is directly linked to the house energy use, it is expected that the house size would not have any effect when comparing the relative house performance due to given changes in the design variables with another reference house with similar form and size.

West facade

South facade

  Figure 74 The CCHT house geometry model as simulated. Note that the window frames were treated as separate surfaces. The house is oriented north-south.

HOUSE CONSTRUCTION House construction materials vary over time and have considerable effect on the energy use of a house. A 2003 household survey (NRCan, 2003) found that almost 60% of Canadian dwellings were constructed after 1969. In this study, two construction types were considered to reflect the current and old construction trends. The current construction trend across Canada uses the R-2000 standard (NRCan, 2005), which improves the energy-efficiency of new houses. Table 15 summarizes the technical requirements of the R-2000 standard. Houses built according to this standard are tight and reduce air infiltration energy losses. The air leakage in terms of the air changes per hour at a pressure differential of 50 Pascal, and the effective leakage area at a pressure differential of 10 Pascal of an R-2000 house are set to 1.64 ACH and 479 cm2, respectively, as measured at the CCHT house. The old construction materials vary from year to year and from region to region. Old houses are usually much leakier than current houses. This study used typical construction technologies for the year of 1980 for a given region. According to the 2003 Canadian household survey, houses built between 1970 and 1989 represent 39% of the total house stock. The technical data of the 1980 construction and the air leakage characteristics

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were drawn from the construction database compiled by the NRCan’s Office of Energy Efficiency in 2006. Table 16 summarizes the construction details of an old house built in 1980 in Ottawa, Ontario. For other Canadian cities, Table 16 can still be used, but with proper regional insulation values for the house envelopes. Table 17 lists the insulation values and air leakage characteristics for the three Canadian cities used in this study. Table 15 Construction material details of current houses built according to the R-2000 standard.

Envelope Assembly 2

foundation floor (U = 1.275 W/m K) foundation wall (U =0.231 W/m2K)

Layer Descriptions 75 mm light mix concrete 150 mm gravel bed (exterior) 13 mm gypsum board (interior) 136 mm batt insulation (RSI 3.4) 19 mm air space 200 mm light mix concrete (exterior)

Exterior walls (U = 0.225 W/m2K)

13 mm gypsum board (interior) 154 mm batt insulation (RSI 3.85) 13 mm chipboard 25 mm air space 90 mm brick veneer (exterior)

Garage interior wall (U = 0.24 W/m2K)

13 mm gypsum board (interior) 154 mm batt insulation (RSI 3.85) 13 mm chipboard (garage side)

Ceiling (U = 0.11 W/m2K)

13 mm gypsum board (interior) 352 mm batt insulation (RSI 8.8)

Floor between storeys (U = 0.94)

25 mm carpet (interior) 15 mm rubber underlayment 13 mm plywood 89 mm air space 13 mm gypsum board

Floor above basement (U = 1.261 W/m2K)

25 mm carpet (interior) 15 mm rubber underlayment 13 mm plywood

Floor above garage (U = 0.124 W/m2K)

Attic roof (U = 3.84 W/m2K)

25 mm carpet (interior) 15 mm rubber underlayment 13 mm plywood 89 mm air space 280 mm batt insulation (RSI 7.0) 13 mm chipboard 13 mm chipboard (interior) 5 mm asphalt shingle

Exterior door (U = 3.316 W/m2K) 2

Garage door (U = 5.88 W/m K)

25 mm oak 0.5 mm steel

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Table 16 Construction material details for old houses built in 1980 in Ottawa, Ontario.

Envelope Assembly 2

Foundation floor (U = 1.275 W/m K)

Foundation wall (U = 0.435 W/m2K)

Layer Descriptions 75 mm light mix concrete 150 mm gravel bed (exterior) 64* mm batt insulation (RSI 1.6) 200 mm light mix concrete (exterior)

Exterior walls (U = 0.354 W/m2K)

13 mm gypsum board (interior) 93.2* mm batt insulation (RSI 2.33) 13 mm chipboard 25 mm air space 0.5 mm Aluminium siding (exterior)

Garage interior walls (U = 0.377 W/m2K)

13 mm gypsum board (interior) 93.2* mm batt insulation (RSI 2.33) 13 mm chipboard

Ceiling (U = 0.195 W/m2K)

13 mm gypsum board (interior) 196* mm batt insulation (RSI 4.9)

Floor between storeys (U = 0.94 W/m2K)

25 mm carpet (interior) 15 mm rubber underlayment 13 mm plywood 89 mm air space 13 mm gypsum board

Floor above basement (U = 1.261 W/m2K)

25 mm carpet (interior) 15 mm rubber underlayment 13 mm plywood

Floor above garage (U = 0.309 W/m2K)

25 mm carpet (interior) 15 mm rubber underlayment 13 mm plywood 93.2* mm batt insulation (RSI 2.33) 13 mm chipboard

Attic roof (U = 3.84 W/m2K)

13 mm chipboard (interior) 5 mm asphalt shingle

Exterior doors (U = 3.316 W/m2K) 2

Garage door (U = 5.88 W/m K)

25 oak 0.5 mm steel

*

Insulation values vary with cities. For other Canadian cities, substitute the insulation values in Table 16 with the ones listed in Table 17 below.

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Table 17

Regional insulation R-values and air leakage characteristics of old house constructions built in 1980 (data taken from the 2006 database of NRCan’s Office of Energy Efficiency).

City

Leakage (ACH)

Leakage Area (cm2)

Attic insulation (RSI)

Exterior wall insulation (RSI)

Foundation wall insulation (RSI)

Ottawa, ON

4.7

1131

4.9

2.33

1.6

Winnipeg, MB

2.38

486

6.2

2.22

1.94

Montreal, QC

6.62

1114

3.6

1.53

1.21

Halifax, NS

4.92

1224

4.89

2.62

1.74

WINDOW TYPES The NRC household survey (Veitch et al., 2009) found that the most common window types used in single detached houses were double glazed windows (44%), followed by a substantial number of high performance windows (22%). High performance windows have become standard practice in current houses. In this study, several types of conventional and high performance windows were used to simulate houses with both old and current construction technologies. Super high performance windows were also used to generate information on low-energy or net zero energy houses across Canada. Conventional window types included: double and triple clear glass windows to maximize daylight and solar heat gains, and double green glass windows to control solar heat gains in summer while providing adequate daylight in winter and summer. High performance windows included double clear glass with low-e coating (on surface # 3) and 95% of argon gas fill. Super high performance windows included triple clear glass windows with two low-e coatings (on surfaces #3 and #5) and 95% krypton gas fill, and triple clear glass windows with a between-pane solar reflective polyester heat mirror (HM88). Three low-e coatings were used on surfaces #2, #3, and #5. Metallic and insulating spacers were used with the conventional and high performance windows, respectively. A standard wood frame was used with all window types with a U-factor of 2.78 W/m2K (ASHRAE, 2005). The frame surface area represents about 25% of the window rough opening area. Table 18 lists the details of the window types with their performance metrics.

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Table 18

Details of the simulated window types. Note that the performance metrics are calculated for a standard size window (0.6 m wide x 1.5 m tall).

Window Type

Double Clear (With metallic spacer)

Double Green (With metallic spacer) Triple Clear (With metallic spacer)

Double Clear Low-e (ε3 = 0.157) (With insulating spacer) Triple Clear Super Low-e (ε2 = 0.042, ε5 = 0.157) (With insulating spacer)

Triple Clear Reflective Low-e (ε2 = ε5 = 0.05; ε3 = 0.122) (With insulating spacer)

Description

Performance Indices (centre of glass section)

VT (%)

SHGC (%)

U-Factor (W/m2K)

6 mm Pilkington Optifloat clear 13 mm air(1) 6 mm Pilkington Optifloat clear

78

70

2.61

6 mm Pilkington Optifloat green 13 mm air(1) 6 mm Pilkington Optifloat clear

67

48

2.61

70

61

1.71

6 mm Pilkington Optifloat clear 13 mm 5% air & 95% argon(1) 6 mm Pilkington Energy Advantage Low-e

73

65

1.6

6 mm Cardinal Low-e-272 clear 13 mm 5% air & 95% argon 6 mm Pilkington Optifloat clear 13 mm 5% air & 95% argon(1) 6 mm Pilkington Energy Advantage Low-e

57

36

0.82

68

47

0.52

6 mm Pilkington Optifloat clear 13 mm air 6 mm Pilkington Optifloat clear 13 mm air(1) 6 mm Pilkington Optifloat clear

3.85 mm clear Glaverbel Planibel Top Low-e 13 mm 5% air & 95% krypton 0.076 mm Southwall Heat Mirror HM88 13 mm 5% air & 95% krypton(1;2) 3.85 mm clear Glaverbel Planibel Top Low-e

1)

If the window employs between-pane blinds, the thickness of the gas space is set to 20 mm and the gas mixture is replaced by air. (2)

Although such window with between-pane blinds might not be commercially available, it was used in this report for consistency purposes with other shading devices.

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SHADING DEVICE TYPES According to the NRC household survey (Veitch et al., 2009), interior shading devices are ubiquitous (with 96% of usage) in detached houses across Canada. The survey found very little usage of exterior or between-pane shading devices. Interior curtains or drapes, and blinds are equally used in detached houses (30% of usage each). Roller screens scored about 20%. Three types of shading devices with potential energy savings were considered in this study. The selected shading devices may be placed outside or inside the windows, or between the window glass panes. The exterior shading devices included insulating rollshutters and close-weave black roller screens. The interior shading devices included reflective close-weave roller white screens (reflective surface faces window), and reflective (white) and typical (light grey) horizontal blinds. The between-pane shading devices included reflective (white) horizontal blinds. All these shading products are commercially available. Table 19 lists the details of each shading device.

OPERATIONAL SCHEDULE OF SHADING DEVICES The operation schedule of shading devices varies with the time of day and season. The NRC household survey (Veitch et al., 2009) found that more than 76% of households opened their shading devices during daytime in winter for view out and daylight admission, and closed them at night for privacy and darkness. In summer, however, about 50% of households opened or closed their shading devices during daytime. Based on this information, the shading devices in this simulation study were assumed open from 8:00 AM to 6:00 PM, and closed during the remaining hours of winter days. During summer days, shadings on the south, east and west–facing windows were assumed to be closed day and night, and shadings on the north-facing windows were assumed to be open during daytime from 7:00 AM to 9:00 PM, and closed during the remaining hours.

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Table 19 Detailed descriptions of the simulated shading devices. Shading Device Type

Description •

Exterior insulating rollshutters

Exterior screen shades

• • • • • • • • • • • •

Between-pane reflective Venetian blinds

• • • • • •

Interior reflective roller screens

• • • • • • •

Interior reflective Venetian Blinds

• • • • • • •

Typical interior Venetian Blinds

• • •

Comments

6 mm insulated aluminium (1 mm Aluminium alloy + 5 mm polyurethane insulation). Thermal average conductivity = 0.18 W/mK Density = 14061 kg/m3 Specific heat = 68 J/kgK Emissivity = 0.8 Colour: beige (solar reflectance = 0.66)

• • •

• 0.53 mm PVC coated Fibreglass yarns Thermal conductivity = 0.15 W/mK Density = 1380 kg/m3 Specific heat = 1000 J/kgK Emissivity = 0.8 Colour: charcoal (opaque material with solar reflectance = 5%) Openness factor = 5 %

• •

• Slat width = 12.7 mm Slat spacing = 12.7 mm Slat thickness = 0.2 mm Slat emissivity = 0.8 Slat colour = white (solar reflectance = 70%). Slat angle = (0o-open; 89o closed)

• •

• 0.5 mm PVC coated fibreglass yarns Thermal conductivity = 0.15 W/mK Density = 1380 kg/m Specific heat = 1000 J/kgK Front & back emissivity = 0.16 & 0.83 Colour: white with aluminium coating on the front surface (material front/back solar reflectance = 77% & 71%). Openness factor = 4 %

• • • •

Slat width = 25.4 mm Slat spacing = 20 mm Slat thickness = 0.2 mm Slat height = 2 mm Slat emissivity = 0.8 Slat colour = white (solar reflectance = 70%) Slat angle = (0o-open; 75o closed) Same slat dimensions as above Slat emissivity = 0.82 Slat colour = grey (solar reflectance = 42%)

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• • • • •

Employed with side rails and rubber gaskets. Enclosed air space between shutter and window is assumed sealed. Shutter distance to window = 180 mm

Employed with side rails and rubber gaskets. Enclosed air space is assumed not sealed due to perforation. Screen distance to window = 180 mm.

Blinds placed in the middle of a 20 mm air space. Spectral data taken from the WIS program database v3.0 (WinDatDEF#01) Slat surfaces are assumed diffuse

Enclosed air space between screen and window is assumed open at the top, bottom and side sections (with an opening ratio = 15%). Screen distance to window = 160 mm. Spectral data taken from the WIS program database v3.0 (SilverScreenWhite ED01). Screen opaque surface is assumed diffuse Enclosed air space between blinds and window is assumed open at the top, bottom and side sections (opening ratio = 15%). Blind distance to window = 160 mm. Spectral data taken from the WIS program database v3.0 (WinDatDEF#01) Slat surfaces are assumed diffuse Same as above Spectral data taken from the WIS program database v3.0 (Luxaflex6004)

HOUSE INTERIOR HEAT GAINS Interior heat gains from occupants, lights, receptacles, appliances and other equipment greatly influence the energy use of houses. In this study, the model house was assumed to be equipped with a standard set of major appliances typically found in North American homes. The appliances and equipment that released heat to the indoor air included a stove, dishwasher, and a fridge located on the ground floor; and a dryer, washer, and hot water tank located in the basement. The lighting fixtures and receptacles were distributed equally on the ground and second floors. Interior heat gains are a function of the occupancy density and schedule. According to the NRC household survey (Veitch et al., 2009), the average house occupancy included three people. This occupancy is close to the average occupancy in Canadian residences (2.4 people) (NRCan, 2003). The NRC survey also found that the houses are partially occupied (42%) during daytime hours (9:00 AM to 6:00 PM). The typical heat release from an adult person performing a normal household activity is estimated at 63 W of sensible heat and 54 W of latent heat (from moisture). The heat release from lights, receptacles, appliances and equipment, the electrical data and operation schedule of the CCHT house were used with the following assumptions: • • • •

Half of the electrical power use of the dishwasher goes to the air space; All of the electrical power use of the fridge and stove go to the air space; No heat release from washer, but 15% of the power use of the dyer goes to the air space; Heat gain from the water heater is constant and equal to 89 W (Fauteux and De Palma, 2008). Table 20 summarizes the hourly interior heat gains per thermal zone of the model house. The total daily interior heat gains of the model house are 14.417 kWh.

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Table 20 Hourly interior heat gains of the simulated model house. Thermal Zone Time (hr.) 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Ground & second floors People (fraction) 1 1 1 1 1 1 1 1 0.42 0.42 0.42 0.42 0.42 0.42 0.42 0.42 0.42 1 1 1 1 1 1 1

Ground floor

Ground & second floors

Basement

Appliances (W) 45 44 46 46 45 52 58 529 58 46 45 46 405 46 62 61 51 736 71 289 49 48 125 68

Lights & receptacles (W) 5 5 5 5 5 5 59 340 7 5 5 5 82 5 5 5 5 161 503 508 246 238 238 9

Appliances (W) 89 89 89 89 89 89 89 89 89 89 89 89 89 89 89 89 89 89 89 249 89 89 89 89

HEATING AND COOLING EQUIPMENT Heating and cooling equipment and fuel types vary from region to region. According to the 2003 NRCan household survey (NRCan, 2003), 63% of Canadian households used a furnace as their main heating system. Over 80% were hot-air systems. Among other types of heating systems, electric baseboards were the most popular. Almost 45% of Canadian households used central or window air-conditioning systems, or heat pumps. Within Canada, there were significant regional differences in the market penetration rates of air-conditioning systems. The market penetration rate is the highest in Ontario (74%), followed by Quebec and the Prairies (32%), and British Columbia (18%). In this study, a hot air furnace was used with a fuel type dependent on the region. For a gas furnace, the efficiency was set equal to a medium efficiency of 78% for old house constructions, and 94% for current house constructions. For an oil furnace, the efficiency was set equal to a medium efficiency of 78% for old house constructions, and 85% for current house constructions. Electrical furnaces have an efficiency of 100%. The nominal power of the furnace circulation fan was set to 745 W (1hp). A typical residential air conditioner was used with a nominal capacity of 2 tons (24 000 BTU/h, or 7 kW) and a SEER (seasonal energy efficiency ratio) = 13, or a COP (coefficient of performance) = 3.43. 111

The heating and cooling equipment were operated according to typical indoor temperature controls, which were derived from the NRC household survey (Veitch et al., 2009). According to this survey, for heating in occupied areas, 75% of households set the thermostat temperature at 21oC throughout daytime, with a night-time set back at 19oC from 10:00 PM to 6:00 AM. The heating temperature set point for the basement space was fixed at 1oC lower than the ground floor. For cooling, 75% of households set the thermostat temperature at 24oC throughout the day. The basement space is not occupied and, therefore, not cooled (free floating).

CLIMATES AND REGIONS Climate conditions have a great impact on the energy use of buildings. In Canada, the energy requirements for heating and cooling vary from province to province due to different prevailing climates. In this study, four representative cold and slightly warm climates were considered: Ottawa (Ontario). Ottawa is located at 45°19 north latitude and 75°40 west longitude, has a semicontinental climate, with a warm, humid summer and a very cold winter. The daily average outdoor temperature may vary from -15° in winter to 26°C in summer, and the daily average sunshine hours may vary from 2.6 hours in winter to 8.9 hours in summer. Heating is the major concern in this city. Natural gas is the common fuel for hot-air furnace heating. Montreal (Quebec). Montreal is located at 45°28’ north latitude and 73°45’ west longitude, has a semicontinental climate, with a warm, humid summer and a very cold winter. The daily average outdoor temperature may vary from -13° in winter to 26°C in summer, and the daily average sunshine hours may vary from 2.6 hours in winter to 8.8 hours in summer. Heating is the major concern in this city. Electricity is the common fuel for hot-air furnace heating. Winnipeg (Manitoba). Winnipeg is located at 49°54’ north latitude and 97°14’ west longitude, has a cold continental climate with a short, warm summer and a long, very cold winter. The daily average outdoor temperature may vary from -23° in winter to 26°C in summer, and the daily average sunshine hours may vary from 3.2 hours in winter to 10.2 hours in summer. Heating is the major concern in this city. Natural gas is the common fuel for hot-air furnace heating. Halifax (Nova Scotia). Halifax is located at 44°39’ north latitude and 63°34’ west longitude, has an eastern-maritime climate, with a cold winter, and a short, warm summer. The daily average outdoor temperature may vary from -9° in winter to 23°C in summer, and the daily average sunshine hours may vary from 2.1 hours in winter to 7.7 hours in summer. Heating is the major concern in this city. Oil is the common fuel for hot-air furnace heating.

EXPERIMENTAL VALIDATION OF THE SIMULATION MODEL The simulation model, which combines ESP-r and SkyVision programs, was validated using field measurements collected at the CCHT experimental facility, located in Ottawa, Ontario. The simulation predictions for the indoor temperature and heating energy demand of the CCHT Reference house were compared with measured data from two-weeks of winter measurements (February 1-14, 2008). More details about the measurement procedure can be found in Laouadi et al. (2008) and Galasiu et al. (2009). The CCHT Reference house was built according to the R-2000 standard and features high performance double-glass windows (with low-e coating on surface #3, insulated spacer, and 95% argon gas concentration). During the field measurements, the windows of the Reference House were fitted with a

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mix of common interior horizontal Venetian blinds (on most windows) and vertical blinds (on patio glass door, dining room window and stairwell window). The slats of the Venetian blinds were slightly curved and made of aluminium with the following characteristics: slat spacing = 0.02 m, slat width = 0.025 m, slat visible reflectance = 63%. The vertical blinds were made of fabric with the following characteristics: slat spacing = 0.075 m, slat width = 0.090 m, slat visible reflectance = 71%. All the interior blinds were mounted outside the window frames, leaving an open air space between the blinds and the wall incorporating the window frames. During the measurements, the interior blinds were open during daytime from 9:00 AM to 5:00 PM, and closed during the remaining period. The CCHT house was equipped with a high efficiency hot air condensing furnace with a nominal capacity of 50 000BTU/h (15,000 kW) and an efficiency of 94%. The nominal power of the furnace fan was 745 W (1 hp). The thermostat set point temperature was fixed at 21oC. Data was collected every 5- minute and averaged every hour. A simulation model of the CCHT Reference house was created in ESP-r. SkyVision was used to calculate the optical and thermal inputs for the window and blind systems, which were subsequently exported to ESP-r. The ESP-r blind control feature was used to mimic the actual blind opening and closing schedule. The ESP-r furnace model was invoked to compute the hourly heating energy demand of the house. Simulations were conducted on an hourly basis. Figure 75 compares the predicted versus the measured heating energy demand (furnace and circulation fan) of the CCHT house for the two-week measurement period. The predictions compared within a 10% error with the measurements. The two-week measured energy use was 1416 kWh, whereas the predicted energy use was 1540 kWh. On an hourly basis, the predicted energy use was both lower and higher than the measured one. This difference may be attributed to the time step used in the simulation (Note: shorter time steps resulted in similar, but asynchronous fluctuations of the measured values; these are not reported here). Figure 76 shows a comparison between the predicted and the measured temperatures on the ground floor during a sunny and cold winter day. The predictions are in good agreement with the measurements.

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9000

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February 1 to 14, 2008

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Figure 75 Hourly averaged measured and simulated heating energy demands of the CCHT house with interior blinds in an open position (slats horizontal day and night).

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February 14, 2008 (sunny)

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Figure 76 Hourly averaged measured and simulated ground floor temperatures of the CCHT house with interior blinds in an open position during a cold, sunny winter day.

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APPENDIX B: LIST OF SHADING MANUFACTURERS Table 21

North American shading manufacturers (dealers) serving the Canadian market (data were derived from the internet).

Manufacturers (Dealers)

Contact Information

Product Types

3530 Boulevard des Entreprises Terrebonne, Québec, Canada J6X 4J8 Altex

Variety of interior fabric screens and blinds

Fax: (450) 968-0884 Phone: (450) 968-0880 Toll free: 1-800-363-5930 http://www.altex.ca Head Office P.O. Box 3279, 5501 - 46th Avenue S.E.

Talius Limited

Rollshutters

Salmon Arm, BC, Canada V1E 4S1 Toll free: 800.665.5550

Habitat retractable screens

Tel: 250.832.7777 Fax: 250.832.8577 Email: [email protected] http://www.talius.com K&F ROLLSHUTTER

7911-25 street

Dealer of Alulux: http://www.alulux.com

Edmonton, Alberta, Canada T6P 1N4

Rollshutters

Phone: (780) 440 1934 Tax: (780) 440 6565 http://www.rollshutter.ca/

Rolco Rollshutters

139 Fisher Street P.O. Box 381 Okotoks, AB Canada,T1S 1A6

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Rollshutters

Toll free: 800-733-0440 Phone: (403) 938-0303 Email: [email protected] http://www.rolco.com RR 7 St. Main Mols Insutec

2499 Bathurst 2nd Concession

Dealer of Alulux products

Perth, ON, K7H 3C9 Phone: 1-613-326-0386

Rollshutters

Awnings

Fax: 1-613-326-0593 e-mail: [email protected] http://www.mechoshadesystems.com/ Customer Service 7200 Suter Road Coopersburg, PA, USA 18036 Phone: (610) 282-3800 Lutron Electronics Corporation, Inc.

Toll free: (888) 588-7661

Variety of manual and motorized interior roller fabric shades and screens

Fax: (610) 282-3090 E-Mail: [email protected] http://www.lutron.com Canadian distributor in Ontario: J.M. Audio Centre 1366 Clyde Avenue, Ottawa, on k2c 3z4 Tel: 613- 723-2923 205 Adesso Drive Concord, Ontario, L4K 3C4 SunProject Toro

Interior roller shades and blinds

Phone: 905-660-3117 Fax: 905-660-3365

Exterior shades and blinds

Toll free: 1-888-836-6980

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Toll Fax: 1-800-728-8636 http://www.sunproject.com #1, 115 28th St. SE Nysan Solar Control (a division of Hunter Douglas)

Interior shades and blinds

Calgary, Alberta T2A 5K4, Canada Phone: 403-204-8675

Sun louvers

Toll free: 800-727-8953 Fax: 403-204-8676

Exterior blinds and screens

www.nysan.com Light shelves Corporate office Glen Raven, Inc.

1831 North Park Avenue

(North America)

Glen Raven, NC 27217-1100

Residential and commercial awnings

Phone: 336.227.6211 Fax: 336.226.8133 Roller fabric shades www.glenraven.com Canadian distributor: Trican Corporation Mississauga, Ontario Toll free: 1-800-387-2851 Phone: 1-905-795-1525 Fax: 1-905-795-1526

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