Energy efficiency, indoor air quality, & health: a simulation study of multifamily housing in Boston, Massachusetts
Underhill, Lindsay Jeanne
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Residential energy efficiency is a major priority in the United States and abroad due to concerns related to climate change and the economic impacts of energy consumption. Energy retrofits can provide direct private and public savings as well as population health co-benefits as a result of reduced emissions from residential combustion and electricity generating units (EGUs). However, retrofits such as weatherization may also lead to reduced air exchange rates and accumulations of indoor-sourced pollutants. To protect indoor air quality (IAQ) and resident health, current building standards recommend coupling weatherization measures with ventilation; however, the combined impacts of these measures on energy costs, resident health, and general population health across diverse housing conditions have not been well-established. In this study, we used the multizone airflow and IAQ analysis program CONTAM to simulate the IAQ impacts of a real-world energy intervention in a specific low-income, low-rise multifamily housing complex. We evaluated the differential impact of indoor source activities, such as cooking and smoking, on indoor concentrations of PM2.5 and NO2. By co-simulating the CONTAM model with the energy simulation software EnergyPlus, we also examined the potential energy and IAQ trade-offs of meeting energy and ventilation building standards in a typical gas-heated midrise multifamily building. Lastly, we linked IAQ and energy simulation results from the midrise multifamily building to an energy-to-emissions model and health impact model to estimate the impacts of interventions on direct energy costs and monetized resident health and general population health. All building templates were located in Boston, MA. Overall, we found that combined investments in weatherization and ventilation retrofits could lead to energy savings and IAQ-related benefits; however, the direction and magnitude of benefits and/or disbenefits varied by intervention type and intensity, season, indoor source activity, and baseline ventilation parameters. Results suggest that some combinations of retrofits that provide energy savings may also lead to IAQ disbenefits for certain multifamily subpopulations, such as smokers in buildings without whole-building ventilation or filtration. We also found that weatherization interventions without ventilation upgrades led to increases in indoor PM2.5 levels and monetized resident health disbenefits that greatly outweighed direct energy savings and population health benefits. Together, results emphasize the importance of holistic energy-efficient interventions that explicitly consider IAQ and health. Our analytical framework can be utilized in future trade-off analyses to inform health-protective, cost-effective implementation approaches and building standards.