Getting to All-Electric Multifamily ZNE Construction (2016-2021)

The goals of this California Energy Commission funded project were to demonstrate the technical and economic potential for optimized zero net energy (ZNE) construction practices in new multifamily buildings to inform best practices, codes and standards, and to communicate lessons learned to facilitate broader adoption of ZNE practices with reduced performance risk. 

Four sites were studied: Sonoma and Napa County wine country (Cloverdale and Calistoga), the San Francisco Bay Area (Sunnyvale), and the central coast (Atascadero). All four sites are fully electric, LEED Platinum, 19-24% above code when originally modeled, have a zero net energy sized solar array, have Energy Star appliances, have heat pump water heaters, have R19-21+R5 walls, and have R38-49 attics. The four sites were monitored with second-by-second energy and one-minute interval water usage with a total of 208 residences with (a) individual heat pump water heaters, (b) central heat pump water heaters, and (c) central combined heat pump system. Circuit-level monitoring equipment installed in each apartment allowed the team to develop a picture of tenants’ electrical usage. Each unit was also equipped with a lighting display (Nexi) that provided real-time feedback of energy use to tenants. In addition, utility data, tenant surveys, and detailed DHW monitoring (tank temperatures, pump power) was collected.

The insights from this project led the research team to support the 2019 and 2022 code cycles, particularly the 2022 all-electric proposal. The project successfully demonstrated that comfortable, efficient, all-electric affordable multifamily is possible, even in 2014 when some of the sites were constructed.

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