Page 127 - Zero Net Energy Case Study Buildings-Volume 3

spring and fall seasons. Proximity to the ocean ordinarily would allow such an energy-conserving design strategy.
Heating, Ventilating and Cooling Systems
The laboratory spaces require an energy-intensive type of environmental control, primarily be- cause of the large use of fan energy to move air through those spaces. In the Science Building, these spaces are served by dedicated 100% outside air air-handling-units (AHU), which are equipped with energy recovery coils. This system is designed to maintain an air exchange rate in these spaces of 12 air-changes-per-hour (ACH) when occupied and 6 ACH when unoccupied, which is conventional practice in laboratory design. Variable air volume (VAV) boxes manage the air change rate in the spaces.
In the non-laboratory spaces, the HVAC system operates to maximize the use of natural ventila- tion for fresh air and space cooling when conditions permit. When air conditions require mechan- ical heating or cooling, the minimum required fresh air to the spaces is provided by the HVAC unit and the windows are closed. This combination of natural ventilation and mechanical heating/ cooling is known as mixed mode operation1.
The hot and chilled water supply to the HVAC units is piped to the building from the nearby Cen- tral Plant, which utilizes gas-fired boilers and absorption chillers. The energy use at the Central Plant for this purpose is also part of the total energy use of the building.
1
(Below) Central Plant Build- ing is located adjacent to the Science Building and provides heated and chilled water to the HVAC units located on the roof of the Science Building.
See also Case Study No. 10, West Berkeley Branch Library, in Zero Net Energy Case Study Buildings, Volume 2, p. 88.
LACCD HARBOR COLLEGE SCIENCE BUILDING
CASE STUDY NO. 16
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PHOTO: ETHAN ROHLOFF