Home energy retrofits, or weatherization improvements, can improve IAQ by remediating existing hazards such as lead or radon, reducing air exchange with outdoor air lowering outdoor pollutant levels indoors, removing pollutant sources such as water leaks and unvented heaters, and by adding functional ventilation and/or filtration (Figure 1). On the other hand, weatherization can worsen 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 is needed or installing unreliable systems.

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

A strong team of researchers at the University of Colorado led by Dr. Shelly L. Miller (CU Boulder Mechanical Engineering) is conducting a 3-y 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 (project website). We are recruiting (see Figure 2) at least 250 homes over the next 1.5 years.

Figure 2. Recruiting Homes to our Study.

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

Figure 3. Engineering Team Conducting a Blower Door Test.

On a subset of 30 homes (15 weatherized, and 15 not weatherized), we will continue assessment during prolonged wildfires to explore impacts on IAQ. In the subset of homes, we will measure 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 will be estimated using a model linking weather data and leakage area.

The outputs of this work are quantitative data on housing characteristics, respiratory health, and IAQ during wildfires for low-income residents who have received energy retrofits to reduce their energy use. This information is crucial to understand how weatherization effects health and indoor air quality. We will also determine from this study how wildfires impact the IAQ in weatherized homes. We will use outcomes of this study to provide guidance on weatherization that reduces energy use in homes while still providing a healthy indoor environment.

Investigators: Shelly L. Miller, PhD (PI), CU Boulder; 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