PASSIVE ENVIRONMENTAL CONTROL ...

Conference Proceedings of the American Solar Energy Society (ASES), SOLAR 2007, 7-12 July, Cleaveland, Ohio.

PASSIVE ENVIRONMENTAL CONTROL STRATEGIES FOR A COLD CLIMATE The Eugene-H-Kruger Building at Laval University André Potvin, M.Arch. PhD Claude Demers, M.Arch. PhD GRAP (Groupe de recherche en ambiances physiques) École d'architecture, Université Laval, (Québec), Canada, G1K7P4 [email protected], [email protected] www.grap.arc.ulaval.ca

ABSTRACT The Eugene-H-Kruger Building inaugurated in September 2005 marks a new step in Laval University infrastructure development strategy. This new laboratory integrates design principles that aim to reduce operating costs, especially energy use over the building’s life cycle. The GRAP (Groupe de recherche en ambiances physiques) was appointed to support the professionals in an integrated energy design process. A set of passive environmental control strategies combined with centralized heat recovery led to an estimated 32% reduction in operating energy consumption when compared with a reference building as defined by the Canadian MNECB (Model National Energy Code for Buildings). The all wood construction also led to a 40% reduction in embodied energy compared to a conventional all steel construction system. This paper describes more thoroughly the passive heating and cooling strategies as well as daylighting design of a typical heavy workshop section of the building.

buildings consist of pavilionary siting (fig. 1), special attention was addressed to the design of the general building volumetry at the initial phase to optimize favorable exterior microclimates. Figure 2 shows the ground floor plan with the heavy laboratories (A), light laboratories (B) and teaching sector (C). The main entry is therefore directly exposed to the morning sun of the south-eastern sector and self-protected from the dominant south-westerly and northeasterly winds by the heavy laboratory sector and its immediate built context. The external extension of the cafeteria in the main court also benefits from such a microclimate.

Keywords : passive heating, daylighting, passive cooling, energy, integrated design process.

1. INTRODUCTION The Kruger Pavilion consists of an imposing extension of the existing Forestry Faculty on its south-western side into a research laboratory. This research facility on wood engineering technology demonstrates the potential of an all wood structure to provide for the large 7600 m2 building surface that most importantly becomes the University’s first building integrating the principles of sustainable development. The L –shape building extension enables the optimization of external microclimates, daylighting opportunities as well as passive cooling and passive solar heating strategies. Whereas most of existing campus

Fig. 1: Site plan showing the protecting L-shape volumetry of the Kruger Building


The principal bioclimatic strategies (fig. 3) implemented in the heavy laboratories sector of the building are: • use of collecting walls perforated "Solarwall" to preheat the fresh air supply of the heavy laboratories and to minimize the risks of overheating of the south-west wall; • exploitation, at the moment of the greatest demand for heating, of the direct solar gains by the generous glazing of the south-eastern façades and clerestories; • occultation of the glazing in summer using custom fixed exterior sun shading devices made of frosted glass also acting as visible light reflectors; • introduction of extensive skylights in the heavy laboratories, bringing solar gains in period of heating and generous zenithal daylight • choice of interior finished strategically positioned and highly reflective to optimize ambient daylighting; • introduction of a thermal mass shifting daytime internal gains during the night.

C

B

A A -Heavy laboratories B -Light laboratories C -Teaching sector

the maximum passive solar gains in the morning on the SE façade at the peak of the heating demand. A single loaded corridor at ground level therefore opens up on sun bathed public spaces whilst roof monitors of the heavy laboratories section act as efficient sun catchers. The very low internal gain profile of the heavy laboratories and important ACH were compensated by the architectural integration of three sections of solar pre-heating system (SolarWall) on the SW façade that provide a 6% reduction in heating demand. Numerical simulations were conducted to establish possible energy savings by these various bioclimatic strategies. Energy simulations were therefore initially carried out by the software Energy-10 version 1.5. Early simulations suggested that a good daylighting strategy could have a major impact on passive solar heating and artificial lighting loads (Tab.1). The study was limited to a typical heavy workshop where passive heating and cooling strategies were more easily applicable. Simulated parameters related to the improvement of the heat insulation of the envelope, improvement of the thermal performance of glass of the windows, modification of the openings to allow a better contribution of daylight, installation of sun shading devices. Equipment operation, schedules, mechanical and electric systems parameters were not studied specifically. These simulations were based on reasonable, but approximate values available at the moment. TABLE 1: ENERGY PERFORMANCE

Fig. 2: Ground floor plan showing the three main sectors of the building

ANDRE - ANNUAL ENERGY USE Reference

Modèle proposé

300 281.7

224.0

kWh / m²

200

156.4

125.4

100 79.3

Fig. 3: Integrated bioclimatic strategies in the heavy laboratories sector

45.9

18.1

0

0.0

Heating

2. PASSIVE SOLAR HEATING The general SW-NE orientation of the building allows for

80.5

0.0

Cooling

Lights

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Fig. 4: Energy 10 simulation results showing the overall energy consumption of the proposed building compared with a reference one.


Results (Tab. 1 and fig. 4) suggest that daylighting improvement combined with the increased glazing thermal resistance and sun shading were the most determinant bioclimatic parameters for energy performance whereas the improved thermal resistance of the envelope had only a minor effect. However, advanced daylighting simulations proved to be essential to optimize the daylighting quality and quantity of the proposed skylights.

3. DAYLIGHTING The elongated L-shape of the building allows for the optimization of daylighting in all three sectors of the building: the teaching area (which includes classes, auditorium, offices and computer laboratories) as well as the light and heavy laboratories. Particular attention was given to the study of the heavy laboratory section of the building where thermal and lighting simulations of the extensive roof monitors were performed to optimize the daylight factor without penalizing the thermal performance. The size of the skylights had was determined early in the design process to respond to architectural and structural design needs using the Tregenza and Loe formula. The daylight factor formula soon needed to be converted into LUMcalcul (Demers et.al.), a sophisticated spreadsheet that has now been extensively used in subsequent applied research projects as well as professional training and teaching. The dimension of each skylight was also validated through preliminary experiments using PET and therefore fixed at 3m x 12 m, a size that could satisfy both thermal and lighting needs. Further analogical simulations in the artificial sky (fig. 5) and numerical simulations using ECOtect (2) and LUMcalcul (3) provided satisfactory daylight factor values in every occupied spaces.

Figure 6 presents some of the daylight factor results for three types of skylights that were simulated using physical modeling techniques in the artificial sky: the horizontal glazing (0°), and typologies using a vertical glass and a roof inclination of 30° and 45°. Photocells measurements were gathered at 15 locations of the typical floor plans on three longitudinal axis of the heavy laboratories to calculate the daylighting availability under an overcast sky, condition critical in 63% of the year in Canada (Demers, 2002). Three measurement locations were also added in the corridor leading to the laboratories. Those measurements were important to quantify the contribution of the skylights on the lighting of the corridor, and also confirm the relevancy of the proposed borrowed daylighting strategy using the lighting from the laboratories. The horizontal glazing obviously offered the best performance in the laboratories, with daylight factor values ranging from 5% to 15%. This option was however critical as it significantly increased the heating and cooling loads of the laboratories. It also provided great variations of lighting distribution that could contribute to certain risks of glare for users. The other vertical glazing options only averaged a 2% to 3,5% daylight factor and were therefore not considered satisfying for the task performed by the researchers. A compromised was reached with a 65° sloping glazing and a 30° roof slope (bottom right fig. 5) that still increased heating loads but decreased by 61% the lighting consumption.

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Fig. 5: Daylighting simulation in analogical artificial sky for a typical heavy laboratory

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configuration with vertical glass. They also qualitatively investigate the relative importance of the reflectance of certain walls in several configurations that were quantitatively convincing in preliminary experiments. White wall surfaces were thus recommended for the longitudinal walls of the laboratory as the lighting ambiance was much improved. Contrast levels between dark and bright daylight zones would also be less critical, thus reducing potential sources of glare in the space. The need to design the skylights with a greater view towards the sky was further investigated and a more refined version of the skylight was proposed. The 65° sloping glass typology was detailed and evaluated in the artificial sky. These later evolutions of the skylight typology, illustated in figure 5 at the right of the main model, also allowed to test variables relative to the material quality of the internal surfaces of the skylights such as:

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• curved versus a rectilinear surfaces • mirrored surfaces on the rectilinear surfaces • mate and glossy white surfaces Results showed that mirrored or curved surfaces did not considerably affect the internal illuminance distribution in the space. The rectilinear white configuration proposes a good daylight optimization that properly reflects towards the white sidewalls and deep into the space.

Axe Longitudinal

4. PASSIVE COOLING Fig. 6: Daylight factors as a function of skylight/roof geometry

Fig. 7: Daylighting distribution as a function of skylight geometry

Figure 7 shows the qualitative results obtained from the main simulations that occurred within the study of the initial three skylight typologies. The photographs show an interior view of the laboratory with different positioning of the skylight in relation to the sidewalls of the space. The photographs confirmed the fact that the space appears too dark and gloomy with the simulations that use the skylight

Heavy laboratories are naturally ventilated by a combination of cross and chimney effect strategies. The orientation of this section of the L-shape building takes advantage of the OSO-ENE dominant wind directions for cross ventilation whilst automatic low windows and high louvers located in the roof monitors allow for an effective extraction by chimney effect. Moreover, direct solar gains are controlled in summer by extensive fixed solar shading devices (fig. 8) throughout the building. Special attention to seasonal profile angles and snow accumulation potential led a custom shading device allowing maximum solar gains in winter and minimal gains in summer. Sun shading devices were also designed for the optimization of daylighting. They are made of translucent glass and oriented towards the sky to optimize the “sky view” from the interior space, in response to the critical overcast sky conditions that frequently occur in winter. On the western façade, the vertical position of the sunshades also favors reflections of light inside the building without causing any glare. Offices and public spaces are all provided with hybrid ventilation system where window operation automatically shuts off the HVAC distribution/return systems.


Modèle proposé 27nov - Performance Summary 750.7 168.8

600 400

64.3

30

64.3 0.0

14.11

20

214.2

517.6

200

$25.17

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10

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Annual Cost, $/m²

Annual Energy, kJ/m²

800

Other Lighting Cooling Heating

Fig. 9: Energy 10 simulation results showing the overall energy consumption of the proposed building compared with a reference one. Fig. 8: Extensive sun shading devices on the SW façade 5. ENERGY PERFORMANCE Figure 9 shows the final energy performance of the heavy laboratory section where the increased heating is compensated by the daylighting performance and absence of air-conditioning load.

CTBO - ANNUAL ENERGY USE Référence

Modèle proposé 27nov

240

The general design of the building aimed at a 25% energy consumption reduction compared to a standard reference building. The following strategies were combined with the passive solar heating, daylight and passive cooling contributions in order to reach a potential economy exceeding 32%: •

236.5

220 208.5

200

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180

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160 kWh / m²

143.7

140 128.8

120 100

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80 61.3

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46.9

46.4

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• Référence - Performance Summary $27.96 851.9

851.7

800

166.9

166.9

600

220.9

220.9

400

196.6

30

14.95

20

4.20 0.00

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0.0

200

463.9 8.81

267.5

0

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Consumption

Cost

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Annual Energy, kJ/m²

1000

•

Other Lighting Cooling Heating

• •

improvement of the thermal performance of the envelope and glass; variable frequency speed transmissions on the chemical hoods network and the de-dusting system; heat recovery loops in order to preheat the fresh air of the heating systems and to carry out the reheating of the air intake as well as peripheral heating; recycling of the air surplus of certain heavy laboratories in order to reuse it in other laboratories to compensate for the evacuated air; BMS (Building Management System) in order to optimize the overall performance of the mechanical systems; energy meters on the various networks of hot water and water vapor for heating vapor and cooled water for cooling in order to evaluate the energy consumption of the mechanical systems; photoelectric cells in order to maintain light intensity levels at the average illumination levels established by I.E.S., combined with presence detectors in all educational and administrative spaces; presence detector for HID fixtures with gradator for variable light intensity; artificial lighting system linked to the BMS for a complete sweeping of all lighting to optimize energy performance when the building non-occupied (evening, weekend, leave);


•

heating system conceived to recover the energy surpluses (low vapor pressure) possibly generated by a cooling power station to be built nearby.

6. EMBODIED ENERGY PERFORMANCE Environmental impact studies where carried out using the ATHENA environmental assessment software (5). Results shown in figure 10 suggest that an all-wood construction for the structure of the building (in comparison with a steel frame) allows a 40% reduction of the total primary energy use (embodied and construction) and an 85% reduction of the index of water pollution. An additional 25% reductions of air pollution and as well as a 25% reduction of the climate warming index demonstrated the important environmental advantage of the all-wood versus all-steel construction.

monitors and operable windows alone were perceived as non-feasible for snow accumulation/penetration reasons but after 2 years of full occupation, satisfaction proves high amongst occupants and managers. Daylighting availability in all spaces of the building represents a minimal 3% daylight factor value. In the working areas, daylighting meets the requirements for task lighting throughout the typical day occupation, which clearly exceeds the current LEED recommendations. The GRAP will soon conduct a post-occupancy evaluation of this building that has set the trend for future sustainable buildings on the Laval Campus.

8. ACKNOWLEDGMENTS The authors would like to thank Gauthier, Gallienne, Moisan Architects for their collaboration throughout the realization of this consultation as well as all the graduate students who took part in the numerous analogical and numerical simulations. The Kruger design team received a 2004 ConTECH mention in Sustainable Design for their IDP work.

9. REFERENCES 1.

Fig. 10: Compared embodied energy and environmental impact for wood and steel construction.

7. CONCLUSION The integration of the above passive environmental control strategies in Quebec’s cold climate has stirred important challenges for the University building services. Roof

Fig. 11: SW façade showing the black solar pre-heating system sections, SE oriented roof monitors, operable windows, and extensive SW sun-shading devices.

2. 3.

DEMERS, C., POTVIN, A. (2004), "LUMcalcul 2.01: prédiction de la lumière naturelle pour la conception architecturale", Proceedings of eSIM2004, Vancouver 9 -11 juin 2004. Demers, C MH, (2001), Daylighting availability in Quebec City, Canada. Internal report. POTVIN, A., DEMERS, C., BOIVIN, H. (2004), PETv4.2 Les profils d'équilibre thermique comme outil d'aide à la conception architecturale, Proceedings of eSIM2004, Vancouver 9 -11 juin 2004.