ASHRAE LO-09-079-2009 Ventilation of Sustainable Schools Better than Traditional Schools 《可持续学校的通风设备 优于传统学校？》.pdf

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1、2009 ASHRAE 815SUMMARYDuring the last decades in the United Kingdom several educational buildings were built with a strong environmental ethos, real icons of a new generation of low-energy sustainable buildings. In some of the buildings post occupancy evaluations were held and buildings performance

2、was revealed. Also in the Netherlands during the last years several new concepts were developed for sustainable schools. This is an interesting topic as many of those schools had problems concerning energy efficiency, indoor air quality and thermal comfort. In the case of sustainable schools much ef

3、fort went into the design process of the schools to try to find better solutions to face the problems of the traditional designs. This resulted in different solution concepts, which raises the question which are better school concepts. From literature three evaluations from the UK and one overview o

4、f 5 sustainable educational buildings from the Netherlands are given, which show that sustainable educa-tional buildings are not always without flaws. In the paper two of the first Dutch sustainable elementary schools are compared with 9 more traditional schools of the Netherlands to conclude whethe

5、r the sustainable schools perform better than tradi-tional schools.INTRODUCTIONPresently sustainability becomes a necessity as effects of Global warming become more clearly. It is important to start early with the educational aspects of the necessary change in behavior and thinking, sustainable scho

6、ols could play an important role. The whole concept of a sustainable school building is based on principles of sustainable development which deal with the limited availability of natural resources, the interdependence with nature, the fundamentals aspects of interdependence with nature, the fundamen

7、tals aspects of production and consumption, and the issue of equity within, between and among generations 1.As the icon of a new generation of sustainable educational buildings which was completed in late 1993, the Queens Building at De Montfort University, Leicester, gained a repu-tation with its s

8、tartling architecture, in particular the distinc-tive ventilation chimneys 2, see Figure 1. The Queens Building was seen as the first in a new generation of low-energy, naturally ventilated sustainable buildings. Architect Short Ford Associates worked on the building design along-side environmental

9、engineer Max Fordham LLP, Cambridge Architectural Research (on the stack-effect chimneys) and Bristol University (on the physics of the airflow). The 10,000 m2building is L-shaped containing a complex arrangement of laboratories, classrooms and offices. The structure is almost exclusively naturally

10、ventilated 2.A detailed picture of the buildings performance was revealed in 1996, when a post-occupancy evaluation was carried out as part of the PROBE (Post-occupancy Review of Buildings and their Engineering) project. The assessment revealed a number of key shortcomings. Unresolved defects meant

11、that for the first two years the building operated with problems in critical mechanical and control systems 2. PROBE researchers found that the buildings design seemed to be effective at maintaining a comfortable environment, although the survey of its occupants, conducted by Building Use Studies (B

12、US), showed dissatisfaction with high summer-time temperatures and stuffiness in both winter and summer months 2.A revisit during early August 2006 revealed that some parts of the building have changed dramatically since the Ventilation of Sustainable Schools: Better than Traditional Schools?W. Zeil

13、er G. BoxemAssociate Member ASHRAEW. Zeiler is a professor and G. Boxem is an associate professor in Building Services in the Department of Architecture, Building and Planning, unit Building Physics and Systems, Technische Universiteit Eindhoven, Eindhoven, Netherlands.LO-09-079 2009, American Socie

14、ty of Heating, Refrigerating and Air-Conditioning Engineers, Inc. (www.ashrae.org). Published in ASHRAE Transactions 2009, vol. 115, part 2. For personal use only. Additional reproduction, distribution, or transmission in either print or digital form is not permitted without ASHRAEs prior written pe

15、rmission.816 ASHRAE TransactionsPROBE assessment, while others are much as they were when it took place. During the revisit an occupant survey was held and forty-five questionnaires were completed (compared with 75 in 1996). In general terms, satisfaction with temperatures in both summer and winter

16、is the same, although occupants perceive the air in winter to be better. Levels of satisfaction are very dependent on location. For example, the relatively high satisfaction rate for the refurbished offices is not matched by users in the new laboratories.In 1995, Hampshire County Council Architect S

17、ir Colin Stansfield-Smith designed a imaginative, low energy educa-tional building for Portsmouth University employing several environmental systems and ventilation strategies designed to deliver comfortable conditions and be of didactic value to the students. Externally, the building is a white-pai

18、nted rendered fortress 3, see Figure 2. Internally, it is light and bright, with white painted walls, windows and steelwork, complete with simple but good finishes. Five stair towers around the build-ings periphery act as natural ventilation air exhaust paths for the classrooms, studios and staff of

19、fices (with the exception of those on the top floor). The Portland Building was also inves-tigated by the PROBE Team 3.Questionnaires by 46 staff rated the building well as an all-rounder, coming just within the top 20% of the reference dataset, though people were happier with the aesthetics than wi

20、th comfort or functionality 3. There was however a good overall wintertime comfort, even though the building was judged to be hotter, stiller and stuffier than average. Summer comfort was judged average overall, but with a wide range of response and some people stated that is was significantly hot.

21、The building has good perceived air quality, in both winter and summer, besides some local problems 3. During the summer of 1997 an analysis of monitored air and slab temperatures was done by Kolokotroni et al. for the purpose of designing natu-rally ventilated educational building. From their analy

22、sis, they concluded that natural ventilation coupled with exposed ther-mal mass can reduce the effect of external hot weather and establish comfortable conditions within the building. It has also shown that if this moderating effect of thermal mass and natural ventilation is not controlled, unfavour

23、able internal Figure 1 Queens Building, De Montfort University 2.Figure 2 Portland Building 3.ASHRAE Transactions 817conditions can be established under certain external weather; in particular, cold spells during the summer 4. Since occu-pation the major changes have been a general increase in the u

24、se of computers, leading to occupancy and equipment densi-ties and heat gain and ventilation requirements beyond design expectations in some rooms. Lack of flexibility to cope with increased capacity is a weak point of the sustainable design concept.In the study of Sharples et al. 2007, Norfolk Comm

25、unity Primary School in Sheffield, UK, see Figure 3, built in 2005 with many sustainable features, was subjected to a post occu-pancy evaluation (POE) that involved both a social analysis and environmental monitoring. One of the key questions of the study was: did the school performing better enviro

26、nmentally than a standard school 5?The UK Governments Department for Education and Skills (DfES) Building Bulletin BB101 Ventilation of School Buildings recommends that for teaching and learning spaces between the start and finish of teaching on any day the average concentration of carbon dioxide sh

27、ould not exceed 1500 parts per million (ppm). In addition, BB101 recommends that for any occupied time, including teaching, the occupants should be able to lower the concentration of carbon dioxide to 1000 ppm. Figure 4 shows the mean CO2levels for the teach-ing and week-end periods, the dashed line

28、s show the 1500 ppm and 1000 ppm levels suggested in BB101.Figure 5 presents the indoor and outdoor air temperatures over a ten day winter period from Friday 17 February to Monday 27 February 2006. The dashed line in Figure 5 is the internal air temperature of 18.0C recommended in the School Premise

29、s Regulations and quoted in Building Bulletin 87 5.As can be seen from these three British examples sustain-able buildings are not flawless. So what is the situation in the Netherlands? Unfortunately there were only a few case studies done. Most important one was the evaluation of the first pilot pr

30、ojects of sustainable educational buildings. To show what is possible in practice with sustainable building design, the Dutch government sudsidized several pilot projects, from the 17 utility buildings there were 5 educational buildings: Van Hall Institute, Hogeschool Limburg, Educatorium, Peuterpa-

31、let and Scholencomplex Rijkerswoerd. The performance of these schools were monitored during a couple of years and presented in a overall study 6. The results are given in Figure 6. If we realize that normally the percentage of dissatisfied is between 10 to 20% we see clearly that some of the sustain

32、able schools perform on some aspects worst than traditional schools.In the Netherlands with respect to sustainable educational building the main focus has been on energy saving, leading to a reduction of 30% compared to the Dutch building regula-tions. This led to the application of hybrid ventilati

33、on: natural supply and mechanical exhaust ventilation. Within the Annex 35 Hybrid Ventilation in New and Retrofitted Buildings, an Figure 3 Norfolk Community Primary School in Sheffield, UK 4.Figure 4 Mean CO2levels for teaching and weekend hours 5.818 ASHRAE Transactionsinternational research proje

34、ct initiated by the IEA Implement-ing Agreement Energy Conservation in Buildings and Community Systems, the scope was to obtain better knowl-edge of the use of hybrid ventilation technologies 7. To avoid cross ventilation, each classroom has been equipped with a local ventilation system, that consis

35、ts of 2 electronically controlled inlet grills in the facade and a fan supported natural exhaust chimney. CO2sensors and temperature sensors auto-matically control the ventilation system. To meet the energy performance requirements the building has a high level of thermal insulation (U-values, the o

36、verall heat transfer coeffi-cient, of opaque parts 0.31 W/m2/K = 1,76 Btu/ft F h, U-value of windows 1.8 W/m2/K = 10,21 Btu/ft F h), good air tightness and energy efficient building services (high effi-ciency natural gas-boiler for heating and domestic hot water and high frequency lighting). The ext

37、ra 30% energy savings above the mandatory level of the building regulations are provided by the hybrid ventilation system (15%) and daylight sensors and a central sweep switch on the lighting system (15%).METHODOLOGYTwo sustainable designed schools were analyzed and the results compared with other m

38、ore traditional schools. To investigate the results of the sustainable schools measure-ments were done concerning thermal comfort and indoor air quality. During a week different measurements in schools were undertaken to be able to define the quality of indoor air quality and thermal comfort. Of the

39、 two sustainable schools, one school is the first sustainable elementary school of the Netherlands 1, the other school was part of the IEA (Inter-national Energy Agency) Annex 35 Hybrid ventilation project 7, so they are both relevant examples of sustainable designed schools as such.Indoor Air Quali

40、ty (IAQ) at schools is of special concern since children are extremely sensitive to results of poor air quality. IAQ in schools must reach the basic requirements and should be considered as a high priority because 8: (1) Child-ren more sensitive as they still developing physically and more likely to

41、 suffer from indoor pollutants, these growth processes are delicate and vulnerable to disruption, (2) Children are less well able than adults to metabolise and excrete most environ-mental toxins, (3) Children are relatively more heavily exposed to environmental toxins as they breathe higher volumes

42、of air relative to their body weights. Good air quality in classrooms supports childrens learning ability. Poor IAQ in schools influences the performance and attendance of students, primarily through health effects from indoor pollut-ants 9. Literature on relationships 10 between indoor air and envi

43、ronmental quality (IEQ) in class rooms and students health and academic performance has been reviewed 11. Carbon dioxide concentrations are often used as a substitute of the rate of outside supply air per occupant 12. IAQ in schools is primarily evaluated by CO2-concentrations. ASHRAE Standard 62-19

44、99 recommends an indoor CO2-concentration of less than 700 ppm above the outdoor concentration (1200 ppm) to satisfy comfort criteria with respect to human bio effluents. Dutch schools have to meet the Dutch Building Code (Bouwbesluit), which recommends a level of 1000 ppm CO2-concentration with a m

45、aximum of 1200 ppm.Figure 5 Mean internal/external temperatures for a ten day period 5.Figure 6 Evaluation results of aspect of the indoor climate of sustainable Dutch pilot projects 6.ASHRAE Transactions 819SchoolsBetween January 29th till March 31st 2004 measure-ments were conducted in 5 selected

46、schools. The measure-ments were conducted in alphabetical order from school A1 to E1, see Table 1 13.Between January 13th till February 22st 2005 the second series of long-term measurements were conducted in 6 new selected schools, see Table 2. Schools B2 and F2 are the sustainable designs 14.Measur

47、ementsOne classroom in each school building was selected for the measurements in the heating season during 1 week which include long-term measurements of air temperature, radiant temperature, relative humidity and air velocity. Equipment specifications used for those long-term measurements are shown

48、 in Table 3.QuestionnairesIn all schools, questionnaires were given to the teachers to get an impression of the satisfaction of the users, with regard to indoor air quality and thermal comfort. The questionnaires had questions about environmental perception and application of the system for the wint

49、er situation comprised: perceived thermal comfort, perception of indoor air quality etc.13The users have been asked to rate different aspects of the comfort. Distinction is made between summer and winter. Users opinion is the central point of this research. The ques-tionnaire used is based on the validated list which has been developed in the Health Optimisation Protocol for Energy-efficient Buildings research 15. The questions are based on a unipolar scale and should be interpreted as: 1 = very good 5 = una