Page 62 - Zero Net Energy Case Study Buildings-Volume 1

CASE STUDY NO. 3
IDeAs OFFICE BUILDING
Interior Lighting
Installed interior light fixtures using T8 lamps were state-of-the-art energy-efficient light fixtures in 2007, when the building was completed and ready for occupancy. The fixtures were supplied with dimming systems activated by daylight sensors in the space and which dimmed the lights continuously in response to available daylight.
As part of using the building to evaluate different types of fixtures, several different types of high efficiency fixtures with dimming capability were specified. With one type, the dimming system is controlled at the electric panel with control software loaded on to a specific computer in the office. The latter allowed users to modify the lighting schedule as desired for more efficient operation of the lights. A second type of fixture had the dimming controls built into the fixture itself rather than a programmable device at the panel. Each of these types of approach to dimming in response to daylight availability resulted in issues that had to be resolved during the post-occupancy period; these will be discussed in a later section of this case study.
Heating, Cooling and Ventilation
The HVAC system consists of a ground-source heat pump system with a hydronic radiant floor system in a concrete floor slab, with natural ventilation and a back-up fan-driven fresh air ventila- tion system. The ground-source heat pump piping is a horizontal coil installation in the area to the east of the building, which was originally part of the shopping center parking lot. (Diagram below.) The hot water for the radiant floor system when used for heating is supplied by a solar thermal system; the heat pump acts as a backup and maintains the hot water temperature in the system thermal storage tank. The chilled water for the radiant floor when used for cooling is made by the heat pump, with the heat dumped into the ground via the coil installation.
The backup fresh-air ventilation system has a supply fan only. A general building exhaust fan was determined to be unnecessary because of the small size of the building and the inherent “leakiness” of the building envelope.
The system operates in a type of “mixed mode” design. When outdoor air temperatures are com- fortable, the fan does not operate and natural ventilation via occupant control of the windows is used. The intermediate condition, when outdoor air temperatures are still comfortable but inter- nal loads create a need for a small amount of cooling, the occupants are expected to operate the windows to provide the needed cooling.
PHOTO: DAVID WAKELY
(Opposite and below) Energy system diagrams. (Courtesy of Integral Group).
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Zero Net Energy Case Study Buildings: Volume 1