Page 81 - Zero Net Energy Case Study Homes-Volume 2

SILVER STAR APARTMENTS
CASE STUDY NO. 9
Phase change material8 is placed inside the south wall to reduce the indoor temperature swing and to provide some passive heating in winter evenings by delaying the daytime heat gain. The phase change material is estimated to reduce the seasonal heating and cooling loads by 30%.
Windows are manufactured, vinyl-framed, double-glazed with a low-e coating. The assembly is R-3 and has a solar heat gain coefficient (SHGC) = 0.25.
Building Envelope — Airtightness
Airtightness was designed and built into the exterior wall and roofs of three buildings using a continuous air barrier, as well as gasket and sealant products, as listed as approved by the Cali- fornia Energy Commission9. LEED for Homes (low-rise) and Energy Star® requirements are met through HERS-verified air sealing and insulation installation inspections. These inspections con- firmed that the building’ envelopes of all three structures meet QII (Quality Insulation Installation) HERS performance specifications for air-sealing as required by the California energy code10.
A Blower Door was not performed on the project. (Tests have shown that California code require- ments result in an airtightness of approximately 5 ACH50.)
Heating, Ventilating and Cooling Systems
A 3⁄4-ton ducted mini-split system is installed in each unit and the manager’s office. Larger units serve each of the manager’s apartment and the large community room. These systems are rated at SEER-19 (seasonal energy efficiency ratio). The condenser units for each are located on the roof.
Ceiling fans are installed in the major rooms of each apartment to increase occupant comfort at higher indoor air temperatures and thereby reduce the use of the mini-split systems.
Lighting and Plug Loads
LED lighting was specified throughout the project. In addition, the daylight levels were raised in
the unit by creating a higher floor-to-floor height. This allowed the windows to be taller than nor-
mal, which gave deeper penetration of daylight to the unit interior. The advanced framing method
allowed the window headers to be placed even higher, therefore further increasing the daylight
penetration. The overall effect is to increase the likelihood that the occupant will not reflexively

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use the electric lights because of the ample amount of daylight in the unit.
Control Systems

Standard thermostats are used to control air temperature in each unit and the separate common
areas. Other than basic light switches, there are no other user-controls or automatic controls such as occupancy sensors. No system is in place for monitoring the energy use of the individual units. One utility meter measures the net energy use for the entire complex.
8 A. Wilson, “Storing Heat in Walls with Phase Change Materials”, Green Building Advisor, (Nov., 2009), https://www.greenbuildingadvisor.com/article/storing-heat-in-walls-with-phase- change-materials; See also: M. Reynolds, “Phase Change Building Materials – Natural Heat Storage in Buildings”, Ecohome, (Jan., 2017), https://www.ecohome.net/guides/2205/phase- change-building-materials-natural-heat-storage-in-buildings/
9 https://ww2.energy.ca.gov/HERS/documents/QII_Air_Sealing.pdf 10 Ibid
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