Modeling and Analyzing Distributed Heat Pump Domestic Water Heating in Modular Multifamily Buildings

Victor Braciszewski
Stet Sanborn
Justin Tholen
Harshana Thimmanna
SmithGroup

Tyler Pullen
Carol Galante
University of California, Berkeley
Terner Center for Housing Innovation

Jamie Hiteshew
Factory_OS

The University of California (UC), Berkeley, Terner Center for Housing Innovation; SmithGroup; and Factory_OS examined the integration of a distributed 120-volt, shared circuit heat pump domestic water heating system in multifamily modular construction. The research team focused on hot water systems because of the high proportion of building energy used for water heating in multifamily apartment buildings in the United States (EIA, 2015); the distributed system focus was chosen for its potential to simplify standardized installation within volumetric modular housing construction practices. The study focused on two primary factors: (1) the energy performance of the distributed heat pump system relative to centralized natural gas and heat pump domestic water heating systems, and (2) the installation cost comparison between a centralized versus distributed heat pump domestic water heating system using modular construction methods. The energy modeling and analysis revealed that centralized heat pump domestic water heating systems in multifamily housing projects could offer 29-percent energy savings compared with traditional, natural gas-fired systems; furthermore, distributed heat pump water heater systems can save an additional 3 percent in energy use compared with centralized equivalents. Built using offsite modular construction techniques, the distributed heat pump hot water system adds an anticipated $1,800 in per-unit installation costs compared with centralized systems without factoring in rebates and incentive programs. In-factory installation also provides potential benefits not captured in this estimate, including faster installation times and higher quality control to minimize onsite rework and maintenance (a common issue with traditional onsite installation), alongside electricity savings throughout a project’s life cycle.