The Thermal Test and Analysis of Envelope in Existing Buildings

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1 The Thermal Test and Analysis of Enveloe in Existing Buildings Xiaoyan Liu Xiaoqing Li Jiangang Sun Zhen Wang Professor Graduate Professor Professor Civil Engineering College of Daqing Petroleum Institute, Daqing, Abstract: This aer deals with the roject to imrove existing building energy efficiency. Building energy efficiency is an international toic that includes many asects. There are more than 43 billion square meters of existing buildings in China, so how to imrove the health and comfort and minimize the energy consumtion costs of existing buildings is quite imortant. Imroving existing buildings can be divided into two arts, enveloe and heating system. Much research has been done on building conservation during the ast 30 years in China. The structure of enveloes is imroved, and many new energy efficiency materials are used in buildings while some other foreign researchers have develoed several kinds of software for the analysis of building energy conservation. In this aer, we reort on the results of heat transfer loss tests in existing buildings in Daqing, including the walls, doors, windows and the floors. The areas with most heat loss areas are ointed out, and the objective of reducing the heat cost is discussed. The design for imroving the structure of existing buildings for reduced energy consumtion costs was rovided. The energy consumtion cost in existing buildings can be reduced by u to 30% through these imrovements. ey words:thermal test; analysis; envelo 1 INTRODUCTION The erformance of building envelo is reflected by the energy costs, thermal comfort, and air quality of building. In order to get the result of the energy costs, thermal test is necessary. Major requirements that influence building envelo erformance include: control of heat flow, control of air flow, control of water vaor flow, control of rain enetration, control of light, solar and other radiation effects, control of noise, control of fire, rovision of strength and rigidity, durability, and aesthetics [1].The environmental chamber is the first of its kind in Canada and is unique in concet. It is located in a secially constructed laboratory of the Centre for Building Studies (CBS), in downtown Montreal []. Fiber-reinforced lastic(frp) materials are being more frequently used in building construction. A testing rogram was develoed to investigate the thermal characteristics of a tongue-groove fiberglass comosite anel system [3]. Otherwise, some test such as fire resistance of walls and floors in Jaan [4], the test for effect of moisture on hygrothermal and energy erformance of a building in Poland [5] are both carried out. In this aer,we have found out the main heat loss art of a existing building, and we have also given out the rebuilt design advice. The heat loss were both analyzed before and after rebuilt. THERMAL TEST PROCESS We have tested the temerature on the surface both inside and outside the building. The heat transfer loss has also been tested. 17 reresentative temerature-tested oint was disosed, and 8 heat flux-tested oint was also disosed. The test lasted 5 days [6]. The temerature inside and outside the buildings, and the temerature on the surface of the buildings, and the heat transfer loss through the buildings envelo (including the walls, doors, windows beams and the floors) have all been tested. Three reresentative house on different floors (the first floors, the standard floors and the to floors) were chosen for testing. The number is , , The temerature sensor for testing is T-tye thermoelectric coule, and the heat transfer sensor is WYP, WYP1, and WYR heat transfer flake. There are

2 98 temerature-tested oints and 70 heat flux-tested oints.. Test rocess The test last for 15 days. The data were recorded every 5 minutes, and more than 1,00,000 were collected. According to these data, we could conclude the change trend of the data along with time. Then the heat transfer coefficient and heat cost could be calculated. It could hel us to analysis the otential caability of energy conservation and design the energy conservation rogram. 3 THE RESULT AND ANALYSIS OF THERMAL TEST 3.1 The Average Temerature of Each Points According to the data, take (1 day) as an examle. Fig1 is the temerature inside and outside south living room and on the surface of south wall both outside and inside. According to the curve in Fig. 1, we could conclude that the temerature inside living room and on the surface inside the wall is stable, while the trend of the temerature outside living room and on the surface outside the wall is like a sine wave. 3. The Average Temerature Per Day Both inside and outside the Building during the Test. According to the data, the temerature changes from 13.5 to 1.7,only the temerature of kitchen and hall is below 16, others is above 16. So the temerature could almost meet the require of the standard. 3.3 The Heat Transfer Coefficient of Various of Envelo Heat loss, temerature inside and outside the building, heat transfer coefficient and thermal resistance are calculated and the result is in Tab. 1. Average heat transfer coefficient of the wall could be calculated by equation 1 F + B1 FB 1 + B FB + B3 FB3 m = (1) F + F + F + F m B1 Average heat transfer coefficient of the exterior wall, W /( m ) ; Average heat transfer coefficient of the main exterior wall body, W /( m ) ; B1 B B3 Heat transfer coefficient of the thermal bridge on exterior walls, W /( m ). F Area of the main exterior wall body, m ; F B1 FB FB3 Area of the thermal bridge on exterior walls, m B B3 Fig. 1 Temerature inside and outside south living room and on the both surface of south exterior wall.

3 Tab. 1 The heat transfer arameter of various of building envelo Temeratur Suface Suface Air temerature Heat Heat transfer e inside temerature temerature outside flux coefficient inside wall outside wall South wall of living room Beam of south wall in living room East wall of east Beam of east windows in east North wall of north Beam of north windows in north door North balcony door South windows of living room North windows East windows Living room floors North floors East floors The heat transfer coefficient of envelo in the standard are shown in Tab. [7].According to the standard, the heat transfer coefficient of the existing buildings has oversteed the limit of standard. The heat transfer coefficient of the roof has oversteed 174%, the wall s has oversteed 140%, the windows have oversteed 30%, and the floor has oversteed 173%. Comared to the energy conservation buildings, in order to kee the temerature inside above 16, it needs more energy. Most of the energy lost through the envelo. It s a serious waste of energy. So it s in dire need of energy conservation rebuilt for these existing buildings. 4 REBUILT PROJECT The rebuilt roject is add a iece of olystyrene slab to the envelo of existing buildings (roof, wall and floor). The thickness of olystyrene slab is in Tab.3.

4 The temerature and the heat flux distributing of wall are shown in Fig. and Fig.3. Tab. The heat transfer coefficient limit of building envelo in Daqing osition arameter roofs exterior walls windows doors floors heat transfer coefficient, W/(m ) Tab.3 The thickness of olystyrene slab on envelo arameter heat transfer coefficient of heat transfer coefficient of thickness of olystyrene osition buildings, W/(m ) standard, W/(m ) slab, mm roofs walls floors Fig. The temerature distributing of wall

5 Fig3. The heat flux distributing of wall 5 CONCLUSIONS Through the thermal testing, calculation and (1) The heat transfer coefficient of the existing buildings has oversteed the limit of standard. The heat transfer coefficient of the roof has oversteed 174%, the wall s has oversteed 140%, the windows have oversteed 30%, and the floor has oversteed 173%. () The thermal resistance of the walls is 0.80(m /W), the thermal resistance of the roofs is 0.73(m /W), both of them haven t get the minimum thermal resistance of standard. The roof is more serious. The thermal resistance of the roofs is only 83% of the minimum thermal resistance. It s easy to dew on the surface of envelo, and it will influence the erformance of envelo. (3) The heat cost of the buildings (take 3-1 as an examle) is W. While 8.8% is the heat transfer cost, it s W. The roof thermal energy cost is 13.9%. The wall s is 6.9%. The artition walls of staircase is 7.4%. The door s is 1.3%. The windows is 1.9%. The floor is 8.6%. Air enetrate thermal energy cost is6750.3w, it s 1.7%. (4) The building heat cost index is 46.3W/m, but the limit of building heat cost index in Daqing is analysis of existing buildings, we have given out these conclusions. W/m. So it has serious oversteed the limit. (5) In order to reduce the heat cost index to the limit, a iece of olystyrene slab is added to the envelo of existing buildings (roof, wall and floor). The thickness roof, wall and floor is 57mm, 51mm and 95mm. REFERENCES [1] Hutcheon, N.B. Requirements for exterior wall.[j] Canadian Building Digest, Vol. 48, Nat. Res.Council, Div. of Build. Res. Canada, [] Paul Fazio, Member, ASCE, Andreas. Athienitis, Cedric Marsh, Jiwu Rao. Environmental Chamber for Investigation of Building Envelo Performance [J].Journal of Architectural Engineering/June, 1997, [3] Ossama A. Abdou. Thermal Performance of an Interlocking Fiber-Reinforced Plastic Building Envelo System. [J]Journal of Architectural Engineering/March, 1997, [4] Y. Sakumoto,T. Hirakawa, H. Masuda,. Nakamura Fire Resistance of Walls and Floors Using Light-Gauge Steel Shaes[J]. Journal of Structural

6 Engineering/November, 003, [5] Dariusz J. Gawin, D.Sc. Marcin oniorczyk, Aldona Wieckowska, Ph.D. Elisabeth ossecka, D.Sc. [6] Wang Zhen, Liu Xiaoyan, Zhang Yongyi, Cai Yingwei, Gong Haiying Otimization of energy conservation design of constructional enclosing Effect of Moisture on Hygrothermal and Energy construction[j] Journal of Daqing Petroleum Performance of a Building with Cellular Concrete Walls in Climatic Conditions of Poland. [J] ASHRAE Transactions, 004, Institute 001, 5 (1):95~97(In Chinese) [7] Energy conservation design standard for new heating residential buildings JG9 6 95(In Chinese)