Page 127 - Designing for Zero Carbon-Volume 2_Case Studies of All-Electric Multifamily Residential Buildings

CASA ADELANTE AT 2060 FOLSOM CASE STUDY NO. 5 (Next page, Top)
Second-floor common deck.
(Next page, Bottom)
The shared courtyard on the ground floor.
Energy Performance and Operational Carbon: Post-Occupancy Measurement
Energy Use — Post-Occupancy Measurement
There are two electric utility meters recording energy use by the entire building. One meter spe- cifically records the energy use in the 126 apartments and the second meter measures the elec- tric energy use in the rest of the building areas. The energy produced by the solar PV system is separately metered and transmitted to the public utility grid. The building management company is responsible for all energy charges, which are determined from these three public utility meters.
Each apartment is locally metered for its energy use by the management company. The tenant pays for a portion of this with the monthly apartment rent charge, which is subsidized for an amount determined by formula for each tenant.
The actual electric energy used in the entire building, as measured by the two meters, is shown in the chart on the opposite page (top). The building consumed 926 MWh in the period of 9/2021 through 8/2022 and had an EUI = 18.6. The apartment meter recorded an annual energy use during that period of only 496 MWh—slightly more than half of the total building consumption— even though the apartments constitute more than 60% of the conditioned floor area.
Energy Production versus Energy Use
The aggregate total of energy used by all the apartment units on the project site is usefully compared to the on-site renewable energy generated by the solar PV system. This comparison is shown in the graph on the opposite page (bottom). The solar PV system provided 115,900 kWh during the period of 9/2021 - 8/2022. This total offset almost 25% of the energy used by the apartments during this same period, which was about 12% of the whole building’s energy use.
Post-Occupancy: Observations and Conclusions
The client team reported a challenge in negotiating some details of the energy costs associated with the energy supplier, Hetch Hetchy Power, which provides power to the City of San Francis- co, and the public utility, Pacific Gas and Electric Company (PG&E), which provides distribution services within the city boundaries.
The design team based the design approach for heating and cooling on the conventional as- sumption that the marine climate of San Francisco means space cooling can be accomplished by relying on unconditioned outside air. There is some concern that long-duration heat events due to climate change may require adjustment or modification of the apartment systems.
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