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1、SCIENCE CHINATechnological SciencesLow Energy Certificate An exploration on optimization and evaluation of energy-efficient building envelopeEnergy saving is the crucial task of green architecture, energy-saving design and evaluation should be interactive. Low Energy Certificate (LEC), an interactiv

2、e computer program for energy efficiency and certification of building envelope, is briefly in-troduced in this paper in aspects of certification standards, procedure, methods etc. Through the evaluation report of Innova-tion-pavilion PoI features, reference values of LEC are presented.optimization

3、and evaluation of energy efficiency, Low Energy Certificate (LEC), energy performance of building enve-lope, interactiveCitation:Zhang H, Leimer H P. Low Energy Certificate An exploration on optimization and evaluation of energy-efficient building envelope. Sci China Tech Sci, 2011, 54: 1639-1644, d

4、oi: 10.1007/s11431-011-4357-51 Actual design and evaluation of energy-efficient buildingsWhat is green building? Until now, there is still no world-wide uniform definition to it and individual evaluation sys-tem for energy-efficient buildings has its own emphasis. In Chinas Evaluation Standard for G

5、reen Building (GB/T 50378), “Green building refers to the buildings that can maximally save resources (energy, land, water and material), protect the environment, reduce pollution, provide healthy, comfortable and efficient use space as well as be harmoni-ous with the nature in the whole lifecycle.”

6、 The empha-ses are laid on resource-saving and environmental protec-tion. For the moment, there are several internationally rec-ognized green building evaluation or certification systems such as LEED (Leadership in Energy & Environmental De-sign, USA), BREEAM (Building Research EstablishmentEnvironm

7、ental Assessment Method, Britain), CASBEE (Comprehensive Assessment System for Building Envi-ronmental Efficiency, Japan), DGNB Certificate (Germany). Both Chinas Evaluation Standard for Green Building and US Green Building Councils LEED are comprehensive assessments which accentuate buildings impac

8、t on the en-vironment .In the current phase of green building development in China, the basic policy is to promote energy saving of buildings 3. Aiming at green building, energy efficiency is the problem that should be solved at first. On this aspect, it is often required that design and evaluation

9、could interact. To design energy-efficient buildings, the designers should be able to estimate/evaluate the building energy perfor-mance in the planning and scheme phase, so that to check the possibilities of energy saving according to the design scheme, to make appropriate adjustments betimes and t

10、o optimize the building energy performance.For the present, most evaluation or certification systems for green building list the building energy performance asone item that can be presented neither directly nor thor-oughly, and the interaction between design and evaluation is almost impossible. Furt

11、hermore, most green building evalu-ation systems cannot make necessary adjustments to refer-ence data corresponding to different climate conditions when the evaluated building is sited in other regions, so these systems have less flexibility and less applicability.Energy performance certificate for

12、buildings (Ener-gieausweis) issued by German Energy Agency (DENA) is for the moment the only one evaluation system especially aiming at buildings energy requirements. Energieausweis showing general building data certifies the energy quality of the building and provides a clear summary of the analysi

13、s results. It presents energy efficiency with a color scale which shows at a glance how much energy the building re-quires compared to other buildings. In China, up to now, there are two projects awarded Energieausweis, i.e. Pujiang office building in Shanghai and Cheng Kai Yu Yuan resi-dential buil

14、dings in Nanjing. The energy requirements rated by Energieausweis contain heating, hot water, lighting in-stallation, ventilation and cooling. According to different energy carriers (such as gas, electricity, renewable resource etc.), the fore parts of energy supply chain including energy exploratio

15、n, production, distribution and transition are measured with “preliminary energy consumption” so as to take resource preservation and environmental protection into consideration. Although Energieausweis presents the building energy quality comprehensively and directly, but as a European evaluation s

16、ystem, it cannot be directly adapted in China, since the regional climate conditions and political parameters are quite different. Furthermore, the calculation of Energieausweis is rather complicated and only the strictly trained, professional auditors with compre-hensive building-physical and HVAC

17、knowledge can make the calculation, which makes the interaction between design and evaluation more difficult.In fact, it is desirable for building designers to be able to use basic data to find out the crucial positions for the im-provement of building energy performance quickly and pre-cisely. Logi

18、cal, rational simplification of calculation and evaluation of building energy will help to realize the inter-action between design and evaluation.In this sense, Low Energy Certificate (LEC) made an in-structive exploration. LEC as a planning and controlling implement including a certification system

19、 is a simple, easy-to-use evaluation system with veracity and validity. Both architects and the approving authority with average knowledge could use LEC with an economically acceptable expenditure to understand and evaluate the energetic reac-tions of buildings. Excluding influences of equipments, e

20、n-ergy types and politics, and meanwhile taking the differ-ences of climate conditions into full consideration, LEC program can analyze the energy performance of the building envelope in virtue of basic building physical data, evaluate it and offer optimization suggestions.2 LEC an evaluation and op

21、timization pro-gram for energy efficiency of the building enve-lopeLEC is an interactive evaluation/optimization program for the building envelope. It can evaluate the energy efficiency of building envelope and building elements separately for the periods of heating, cooling and the whole year. The

22、evaluation results are marked with a simplified star system, and more stars mean the higher energy efficiency of the building envelope. In order to adapt to China, LEC program is integrated with the Chinese compulsory norm Design Standard for Energy Efficiency of Public Buildings (GB 50189-2005). (S

23、ee ref. 4 for more information).2.1 Basis and processes of the LEC-evaluation The calculations to evaluate the energetic quality of the building envelope are based on the results of build-ing-physical balance equation. According to Chinese com-pulsory norm Design Standard for Energy Efficiency of Pu

24、blic Buildings (GB 50189-2005), German norm DIN 4108-2, DIN 4108-6, and DIN V18599-2: 2007-02, LEC makes calculation under the consideration of the geometry, envelope construction, orientation, materials, building utili-zation, climate conditions etc. but excluding influences of HVAC equipments and

25、user behaviors.2.1.1 Evaluation standard for the heating periods For the heating periods, a reference building is defined con-sidering the geometry, the climatic region, orientation of azimuth and surface normal as well as the use that corre-spond to the evaluated building. As far as the building co

26、n-struction and elements are concerned, it complies with the Chinese Construction Standard of the 1980s, i.e. the stand-ard used before Building Energy Conservation Ordinance was issued.For the evaluation of heating, the end results of the heat losses (including loss of heat transmittance through th

27、e building envelope and ventilation heat losses) and the ther-mal heat gains for the heat period (including solar gain of heat and internal gain of heat) are summed up. The differ-ence between the annual thermal heating need of the exam-ined building and that of the reference building is the esti-ma

28、ted amount of energy saving used for evaluation (see Table 1).2.1.2 Evaluation standard for the cooling periods The heat protection in summer is supposed to achieve the comfort interior temperature without air-conditioning or the cooling energy need of usage-depending air-conditioned rooms is as low

29、 as possible. For non air-conditioned rooms, it should be guaranteed that the limiting value for the physi-ological beneficial internal temperature is not exceeded. TheTable 1 LEC-standard for winter periodsStandard for winter periodsReferring to the referencebuildingTable 2 Solar input valueS Solar

30、 input value= AG g FCA , glass proportion of facade1 Chinese building standard of the 1980s 2 3 4 2007 European standard5 2009 European building standard for low energy consumptionannual heating energy demand 71%annual heating energy demand 70%51% annual heating energy demand 50%31% annual heating e

31、nergy demand 30%21%annual heating energy demand 20%Gg , energy transfer coefficient of glassFC , shading coefficientTable 3 LEC-standard for summer periodsStandard for summerReferring to the reference buildingperiods1 cooling energy demand 170%2 cooling energy demand150%169 %comfort level for the su

32、mmer periods according to the Ger-man requirement of DIN 4108-2 is proved to be a practical base reflecting very well the scope of the climate that is just tolerable in the summer periods.The evaluation of the energetic reactions of buildings in summer is based on a process resulting from the requir

33、e-ments of the German norm DIN 4208-2 which were espe-cially adjusted to the climatic region of the world. The cri-terion “cooling energy neutral” defined for facades is de-scribed by interplay of the size of the window, the charac-teristics of the glazing as well as the sun protection, sun-blind an

34、d shading devices etc., which limits an exceeding of certain maximum temperatures to a few hours per year. Simply, a cooling-energy-neutral facade can make the room with no usage keep acceptable temperatures without cooling. Increased internal loads or the possibility of an increased ventilation to

35、lower the room air temperature are not con-sidered, since such dynamic heat exchanges have nothing to do with the energy quality of the building envelope.The hours of the internal temperature exceeding the lim-iting value and each climatic region with regard to each cooling period are used as criter

36、ia. With the help of a dy-namic thermal and energetic building simulation done by TRNSYS - a calculation program developed by the Solar Energy Laboratory of the University of Wisconsin-Madison, solar input values (see Table 2) are calculated as character-istic values of individual cooling-energy-neu

37、tral faades with different orientations in different climate regions and the results are taken as the basis of LEC-evaluation.For the evaluation of cooling periods, LEC compares the solar input value of the estimated building with that of the cooling-energy-neutral faades. LEC calculates cooling ene

38、rgy demand and cooling load per unit area, and then gives corresponding evaluation of the building envelope for cooling periods (see Table 3).2.1.3 Evaluation standard for the whole year After that the energy demand is calculated and estimated separately for the heating and cooling periods of each c

39、li-matic region, the energy demands for both heating and cool-ing will be summarized and identified within the framework of an overall estimation for the building (see Table 4). For3 cooling energy demand130%149 %4 cooling energy demand115%129%5 cooling energy demand2007/2009 European standard100%11

40、4 %this, both regional climate conditions and the duration of the heating or cooling period are considered.2.2 LEC evaluation procedure Following the menu, the users can input corresponding in-formation and data including basic project information, ref-erence climate, orientation, zoning, utilizatio

41、n, construction type, thermal transmittance etc. LEC calculates energy de-mand per unit area for the heating and cooling periods, and generates individual reports for building areas, building elements and windows as well as reports on energy perfor-mance rating.Reference climates: The maps of the co

42、untries are divid-ed into color-marked areas. The different colored overlaps represent the climate regions. Characteristics and divisions of the climate regions in China are based on the Chinese Norm GB 50189-2005. Climate zones - Hong Kong, Ma-cao and Taiwan were added as individual climate zones.

43、Once the reference climate is chosen, corresponding climate factors including the duration of heating or cooling periods will be given with diagrams and charts.Zoning: The more detailed the input of the zoning of the building, the more accurate the following energetic evalua-tion.Table 4 LEC evaluat

44、ion system by awarding starsLEC-standardExplanation1 The building does not correlate with any permit standard. 2 It corresponds to the minimum requirements according to GB 50189 3 It corresponds to the increased requirements according to GB/T 50378 4 It is comparable to the European building standar

45、d 5 It is comparable to an increased European building standard Utilization: according to the usage, there are three build-ing types, i.e. residential building area, office and /or busi-ness building area and others. For different utilization, dif-ferent boundary conditions will be chosen correspond

46、ingly during evaluation. For example, according to the standards, the limiting value of the interior temperature can be ex-ceeded temporarily, but not longer than 10% of the whole staying time. The staying time will be counted as 24 h per day in living rooms but only as 10 h per day in office rooms.

47、 In addition, there is a difference between the ventilation behaviors in these two different areas. Office buildings are ventilated more than houses but the ventilation intervals in houses are longer than in offices. Another reason to make a difference is because of the dissimilar internal thermal l

48、oads caused by technical devices and people, since the internal load referring to a short period in office building is much higher than that in houses.Construction type: lightweight construction and heavy construction. Lightweight construction refers to the build-ings with suspended ceiling, light partition walls, and cavi-ties under the roo