More than 7 million US homes have received energy efficiency improvements since the start of the Weatherization Assistance Program in 1976, which provides grants to states, territories, and some Indian tribes to improve the energy efficiency of the homes of low-income families. These improvements include heating and cooling upgrades, improved insulation, air sealing, caulking, weather-stripping to doors and windows, and window replacement. Weatherized households are now seeing $250-$480 annually in energy savings. Homes that are weatherized under federal programs are required to have added ventilation if the home becomes too tight.
Home energy retrofits, also called weatherization, can improve indoor environmental quality (IEQ) by remediating existing hazards such as lead or mold, reducing air exchange with outdoor air (lowering outdoor pollutant levels indoors), removing pollutant sources such as unvented heaters, and by adding functional ventilation and/or filtration (IOM 2011; Nazaroff 2013). On the other hand, weatherization may worsen IEQ by disturbing legacy pollutants such as lead or asbestos, increasing air tightness leading to an increase in indoor pollutants, introducing new formaldehyde-emitting construction materials, and failing to install mechanical venting when it is needed.
Low-income communities are disproportionately exposed to poor indoor and outdoor air quality as well as hazardous housing conditions (Bahir 2002; Houston et al. 2004; Krieger et al. 2002; Litt et al. 2010) Rates of asthma, including incidence and asthma morbidity are higher in low-income populations (IOM 2000). While low-income populations may have the most to gain financially from reduced heating and cooling bills that weatherization can provide, they may also be most vulnerable to adverse health effects.
Indoor air quality studies of weatherized residential buildings have shown that some pollutant levels increase, while others decrease. A study by Noris et al. (2013) conducted energy retrofits on 16 low-income multifamily apartments that were designed to save energy and improve IEQ. Particulate levels, carbon dioxide, and volatile organic compounds generally improved whereas formaldehyde and nitrogen dioxide varied by building. Larger decreases in indoor sourced pollutants were realized with larger increases in ventilation rate and IEQ improved more in buildings with added mechanical ventilation (excluding particles).
The picture is similar for indoor radon. The main factors that drive radon levels in homes are radon concentrations in the soil gas around the home (high in Colorado, which is in zone 1); the pressure difference between the inside of the home and the soil; the infiltration rate of the home; the moisture content of the soil; and the number and size of entry points into the home.
A 1994 study by the EPA showed inconsistent results between radon and air tightness (EPA 1994). Research conducted by Oak Ridge National Laboratory (ORNL) on this topic (Pigg et al. 2014) showed that statistically significant net increases in radon levels occurred in weatherized homes, even though the increase was modest. For example, the average radon levels pre-weatherization in EPA zone 1 (high) was 2.4 pCI/l (285 study sites) in the treatment group and 2.7 pCi/l in the control group (162 study sites). After weatherization the treatment group went up by 0.29 pCi/l and the control group went down by 0.5 pCi/L. Note that the changes in radon levels were related to outdoor temperature. This study is currently being repeated controlling for geographical location and season, and using different radon measurement methods. The best recommendation is to test after weatherization has been completed and if the levels are too high, then it can be mitigated with pressure management and venting.
Radon abatement is unfortunately not currently allowable under the Weatherization Assistance Program. The Colorado Department of Public Health and Environment has a low income radon mitigation assistance program that was just signed into law in April 2016.
Health effects studies of weatherization, which have mostly been done recently on multifamily residential buildings, have shown varying outcomes. Wilson et al. (2013) showed that self-reported respiratory symptoms were more frequent after retrofit (-26%), residents had greater sleep disruption due to asthma (-28%), and improvements in general health were reported (reduced asthma medication usage, hypertension, sinusitis). There was no provision of mechanical ventilation in the retrofits. Breysse et al. (2011) reported on a green renovation of three multifamily affordable housing buildings that resulted in adults reporting significant improvement in overall, asthma, and non-asthma respiratory health, and significant improvement in non-asthma respiratory health. Renovations included adding continuous and spot ventilation. Energy reductions of 45% were realized. A drawback to this study was that pre-retrofit health was reported retrospectively one month after moving into renovated apartments. None of these studies measured radon.
Breysse, J, et al. (2011). Health Outcomes and Green Renovation of Affordable Housing. Public Health Reports 126(Suppl 1):64–75.
EPA (1994). Assessment of the effects of weatherization on residential radon levels. https://cfpub.epa.gov/si/si_public_record_Report.cfm?dirEntryID=126455, accessed Aug 2016.
Noris, F, et al. (2013). Indoor environmental quality benefits of apartment energy retrofits. Build Environ 68:170–178. doi:10.1016/j.buildenv.2013.07.003
Pigg, S., Cautley, D., Francisco, P. W., Hawkins, B., & Brennan, T. (2014). Weatherization and Indoor Air Quality: Measured Impacts In Single-Family Homes Under The Weatherization Assistance Program. (No. ORNL/TM-2014/170). weatherization.ornl.gov. Oak Ridge, TN.
Wilson, J, et al. (2013). Watts-to-Wellbeing: does residential energy conservation improve health? Energy Efficiency, 1–10. doi:10.1007/s12053-013-9216-8.