Horizontal louvres in the glazed cavity normally used for HVAC applications were adapted to provide adjustable solar control. There are 12 aluminium louvres for each floor, spanning the full distance of 4.5 metres between columns at verti-cal spacings of 200mm. Motorized screw shaft rods provide the power drive for each segment to respond to ambient sunlight conditions. During the occupied daytime period, the louvres track the sun, virtually eliminating solar heat gain in the occupied zone, whilst still allowing the penetration of diffuse daylight. Each Intelligent skins
166 Case studies
building face is fitted with two photocell sensors which when shaded stop the movement of the louvre, i.e. when the photocell is in shade, the angle of the lou-vre is sufficient to shade the interior of the building. The loulou-vres were designed to be fully adjustable between the horizontal position and 45° for full shade.
Controls
The computerized building management system (BMS) includes facilities for security, alarm and fire alarm systems as well as energy management of the HVAC system. It has control over dampers, fans, chillers, boilers and air han-dling units. The perimeter lighting system and louvres are also controlled by the BMS to respond to ambient daylight levels. When heat is not required in the double skin cavity, time- and temperature-activated sensors will operate vent-ing dampers at the top and bottom of the cavity, releasvent-ing the convective warm air at the top.
Sensors were placed inside the concrete slabs at many points around the build-ing perimeter so that data about the thermal performance of the buildbuild-ing could be monitored and analysed on a continuing basis. The system was fully equipped with data collection capabilities to provide information on energy usage patterns throughout the building.
User control
Wall-mounted switches within each of the corner offices (approximately 10%) can locally override the position of the louvres. The remainder of the louvres are always under automatic control. Temperature control thermostats are under occupant control.
Operating modes
In summer and winter, the operable louvres in the glazed cavity are automati-cally adjusted to prevent direct solar radiation from entering the building by means of a photocell controller.
At night and during other unoccupied hours, the louvres are closed for increased insulation, retaining the conditioned air from daytime operation.
Performance
Due to corporate policies, no actual energy use or monitoring information has been released to the design team. An independent analysis of the design was conducted by Dr Vladimir Bazjanac from the University of California, Berkeley.
He developed a computerized model of the building’s energy performance, by applying mathematical values to those variables that affect energy consump-tion. Evaluations were performed that analysed the demands for heating, cool-ing, lighting and occupant-operated equipment. The study found that the predominant energy characteristic of the building was the louvred double skin, which optimized energy performance. The building was found to maintain unique energy demand stability, particularly when compared to a conventional office design. At the time of completion, it was believed to be the most energy-effi-cient building in its particular climatic zone.
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Daylight adjustment – reflection/protection ■ Glare control – blinds/louvres/fixed ■ ■ Responsive artificial lighting control ■
Heating control ■ ■
Heat recovery – warmth/cooling ■
Cooling control ■
Ventilation control ■
Fabric control – windows/dampers/doors ■
Insulation – night/solar ■
Passive Manual Automatic
Poor quality circuit boards for the louvre control system were changed in 1984.
The operating team for the building has taken to blocking off the cavity vents at top and bottom with plywood boards to minimize winter air infiltration.
Delivered energy consumption
The target energy consumption for the building was set at a maximum of 55,000 Btu/ft2/yr (174kWh/m2per year) during the design phase. Three alternative schemes were developed, each representing a different response to the energy conservation objectives and cost/benefit performance. The dynamic skin concept proved the most energy efficient, and was selected as the preferred solution. The energy performance of this design was calculated at 39,000Btu/ft2/yr (123kWh/m2per year). Figures as low as 33,000Btu/ft2/yr (104kWh/m2per year) have been quoted for the predicted consumption rates.
Design process
Computer based simulations of predicted energy use were performed for each of the three alternative schemes. A variety of computer tools were used by the energy consultants, Burt Hill Kosar Rittelman Associates, to determine heat-ing and coolheat-ing requirements and solar shadheat-ing. Additional energy analysis was performed at University of California Berkeley, using the DOE-2 program and TRY weather data for nearby Buffalo. The heating load was estimated at 2%
of that for a conventional building and cooling loads 19% of normal.
The calculations were confirmed with mock-ups of the double skin. A full-scale mock-up of one module of the double skin design was erected in Tempe at the College of Architecture, Arizona State University. It was instrumented and test-ed by Professor John Yellott to determine the skin’s shading coefficient, U-val-ues and light transmission characteristics. The mock-up demonstrated that a substantial airflow was induced by chimney action when the outer glazing and the louvres were heated by solar radiation.
Intelligent skins
Annual energy use 104kWh/m2*
Typical energy use for building type 316kWh/m2
Annual CO2output n/a
Number of sensors 16
Visited by authors ✔
Monitored by others ✘
*Estimated during design phase (actual figures not available due to corporate policies).
Credits
Client: Hooker Chemicals and Plastics Corporation (now Occiden-tal Chemical Corporation), Dallas
Architects: Cannon Design Inc, Grand Island, NY
Early planning: Hellmuth Obata & Kassabaum (consulting architects) M/E: Cannon Design Inc, Grand Island, NY
Energy Consultants: Professor John Yellott (Phoenix, AZ), Profes-sor Richard S Levine (Lexington, KY), Burt Hill Kosar Rittelman Associates (Cambridge, MA)
Structural: Gillum Consulting Engineers
General Contractor: Siegfried-Scrufari Joint venture
References
Architecture, March 1989, Vol 78, No 3
Architecture d’Aujourd Hui, December 1980, No212 At the Rainbow’s End, Anon
The Building Systems Integration Handbook, Richard D Dush (Ed), Wiley, Chichester, NY 1986
Glass in Architecture, Michael Wigginton, Phaidon, 1996 Marketing Material provided by Cannon Design Inc Progressive Architecture, 4:80
Progressive Architecture, 4:83
Mark Mendell/Frank Smaak/Millard Berry, Cannon Design Inc Mr Victor Snyder, Occidental Chemical Corporation