Observations on the Design, Implementation, and Performance of Low-energy Public Buildings. Daniel Feuermann

Transcription

1 Observations on the Design, Implementation, and Performance of Low-energy Public Buildings Daniel Feuermann Department of Solar Energy and Environmental Physics, Jacob Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Sede Boqer Campus 84990, Israel

2 Outline Background: location, climate Projects: design & implementation Small office building Student dormitories Conclusions and recommendation

3 background The scene: Location: Negev high lands, elevation 475 m, Satellite campus of Ben-Gurion University Climate: Summer: Hot days cool nights Ambient avg. temperature: 25 o +-7 o C Winter: Mild days cold nights Ambient avg. temperature: 10 o +-5 o C There is a four month heating season

4 background The cast: Architect Consultant Local administration Administration overseeing construction and budget Contractor Maintenance department Occupants

5 Projects (1) Office building for academic staff (2) Dormitories for the School for Desert Studies background Common design philosophy: The buildings should use the winter sun for heating (direct gain), and night-ventilation for cooling in the summer, minimizing the need for air conditioning. Pre-requisite is good insulation and high thermal mass for energy storage. Local experience single family dwellings as well as modeling show that passive solar heating can provide 60 to 80% of winter heating, and air-conditioning is not absolutely necessary when using night-ventilation.

6 1 st Project: Office building Design Winter day Ca. 20 offices, seminar room, library, facilities. Solar heat: ~60% Offices: conventional A/C; direct solar gain with control Lobby: desert cooler & night ventilation; direct solar gain

7 Winter operation Design Almost all offices are heated via direct gain windows. In addition, offices are individually heated via fan coil units which have a built-in heating element. A lecture hall and a few offices are heated by conventional air conditioning. The atrium/lobby is heated only passively via the large clerestory (upper) windows: Philosophy: The atrium/lobby does not need to be perfectly thermostated.

8 Direct solar gain in the lobby/atrium Design

9 Summer operation Design Offices: fan coils provide cooling via the central chiller unit. Shading is provided by overhangs, plus external blinds/shutters. Central Atrium: it is cooled via the desert cooler during the day, Turned off if exit temperature of desert cooler exceeds temperature indoors. At night the water pump is stopped and the desert cooler works dry, when outside temperature is lower than inside.

10 implementation Summer day: note no exterior blinds

11 Planned were exterior retractable blinds Administration decides: Instead exterior use interior venetion blinds. implementation Result: poor solar control, overheating in the transition season when sun is low in the sky and heating is not necessary

12 Desert cooler: ca. 20 air changes per hour. Reduce necessary installed cooling capacity by about 1/3. implementation

13 implementation Cool air outlet: air flows freely between acoustic ceiling and concrete ceiling/floor.

14 Administration/construction-supervision decides on cheapest device, ignores need for soft water or proper bleeding (and drain pipes). Result: After initially working properly, the lobby is now far too hot in summer: Desert cooler is not working properly: clogged mats; salt accumulation destroy pumps frequently (every six weeks), replacement is slow. Maintenance: thermostat not working, controls for smoke-relieve (in case of fire) conflict with windows for night ventilation and evaporative cooling. Maintenance crew lacks expertise to deal with the problems. implementation

15 2 nd Project: Dormitories design Lay-out ensures solar rights; East-West orientation with sufficient distance between rows Orientation due south degrees with little loss in solar gain Hot water: central solar water heating for entire neighborhood

16 Winter operation: Direct gain shutters for night time insulation. Passive solar heating (60-75%), small electric heaters for backup. design Summer operation: Fan-assisted, thermostat-controlled night ventilation; Solar control via external shutters for all windows. Students receive a pamphlet with explanations. General: Well insulated, good quality windows.

17 Student schedule is different from the average family: implementation Closed shutters at 9:30 am, Jan 19

18 Closed shutters at mid-day in January Note that solar rights are maintained.

19 implementation Example housing unit with open shutters

20 implementation Night-ventilation: no thermostat was installed; lower-cost but noisy axial fan instead of impeller fan. Poor solution for sealing the exhaust duct in winter, results in high infiltration.

21 Exhaust-fan control mechanism implementation Ceiling fan for comfort

22 implementation

23 Observations (and from talking to students). Students do not open shutters until late in the day due to work-habits. Students leaving for the weekend close shutters; thanks to the large thermal mass, the building takes days to warm up again (by means of solar or otherwise) Some students (particularly foreign students) keep shutters closed when not in the room due to perceived safety problems. Some students (Israeli) must keep windows open because they don t get enough air

24 Location of central solar hot water facility; Administration decides late into the project to cancel the system in favor of individual solar collectors. Reason: apparent cost-savings implementation

25 Collectors are mounted at 20 slope because of esthetics at the price of lower efficiency, particularly in the winter. Collectors are not visible from street level. implementation After students complain, collector tilts are corrected with consequences

26 Observations: Administration did not fully understand the functioning of the building, nor the importance of details of the climate-adapted design. conclusion Mid-stream changes dictated by the administration causes major changes in the functioning and even the esthetics of the building negating the original design. Architect and consultant did not appreciate the behavior of the students different from families. Maintenance department not sufficiently trained in maintaining non-standard items.

27 consultant(s) architect administration (virtual client) Insufficient communication before and during construction conclusion contractor administration (purse strings) construction department maintenance dept. real client

28 Suggested communication paths before and during construction consultant(s) maintenance dept. contractor architect administration (virtual client) administration (purse strings) construction department real client suggestion: perform workshops that include consultant, architect, administration and construction/ maintenance departments already during the planning stage. recommendation

29 In conclusions: Study the real client s behavior. Do not rely on participation of inhabitants for building performance: the system has to work independently. Educate administration by means of workshops, especially the administration that is responsible for overseeing construction and budget. Make sure maintenance personnel understand the functions of all elements and can maintain it. conclusion