Modular construction's capacity to reduce embodied carbon emissions in California's housing sector

Abstract

Demand for new housing construction must be balanced with minimizing embodied greenhouse gas (GHG) emissions from building materials, logistical operations, and construction activities. This study examines the potential embodied GHG benefits that an innovative housing production method, factory-built modular construction, might have in meeting the multifamily housing needs, with California as a case study. A model is developed to quantify the embodied GHG emissions from materials, transportation, and construction for representative modular housing projects, contrasting results to scenarios where housing is constructed with conventional methods. Results are scaled from single building prototypes to meeting housing demand for lower income residents in California, representing 1.1 million housing units in all 58 of the state's counties. Statewide, compared to all housing units being stick-built, most modular types achieve emission reductions of 2–22%, with potential benefits depending upon structural framing material and factory location. A parametric sensitivity analysis reveals additional key modeling variables: module size and capacity of the module delivery vehicle. A Monte Carlo analysis is conducted for each county, comparing a random allocation of modular types from all factory locations to conventionally constructed housing. Counties farthest away from module factories experience GHG emission gains, while all other counties experience emission benefits of 1–14% (removing one of the modular types increases benefits to 4–20% for all counties). While the results are California-specific, the modeling framework is applicable to any location and relevant for regions assessing the embodied carbon impacts of rapid housing construction methods.