In response to this morning’s radio segment from the Iowa Environmental Focus, we received an email informing us that the issues with radon concentrations in energy efficient homes are more complicated than we initially realized. Dr. William Field of the University of Iowa shared with us a report he prepared for the EPA last year, which helps clarify this topic.
In his report, Field indicates that the effects energy efficient homes have on radon concentrations are often overstated, and there are ways to implement energy efficient measures without seriously impacting in-home radon concentrations:
There is widespread, perhaps erroneous in many cases, belief that increase weatherization and energy efficiency of homes significantly contributes to increased residential radon concentrations. For example, the latest ATSDR (2010) statement on radon includes the following statement, “In indoor locations, such as homes, schools, or office buildings, levels of radon and radon progeny are generally higher than outdoor levels and may be particularly high in some buildings, especially in newer construction that is more energy-efficient.” However, in their book, “Radon’s Deadly Daughters”, Edelstein and Makofske (1998) label the belief that radon concentrations in energy efficient homes are differentially elevated as compared to other homes, “the myth of the tight house”. They noted that high insulation rates as well as energy efficient homes, relying on several studies published primarily during the 1980s to support their view, have limited influence on increased radon concentrations. However, the authors concede that tightening homes may increase radon concentrations for homes that have significant sources of indoor radon sources (e.g., waterborne radon, building materials).
Since 1990, numerous studies noted that past and current energy efficiency measures do not necessarily increase radon concentrations (EPA 1994, Chi and Laquatra 1990, Mullen and Nevissi 1990). Nonetheless, continued uncertainty remains about the impact of weatherization and energy efficiency on residential radon concentrations. In late fall of 2009, Senator Mark Udall wrote to the Secretary of Energy, Steven Chu, and EPA Administrator, Lisa Jackson, expressing his concern about the Department of Energy’s ongoing weatherization program in regard to indoor pollutants, including radon (attached). In a March 2010 letter of response to Senator Udall, Steven Chu and Lisa Jackson indicated that both the DOE and EPA will assure that weatherization practices will do no harm and will evaluate the effect of weatherization on indoor radon (attached). If energy efficiency and weatherization guidelines include consideration of air exchange rates and ventilation, climate change driven housing guidelines for energy efficiency should have less of an effect on residential radon concentrations. However, if outdoor make-up air, with increased air pollutants, is used to reduce residential radon concentrations, indoor air quality may suffer unless the air is filtered prior to use.