Template of Manuscripts for IREE

International Review of Mechanical Engineering (I.RE.M.E.), Vol. 3, n. 6

Energy Savings and Carbon Reduction due to Renovated Buildings Hasim Altan1, Jitka Mohelnikova2

Abstract – The paper deals with an energy saving case study of a renovated building in comparison with the building energy balance before renovation. The renovation was carried out in the building envelopes such as external walls, floor on ground and the flat roof for the improvement of thermal insulation properties of the investigated building. The renovation has brought forward energy saving effects, which are important for both reducing energy consumption for heating during winter seasons and the associated heating costs. In addition, the renovation represents a positive environmental impact due to the reduction of carbon dioxide emissions from such dwellings. The energy renovation of the case study building evaluated was used as a base for an estimation of energy savings and reductions of carbon emissions within a housing estate residential complex with twenty similar buildings. The study presents the importance of having such thermally insulated building envelopes in building together with windows that also have good thermal property and insulation quality for the reduction of overall energy consumption. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved. Keywords: Energy Savings, Buildings Retrofit, Thermal Insulation, Heat Losses, Sustainable Buildings

I.

Introduction

Building envelopes of many residential buildings do not satisfy strict demands for energy savings. An energy renovation of existing buildings requires many design tasks [1] but the major importance is focused on additional thermal insulation of the building envelopes and window retrofitting [2]. Improvements through the building envelopes [3] energy renovation can bring important reduction of energy consumption for winter heating seasons and carbon dioxide emissions caused by dwellings [4], [5], [6]. Energy saving requirements brought demands for further reductions of heat consumption in buildings [7]. The article presents results of assessments which were focused on a renovation of selected types of buildings and their evaluation from the energy efficiency point of view. Buildings in a housings estate have been investigated. These buildings and their envelopes do not satisfy strict demands for energy savings. As a result, these existing buildings were to be renovated. The renovation of buildings both designed and completed in accordance with the above mentioned process and as a result this could significantly reduce the heat losses and diminish the heat consumption in such buildings. The energy renovation could also help to bring extra improvements to the indoor environmental conditions such as thermal comfort.

Manuscript received January 2009, revised January 2009

II.

Buildings for energy Renovation

The energy renovation was designed and practically carried out for the selected buildings [8] of a housing estate in Brno (see Figure 1). The energy evaluation and the assessment of building envelopes of the investigated buildings was carried out in order to evaluate the reduction of heat consumption for space heating due to better thermal insulation properties of windows, peripheral walls and roofs and floors of basements and ground floors.

Fig. 1. The housing estate (Brno) with the investigated buildings

Copyright © 2007 Praise Worthy Prize S.r.l. - All rights reserved

H. Altan, M. Mohelnikova

II.1.

Investigated Buildings

The panel-block buildings with nine storey; eight overground floors (residential part) and a ground floor (entrance and service part) was investigated. The structural height of individual floors equals 2.85 m, building floor area is 353.16 m2 with a total building volume of 9058.6 m3. Peripheral walls were constructed of prefabricated reinforced concrete panels. The building envelope does not satisfy present thermal insulation requirements. For this reason the additional thermal insulation of foam polystyrene was applied (thickness of 150 mm). Obsolete windows with wooden frames and two separated glass panes (overall heat loss coefficient of the window was U=2.70 Wm-2K-1) were replaced by new ones with plastic frames and double glazed units with low emissivity glazing and argon filling (U=1.40 Wm-2K-1). The following figure shows two main representatives of the selected building. The first building is in an initial state with current conditions and the second one is after renovation, see Figure 2. Better thermal properties of new windows and a facade with additional thermal insulation significantly reducing heat consumption. It is obvious from the figure that the insulated facade has lower external surface temperature compare to the envelope of the initial building. This practically means that the reduction of heat losses during a winter heating season.

Fig. 2. Photographs of the selected building before and after renovation

Peripheral panels faced problems with internal surface condensation and mould growth mainly in corner positions before the renovation. Thermal resistance of the panel (reinforced concrete block with lightweight concrete core) equals to value R=0.42 m2KW-1. Overall heat loss coefficient of the panel is U=1.7 Wm-2K-1 (determined for surface heat loss coefficients; on the interior side hi=8m2KW-1 and on the exterior side he=25m2KW-1). The computer simulations have proven that the temperature in corners is less than 10.7°C. This temperature is lower than the dew point temperature which is a characteristic for indoor environmental conditions (design indoor temperature 20°C, design indoor relative humidity 50%). Temperature in the corner between the two panels with an additional thermal insulation is measured about 15°C. This means that the building envelope renovation could eliminate the condensation problems. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved

II.2.

Thermal Insulation Improvements

The design of the investigated building envelope renovation was carried out for constructions exposed to indoor and outdoor boundary conditions (design values) as they are noted in Table 1. TABLE 1 BUILDING ENVELOPE CONSTRUCTIONS AND AMBIENT TEMPERATURES Design indoor Design outdoor Construction Area [m2] Temperature Temperature External walls 1293.12 (over ground part) 21.0 °C Facade windows 407.04 -12.0 °C (over ground part) Walls (basement) 198.68 Small windows 15.0 °C 13.84 (basement) Floor on ground 353.16 +5.0 °C Flat roof 353.16 21.0 °C -12.0 °C

Heat transfer losses of the above mentioned building constructions were determined for the studied building (in the initial state 144.76 kW and renovated state 40.26 kW). Reduction of heat transfer losses is more than 104.5 kW after the building envelope renovation (calculated for the design boundary conditions) - see Table 2. TABLE 2 DETERMINATION OF HEAT TRANSFER LOSSES FOR THE INITIAL AND RENOVATED BUILDING U-value of Constructions Heat Losses initial renovated initial renovated Construction [W m-2 K-1] [W m-2 K-1] [kW] [kW] Walls I (over ground 1.7 0.25 72.54 10.67 part) Windows (over ground 2.7 1.4 36.27 18.81 part) Walls (basement) 1.7 0.25 9.12 1.34 Windows 2.7 1.4 1.01 0.52 (basement) Floor on ground 1.7 1.7 6.0 6.0 Roof The whole Building

1.8 Average U-value 2.05

0.24 Average U-vale 0.87

19.81 Total Losses 144.76

2.91 Total Losses 40.26

III. Energy Balance The energy balance of the investigated building (before and after renovation) was calculated [6] for the given climatic conditions. Solar gains were determined on the basis of average monthly values of energy of global solar radiation [kWh.m-2] for North, South, East and West oriented vertical planes (see Table 3) [9]. These values were selected for evaluation of energy balance during a typical heating season between October and April.

International Review of Mechanical Engineering, Vol. 3, n. 6


TABLE 3 CLIMATIC DATA USED FOR THE ENERGY BALANCE CALCULATIONS Global solar radiation [kWhm-2] Design affecting the building facade Month outdoor temperature South North West/East October 9.3 71.57 10.36 32.33 November 3.3 41.07 5.52 15.87 December -0.3 30.95 4.03 11.18 January -1.5 41.94 5.21 15.01 February -0.2 53.31 7.26 22.21 March 1.9 89.73 15.60 48.89 April 8.5 88.42 24.04 65.84

The energy balance was determined for the reference heating season (between October and April). The following figures compare total heat losses and gains of the investigated building in the initial state (see Figure 3) and after the renovation (see Figure 4). Total heat losses consist of heat transfer and ventilation losses [10]; total heat gains were determined of internal heat gains and solar gains; it was evaluated in computer program Energy [11].

The renovated building represents a significant reduction of heat consumption for space heating. Energy savings resulting from the retrofit and also annual specific heat consumption relative to the building volume which is also presented in Table 4. Energy savings bring also reduction of carbon dioxide emissions. The table shows result of the study aimed at the determination of reduction of CO2 emissions due to energy savings and lower heat consumption - calculated for gas heating (54 kg CO2 per GJ [12]). The housing estate with twenty renovated residential buildings could help to bring important energy savings for the heating demands 109.55 TJ during five heating seasons. These savings could again help to reduce carbon dioxide emissions about 6000 tonnes. It practically means that the energy efficiency renovation of housing estates could help to bring positive ecological effects. TABLE 4 TOTAL HEAT CONSUMPTIONS AND ENERGY SAVINGS Heat consumption of per the heating season Initial State

Renovated building

Total Heat Consumption

1533.7 GJ

438.24 GJ

1095.48 GJ

CO2 Emissions per 1 building

82.82 t

23.67 t

CO2 Emission Reduction 59.2 t

CO2 Emissions per 20 buildings

1656,4 t

437,4 t

CO2 Emission Reduction 1219 t

350 Ql [GJ]

Qg [GJ]

Heat lossess and gains [GJ]

300 250 200 150 100

IV.

50 0 October November December

January

February

March

April

Months of the reference heating season

Fig. 3. Energy balance of the building, initial state Ql…total heat transfer and ventilation losses Qg…total internal heat gains and solar gains 140 Ql [GJ]

Qg [GJ]

120 Heat losses and gains [GJ]

Energy Savings

Building

100 80 60 40 20 0 October November December January

February

March

April

Months of the reference heating season

Fig. 4. Energy balance of the renovated building Ql…total heat transfer and ventilation losses Qg…total internal heat gains and solar gains


Conclusion

The results of the assessment of the investigated buildings have shown that the energy aimed at retrofitting building envelopes represents important reduction of energy consumption for space heating. The presented energy renovation study has shown that building envelopes could play significant role in energy savings in residential buildings. Sufficient thermal insulation properties of peripheral walls and windows with double glazed units and insulated frames together with a roof of a high thermal insulation quality and properly insulated floor on ground could bring high energy efficiency. Many renovations in buildings are not necessarily efficient in spite of energy saving improvements due to the lack of energy rating concept. The complete energy renovation of buildings should consist of many tasks. One of the main tasks includes putting in a heating control system in buildings and monitoring of the heat consumption in individual flats and service rooms. Window retrofit is also a necessary measure for energy efficiency improvements due to the inconvenient properties of existing glazing and window frames. The additional thermal insulation of building envelopes such as facades, roofs and floors on ground are usually completed after a window retrofitting. In addition to the



main renovation tasks subsidiary improvements were recommended as the additional glazing of loggias and balconies. The glazed external parts created buffer zones which limited the heat losses and extended the utilization area of individual flats. When renovating such existing residential buildings, considering the installation of new and energy efficient HVAC systems, and even the use of solar collectors or heat pump technologies could significantly improve the building standard and further reduce the overall energy consumption. The above mentioned renovation tasks could bring significant energy savings for winter heating costs as well as for reduction of carbon dioxide emissions from such dwellings.

Acknowledgements The energy evaluations were carried out within the frame of the research project GACR 101/05/H018, “Development of effective systems for improvement of indoor climate comfort in buildings” and project GACR 101/09/H050 "Research of Energy-Efficient Systems and Installations for Indoor Climate Comfort". The presented paper was completed under the UK-CZ collaborative programme of the Building Environments Analysis Unit (BEAU) Research Centre of the University of Sheffield.

References [1]

I.C. Ward, Energy and Environmental Issues for Practicing Architects, (London: Thomas Telford Limited, 2004, ISBN 0 7277 3216 1, 7-22). [2] S.I. Gustafsson, B.G. Karlsson, Window Retrofits and Life-Cycle Costing, Applied Energy, Vol. 39, pp. 21-29, 1991. [3] W.P. Spence, Construction-Materials, Methods and Techniques, (New York: Delmar Publishers, 1998, ISBN 0-314-20537-3, 694705). [4] M. Bell, R. Lowe, Building Regulation and Sustainable Housing. Part 3: Setting and Implementing Standards, Structural Survey, Vol. 19, No. 1, pp. 27-37, 2001. [5] R.J. Lowe, Defining and Meeting the Carbon Constraints of the Twenty-first Century, Building Research and Information, Vol. 28, No. 3, pp. 159-175, 2000. [6] http://www.ucl.ac.uk/carb/ [7] Ward, I. What are the energy and power consumption patterns of different types of built environment? Energy Policy, Vol. 36, pp 4622-4629, 2008. [8] Energy Audit of Panel-block Buildings (Obla14, Brno), Brno University of Technology, 2003. [9] Standard EN 832 Thermal Performance of Buildings-Calculation of Energy Use for Heating Residential Buildings, 1998/AC: 2000. [10] Standard ČSN 73 0542 Method of Estimation of Energy Balance of Glazed Area in External Building Structures, 1995. [11] BRE Assessment Procedure for Energy Rating of Dwellings, 2001 Edition. [12] Svoboda Z. Computer Program Energy, CVUT Prague, 2005.


Authors’ Information 1

Hasim Altan. School of Architecture, The University of Sheffield, United Kingdom Tel: +44(0)1142220375, Email: [email protected] 2 Jitka Mohelnikova. Faculty of Civil Engineering, Brno University of Technology, Veveri 95, 602 00 Brno, Czech Republic Tel: +42(0)541147420, Email: [email protected] Dr. Hasim Altan is Architect-Lecturer and Director of the Building Environments Analysis Unit (BEAU) Research Centre in the School of Architecture at the University of Sheffield, UK. He has been promoting Energy Efficiency in Buildings and providing Environmental Design and Sustainability advice and resources to the building industry in related areas as part of Knowledge Transfer Partnership/Network (KTP/N). Dr. Altan’s previous research focused on the drivers and barriers to improving energy efficiency and reducing carbon dioxide emissions in the private housing sector, where he investigated energy efficiency standards of 250 privately rented properties in Sheffield including energy performance ratings and carbon dioxide emissions. He has worked extensively on energy efficiency strategies for domestic buildings and is also part of a research project consortium of Carbon Reduction in Buildings (CaRB) which is a socio-technical, longitudinal study of carbon use in buildings in the UK. CaRB is a major research project funded by the Engineering Physical Sciences Research Council (EPSRC) and Carbon Trust as part of Carbon Vision Buildings (CVB) research programme (October 2004 - July 2009). Dr. Altan’s current research activities are in the areas related to Energy Efficient and Sustainable Building Design, Environmental Modelling and Building Performance Simulation, Post Occupancy Evaluation (POE) of Building Energy Use and Environments including Daylighting, Indoor Air Quality (IAQ) and Thermal Comfort studies. Dr. Altan has published over 40 papers in journals and conference proceedings as well as carrying out book reviews. He is currently running two masters programmes in Sustainable Architecture at Sheffield University as well as an External Advisor for ‘Low Carbon Building Design’ masters course at University of Salford, UK. He is on the peer review panel of 4 major international journals. He is also Cofounder and Board member of IBPSA-England - the English regional affiliate of the world-wide acting International Building Performance Simulation Association as well as of Chartered Institution of Building Services Engineers (CIBSE) Building Simulation Group (BSG) in the UK with the intention to inform and promote best practice in using computer simulation codes for building related applications, to improve the accuracy of predicting their performance in practice with the aim of designing comfortable and healthier buildings with optimum energy efficiency. Assoc. Prof. Jitka Mohelnikova is Lecturer of Brno University of Technology, External Consultant of the Building Environments Analysis Unit (BEAU) Research Centre of the University of Sheffield, UK.

Participant of Projects: - GACR 101/05/H018 "Research of Efficient systems for Indoor Climate Comfort" - MSMT CZ-102 "Research of Real Annual Daylight Conditions for Effective Utilisation of Light-Guides" - MSMT MEB 080804 "Angular transmittance of tubular light guide diffusers" - LLP project "Education and Training on Renewable Energy Systems for Housing (ETRESH)" - GACR 101/09/H050 "Research of Energy-Efficient Systems and Installations for Indoor Climate Comfort"
