Page 126 - Zero Net Energy Case Study Buildings-Volume 3

CASE STUDY NO. 16
LACCD HARBOR COLLEGE SCIENCE BUILDING
Daylighting and Electric Lighting
Daylight modeling of program spaces was carried out using RadianceIES software and the re- sults were factored into the whole building model. Electric lights are controlled in the spaces by daylight sensors and occupancy sensors, as well as pre-programmed light level requirements.
Natural Ventilation
Natural ventilation can be used only in the non-laboratory spaces. The original design strategy utilized automatic window operation controlled by the BMS (Building Management System) ac- cording to a sequence of operations based on outside and inside air temperatures and data from CO2 sensors in the occupied spaces. But it was decided by the facilities director that main- tenance requirements for this design approach would be relatively demanding for a reduced number of staff, and therefore it would not provide dependable operation over time. The design team therefore opted for user control of the windows, with a visible “red light - green light” system mounted in a prominent location in the spaces to signal when windows can be opened (or not) to establish comfort conditions.
Such user control has drawbacks (see the discussion in the section Post-Occupancy), but the system operation is designed to minimize them as much as possible. The occupants get a “green light” signaling that the windows can be opened when the inside air temperature is 70°-75°F, the outside air temperature is 55°-75°F and the CO2 sensor measures 900 ppm or less. The “red light” is switched on if the inside or outside air temperatures are outside that respective range, or if the CO2 sensor measures 1100 ppm no matter what the temperature. In the latter case, which potentially occurs only in the large lecture rooms under special conditions, the HVAC system can operate to provide enough fresh air to reduce the CO2 level once the windows are closed (presumably as directed by the instructor in the larger spaces).
The switch to user-control of the operable windows also eliminated the possibility of using a cool air “night flushing” operation of the natural ventilation system to pre-cool the building during the
(Below) Interior of classroom with large windows that allow natural ventilation via manual operation by the occupants.
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Zero Net Energy Case Study Buildings: Volume 3
PHOTO: TOM BONNER