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Home energy retrofits, or weatherization improvements, improved IAQ by remediating existing hazards such as lead or radon, reducing air exchange with outdoor air and lowering outdoor pollutant levels indoors, removing pollutant sources such as water leaks and unvented heaters, and adding functional ventilation and/or filtration (Figure 1). On the other hand, weatherization worsened IAQ by disturbing legacy pollutants such as lead or asbestos, reducing ventilation, leading to an increase in indoor pollutants, introducing new formaldehyde-emitting construction materials, and failing to install mechanical venting when it was needed or installing unreliable systems.

Figure 1. A weatherized building is protected from the outside elements to maximize energy efficiency.

A strong team of researchers at the University of Colorado, led by Dr. Shelly L. Miller (¾«Æ·SMÔÚÏßӰƬ Mechanical Engineering), conducted a 3-year study funded by the U.S. EPA to evaluate weatherization improvements used to adapt homes in low-income communities to a changing climate against empirical evidence of respiratory health effects and measurements of indoor air quality (IAQ) and ventilation rates. We recruited at least 250 homes over the next 1.5 years.

In 125 single-family homes that had undergone weatherization improvements and 125 single-family homes that had not been weatherized, we assessed, through a combination of questionnaires, lung function testing, household walkthroughs, and blower door testing, the home characteristics and respiratory health of the residents. Lung function was documented with forced expiratory volume in 1 second (FEV1) and forced vital capacity (FVC) measurements. Weatherized and non-weatherized homes were selected in neighborhood pairs, and non-weatherized homes were screened using the income-eligibility requirements of the weatherization programs.

On a subset of 30 homes (15 weatherized and 15 not weatherized), we continued assessment during prolonged wildfires to explore impacts on IAQ. In the subset of homes, we measured temperature, relative humidity, carbon monoxide, carbon dioxide, formaldehyde, and particulate matter both indoors and outdoors of the homes during and after wildfires. Home ventilation rates were estimated using a model linking weather data and leakage area.

The outputs of this work included quantitative data on housing characteristics, respiratory health, and IAQ during wildfires for low-income residents who had received energy retrofits to reduce their energy use. This information was crucial to understand how weatherization affected health and indoor air quality. We determined from this study how wildfires impacted the IAQ in weatherized homes. We used outcomes from this study to provide guidance on weatherization that reduced energy use in homes while still providing a healthy indoor environment.

Investigators: Shelly L. Miller, PhD (PI), ¾«Æ·SMÔÚÏßӰƬ; shelly.miller@colorado.edu; Elisabeth Root, PhD, Ohio State University; John Adgate, PhD, and Elizabeth Carlton, PhD, CU Denver Anschutz Medical Campus, Colorado School of Public Health

Publications

Humphrey, J.L., Barton, K.E., Shrestha, P.M., Carlton, E.J., Newman, L.S., Root, E.D., Adgate, J.L. and Miller, S.L., 2020. Air infiltration in low-income, urban homes and its relationship to lung function.ÌýJournal of Exposure Science & Environmental Epidemiology, 30(2): 262-270.Ìý

Carlton, E.J., Barton, K., Shrestha, P.M., Humphrey, J., Newman, L.S., Adgate, J.L., Root, E. and Miller, S.L. Relationships between home ventilation rates and respiratory health in the Colorado Home Energy Efficiency and Respiratory Health (CHEER) study.ÌýEnvironmental Research, 169:297-307, 2019,Ìý

Humphrey, J.L., Lindstrom, M., Barton, K.E., Shrestha, P.M., Carlton, E.J., Adgate, J.L., Miller, S.L. and Root, E.D. Social and Environmental Neighborhood Typologies and Lung Function in a Low-Income, Urban Population,ÌýInternational Journal of Environmental Research and Public Health, 16:1133, 2019,Ìý

Shrestha, P.M., Humphrey, J.L., Barton, K.E., Carlton, E.J., Adgate, J.L., Root, E.D. and Miller, S.L. Impact of Low-Income Home Energy Efficiency Retrofits on Building Air Tightness and Healthy Home Indicators,ÌýSustainability, 11:2667, 2019,Ìý

Shrestha, P.M., Humphrey, J.L., Carlton, E.J., Adgate, J.L., Barton, K.E., Root, E.D. and Miller, S.L. Impact of Outdoor Air Pollution on Indoor Air Quality in Low-Income Homes during Wildfire Seasons.ÌýInternational Journal of Environmental Research and Public Health,Ìý16(19), p.3535, 2019,Ìý