BARRIER: Building Assessment of Radon/Moisture Reduction with Energy Retrofits

Project Funder: University of Illinois – Urbana/Champaign (UIUC) (subgrant from the U.S. Department of Housing and Urban Development)

Project Partners:
 UIUC, Tohn Environmental StrategiesCamroden Associates, the Community Action Program Belknap-Merrimack Counties, Inc.Southern New Hampshire Services, and multiple agencies in Illinois that will be coordinated with the Illinois Department of Commerce and Economic Opportunity (DCEO)

Project Contact:
 Jonathan Wilson,, 443.539.4162

What we studied:
 The effect of precautionary measures when coupled with energy efficiency on radon levels in housing. A 2014 study found that radon levels increased significantly after homes were weatherized but precautionary measures were not used.

What we found:
 There was no statistically significant change in radon levels in homes where the precautionary measures were applied along with energy efficiency work.

Why it matters:
 Currently, the U.S. Weatherization Assistance Program requires energy efficiency providers to use a set of precautionary measures in communities where the risk of radon is high. This study offers support that this policy should continue to be enforced. Additional research is ongoing to determine whether energy efficiency programs that are not funded by the U.S. Department of Energy should adopt this practice.

Project Description: 
The Building Assessment of Radon/Moisture Reduction with Energy Retrofits (BARRIER) study examined the question whether specific low-cost, simple weatherization activities reduce radon exposures and offer any moisture reduction benefit. The work was conducted by five local weatherization agencies in Illinois and New Hampshire. They represented two different climate zones in areas with high radon levels. The study enrolled 98 units in two study arms to determine the effectiveness of the low-cost measures. The first arm included 56 homes undergoing weatherization with the low-cost enhanced sealing in basements and crawl spaces. The second arm had 42 homes that received energy retrofits without the enhanced sealing. Radon, moisture, and temperature were measured in these homes for two weeks before and after weatherization (Figure 1). About one third of the homes had extra tests at one year post-work. Additionally, homes in the same vicinity as the study homes were selected as control homes and monitored using continuous radon monitors.

Baseline basement conditions were similar in both arms of the study: Only about one third of homes had uncovered sump pump wells, and one quarter had uncovered dirt before work. As a result, the difference between enhanced and standard treatments were not large enough to observe an effect. We modified our analysis to focus on the change in radon levels from before to after weatherization for all 98 homes in the study. These changes were compared to prior studies of weatherization and radon.In our study, we found control-adjusted radon levels on the lowest living level of homes increased an average of 7.5% from pre-treatment levels. The difference between pre- and post-weatherization levels was not statistically significant. A previous study of weatherization found that the average control-adjusted lowest living level increase was 22%. Our findings suggest that recently implemented weatherization practices help to dampen the impact of traditional energy retrofit measures on radon. In particular, the addition of continuous ventilation from bathroom exhaust fans seems to help keep radon close to its pre-weatherization levels.

NCHH is currently preparing an article to fully describe these results with publication anticipated in late 2018.

Policy makers advised the researchers that a larger sample size was needed to help them formulate better radon control guidance for energy efficiency providers. The research team is now completing the BARRIER-X (Expansion) study.


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