Page 29 - Designing for Zero Carbon - Case Studies of All-Electric Buildings

Thermal Storage – Phase Change Material
In order to reduce the peak cooling load that would normally result from the instantaneous solar heat gain created by the glass curtain wall (though a smaller peak due to the glass coatings) phase change material7 was added selectively to internal ceilings and walls, as well as to the pe- rimeter spandrel glass areas. The phase change material essentially absorbs the heat gain and then releases it at a later time, thereby lowering the peak and smoothing out the cooling load im- pact. Combined with the night flush operation, some of the heat gain never appears as a load on the cooling equipment. Another effect is that it extends the operating period of natural ventilation.
Daylighting and Electric Lighting
Good daylight penetration results from the narrow floor plates, approximately 56 feet wide. Re- duced glare from the glass curtain wall on the east and west facades due to the frit pattern ap- plied to the glass enhances the visual comfort level of the interior spaces.
All electric lighting is LED-sourced, with occupancy sensors and 50% dimming capability.
Natural Ventilation
As indicated in the wall-section and the typical curtain wall elevation, there are large operable windows located at two heights on each floor, one at occupant level and a second one just below the ceiling. This occurs at the long east and west elevations along the entire length of the build- ing, producing ample fresh air flow via this optimal cross-ventilation design.
The upper windows are automatically controlled by the building management system (BMS) and the lower windows are user-operated, allowing each person to choose personal comfort conditions. If outdoor air temperature conditions warrant natural ventilation, then the BMS opens the upper windows and the cooling system is shut off. If cooling is required, then the upper win- dows automatically close. For the meeting rooms, the cooling system cannot operate unless the manually-operated lower windows are closed, as signaled by window contacts. However, for the open-plan office areas, the cooling system can operate if some of the manually-operated lower windows are still open; occupant training was deemed to be sufficient to create awareness of this condition and to learn to follow the action of the automatic upper windows.
When the night flush operation is engaged, the upper windows open and the operation proceeds, usually with natural air flows. The mild marine climate of Santa Monica is benign enough for the natural ventilation mode to proceed for most of the year. In the winter, a short pre-heat period is sometimes required in the mornings.
Heating, Ventilating and Cooling Systems
The HVAC system utilizes air-source heat pumps to generate heated or chilled water that cir- culates through radiant concrete slabs. These concrete slabs are completely exposed on the underside and partially exposed on the floor above, thus heating or cooling the spaces above and below through radiant means. During peak cooling events, the radiant slab cooling is supple- mented by three separate VAV air-handling units (AHUs) for active cooling requirements in the three major zones.
A separate VRF (variable refrigerant flow) system is used only for electrical and server rooms (cooling only). Exhaust air from these rooms is circulated back into the office spaces as needed for heating in the winter months.
Domestic hot water (DHW) is provided by residential-type air source heat pumps.
7 ENRG BlanketTM by Phase Change Solutions, https://phasechange.com/enrgblanket/ Designing for Zero Carbon: Volume 1
(Above) Phase change mate- rial installed over insulation in selective walls. (Courtesy of Buro Happold.)
SANTA MONICA CITY HALL EAST
CASE STUDY NO. 1
(Following Page) Interior view of typical office space, with courtyard beyond the windows at right. (Photo: Jeremy Bitter- man.)
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