Simulation of indoor and outdoor air quality and health impacts following installation of energy-efficient retrofits in a multifamily housing unit

Efforts to reduce energy consumption and greenhouse gas emissions in the United States have led to widespread interest in energy-efficient retrofits in the residential sector. Weatherization retrofits, such as air sealing and insulation, lower residential energy consumption, resulting in reduced fuel and electricity-related emissions, improved ambient air quality, and avoided climate and health impacts. However, retrofits without adequate ventilation may worsen indoor air quality (IAQ) and lead to adverse health effects and costs that offset anticipated economic benefits. Building energy management and climate action plans often omit these potential consequences. This study presents a novel framework that quantifies health and energy costs and benefits related to residential energy-efficient retrofits. Energy savings from reduced consumption were estimated using historical energy prices. Reductions in ambient emissions of fine particulate matter (PM_2.5) precursors were translated to avoided health impacts using health damage functions. Indoor PM_2.5-related health impacts were estimated by applying PM_2.5 concentration-response functions to changes in IAQ. Health impacts were monetized using health impact assessment techniques and compared to retrofit-related savings. For a modeled gas-heated midrise multifamily building in Boston, MA, weatherization retrofits without ventilation or filtration retrofits led to household health costs that far exceeded energy savings and population-level health savings, given increases in indoor PM_2.5 concentrations (3.1 μg/m³ and 20.4 μg/m³ for standard and high-performance retrofits, respectively). In contrast, weatherization coupled with ventilation and filtration retrofits resulted in large savings. Overall, this study reinforces the need to quantify residential health impacts in assessments of energy-efficient retrofits.