Page 84 - Zero Net Energy Case Study Buildings-Volume 3

CASE STUDY NO. 14 CALIFORNIA DMV FIELD OFFICE
(Below) Typical wall section. (Courtesy of SIM-PBK)
Building Envelope
The exterior walls predominently consist of a concrete masonry unit (CMU) structure sandwiched between metal panels on the exterior and a 2” layer of continuous insulation boards and a gyp- sum board finish on the interior. The attachment detail of the gypsum board layer allows thermal bridging to occur, so the wall only achieves a thermal resistance value of approximately R-5. The roof structure in general, however, has a much higher average level of thermal resistance, R-38, through more aggressive use of extra layers of insulation where space allows, which is important for a roof-dominated one-story structure in this climate.
The glazing is well-protected and is specified as low-e glass.
Daylighting and Electric Lighting
The daylighting roof monitor provides daylight for the main central space in the building, sub- stantially reducing electric energy demand during midday hours. The monitor actually faces northwest and, combined with the protected south clerestory windows, provides balanced and comfortable daylight distribution within that space.
Daylight and occupancy controls ensure efficient operation of the electrical lighting system, which consists entirely of LED light fixtures. Solar tubes were used for the lighting in all the cor- ridors, restrooms and storage rooms, which were easily worked around when the PV array was added to the roof during the construction phase.
Heating, Ventilating and Cooling Systems
The mechanical system uses standard package DX rooftop units, but with one advanced feature: air distribution is done via a raised floor approach. This allows the use of displacement ventila- tion for fresh air, where cool, fresh outside air is initially filtered and introduced at the floor level, slowly rising as it becomes warmed by occupant body heat. It is then exhausted directly out of the building without the need for an energy-consuming fan.
Night operation of the HVAC units is utilized during the swing season to use outside air to pre- cool the building in anticipation of the cooling demand later in the day.
Plug Load and Equipment
Where applicable, all equipment is EnergyStar rated.
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Zero Net Energy Case Study Buildings: Volume 3