Radon: What We Have Learned From Retrofit Studies Stacy Gloss, research specialist Indoor Climate Research and Training University of Illinois 1 In accordance with the Department of Labor and Industrys statute 326.0981, Subd. 11, This educational offering is recognized by the Minnesota Department of Labor and Industry as satisfying 1.5 hours of credit toward Building Officials and Residential Contractors continuing education requirements. For additional continuing education approvals, please see your credit tracking card.
2 Learning Objectives Identify radon zones on EPAs radon zone map. Describe differences on radon levels from two residential ventilation strategies. Recognize some patterns of correlation between temperature and radon. List pros and cons of different radon test methods. Discuss patterns of variability of radon from multiple factors. Describe impacts of different retrofit measures. 3 Topics
What is radon? How is it identified? (test methods) Whats does EPA tell us to do when practitioners find radon in a home? What are findings from studying radon in residential retrofit settings? Conclusions and Discussion 4 Disclaimer: I am not a Ph.D. scientist. Im not a policy wonk. Im not an epidemiologist.
Involved in research Fits easily in crawl spaces 5 Survey Question #1 Do you consider yourself to have moderate to advanced level of radon knowledge? (Raise your hand. Dont be shy.) 6 Survey Question #2
Have you ever tested a home for radon? 7 Survey Question #3 Are you familiar with active soil depressurization and other radon mitigation techniques? 8 What is radon? 9
What is radon? Naturally occurring radioactive gas that can cause lung cancer. You cant see or smell or taste radon. Radon can have a big impact on
indoor air quality. (EPA) 10 Radon Science Chemical element with symbol Rn. Occurs naturally as a decay product of radium. Half-life of 3.8 days. Alpha particles from Ionizing Radiation are dangerous to human health. 11 Uranium decay chain
12 What are we concerned about? Radon decay products alpha particles. Alpha particles are solids and can stick to surfaces such as dust particles in the air that are breathed in. Radon can get into the lung through respiration, and can decay to radioactive solids or radon progeny.
Can damage lung cells and cause lung cancer 13 Radon measurement units Most common unit in U.S. pCi/l = picocuries per liter For each pCi/l there are 2.2 radioactive disintegrations per minute (source: radon-faq.com) EPA Threshold 4.0 pCi/L 14 Where is radon?
15 EPA Radon Map 16 17 EPA Radon Policy Developed in early 1980s Recommend mitigation for levels > 4 pCi/l 18 The Story of Stanley Watrous
The Watrous house tested at 2,700 picocuries per liter, 700x the recommended level. 19 How to measure radon and variability in results 20 Measurement of Radon Many methods SHORT TERM - 2 4 day tests For example, short term electrets with short term sampler
Sampler Ele ctr et 21 Measurement of Radon Charcoal canisters - ~ 2 7 days, averaging Most common type of test kit 22
Measurement of Radon LONG TERM - AlphaTracks (~91 days or greater, averaging) LONG TERM ion chambers, more than 3 weeks, any period, averaging 23 Measurement of Radon
ANY DURATION Continuous Radon Monitors 10 Days max Hourly Data Modified for research Hourly Data, Unlimited Days 24 Measurement of Radon What EPA says (EPA 1993): Do a short-term test Radon < 4 pCi/l
4 pCi/l < Radon < 10 pCi/l Radon > 10 pCi/l Do a second test Preferably at least 90 days Can also do a second short-term You are done ST: a v LT: > erage > 4? 4?
< 4? e g vera a : ST 4? LT: < 25 Mitigate Measurement of Radon What is usually done (esp. for real estate transactions):
Do a short-term test Radon < 4 pCi/l 4 pCi/l < Radon < 10 pCi/l You are done Radon > 10 pCi/l Mitigate (or agree on an allowance with the buyers) 26 Measurement of Radon
Remember, action level is intended to be an ANNUAL AVERAGE Lots of work on variability by Steck et al. Variability around an annual average for multiple periods Annual variability (year-to-year) 27 Steck et al. variability around annual average (Steck 2005) 28
Steck et al. variability around annual average (Steck 2005) 29 2 Radon level, Site 3 living level, pCi/l 3 4 5 6 7 Building America Site 3 Living Level
Time Hourly 1-week 30 4-day 2-week Weather 4 R a d o n le v e l, S ite 1 liv in g le v e l, p C i/l 6 8 10 12
Radon higher when temperatures are warmer Radon Site 1 Living Level -20 0 20 40 Outdoor Temperature, F Outdoor Temperature, F 31
60 80 2 2 R a d o n le v e l , S i te 3 l i v i n g l e v e l, p C i/l 3 4 5 6 7 0
-20 0 0 20 40 Outdoor Temperature, F 20 40 Outdoor Temperature, F 60 60 2
R a d o n l e v e l , S ite 1 li v i n g le v e l , p C i/ l 6 8 10 12 Site 1 -20 0 80 Site 3 80 -20
-20 R a d o n l e v e l , S ite 2 li v in g le v e l , p C i /l 4 6 8 10 0 Temperature R a d o n l e v e l , S i te 5 f o u n d a ti o n le v e l , p C i/l 5 10 15
20 25 R a d o n le v e l , S i te 4 f o u n d a ti o n l e v e l , p C i/l 5 10 15 4 -20 20 40 Outdoor Temperature, F 60 20
40 Outdoor Temperature, F 60 0 0 20 40 Outdoor Temperature, F Site 4 20 40 Outdoor Temperature, F
32 R a d o n l e v e l , S i te 5 l i v i n g l e v e l, p C i/l 5 10 15 -20 Radon Living Level R a d o n le v e l , S i te 4 l i v i n g l e v e l, p C i/l 4 6 8 10
R a d o n l e v e l , S ite 3 fo u n d a ti o n l e v e l, p C i /l 4 6 8 10 12 R a d o n l e v e l, S i te 2 fo u n d a ti o n le v e l , p C 5 10 15 20 R a d o n l e v e l , S ite 1 fo u n d a tio n le v e l, p C 5 10
15 20 Foundation 80 -20 80 -20 60 60 80 0 20
40 Outdoor Temperature, F 0 20 40 Outdoor Temperature, F 80 -20 -20 0 0
60 80 Site 2 60 80 20 40 Outdoor Temperature, F Site 5 20 40 Outdoor Temperature, F
60 80 60 80 Colder temperatures what is going on? Dont know for sure Hypotheses: Yes, there is greater stack effect pulling on the ground, but there is also greater dilution and more of that comes from
outside than the ground HVAC operation may (1) mix and get radon upstairs; and (2) increase air exchange rate (i.e., get it up and out) Bill Rose lower soil temps = higher soil moisture content and radon is soluble in water? (Untested) 33 How good are various test methods? Probably all pretty good at measuring what happened when they were there. Instrumentation itself is not problematic. The problem is that radon is so variable levels you
see this 2 or 4 days may not be the levels you will see 2 or 4 weeks from now. 34 Our Research Studies 35 HEALTH-V Study 36 Goals and Methods
Compare benefits of differing ventilation standards ASHRAE 62-1989 vs. ASHRAE 62.2 Observe changes in IAQ from energy retrofits Formaldehyde, Total VOCs, Radon, CO2, CO, Humidity Conduct preliminary and final health surveys 37 37 Sites Tested Tested 52 homes Chicago area, 35 homes in Indiana
Randomly selected Control homes weatherized to ASHRAE 62-1989 (passive infiltration) Treatment homes weatherized to ASHRAE 62.2-2010 (mechanical ventilation) 38 Exhaust ventilation Radon, basement Radon Pre-Wx all Post-Wx all Pre-Wx 62-1989 Post-Wx 62-1989 Pre-Wx 62.2-2010 Post-Wx 62.2-2010
Number (n) 51 23 28 Mean (pCi/l) Geo-mean (pCi/l) 5.1 2.6
6.0 3.0 6.3 3.0 6.7 2.9 4.2 2.4 5.4
3.1 Green indicates statistical significance at p < 0.10 39 T-test p-value 0.330 0.888 0.073 Exhaust ventilation Radon, 1st floor Radon Pre-Wx all Post-Wx all Pre-Wx 62-1989
Post-Wx 62-1989 Pre-Wx 62.2-2010 Post-Wx 62.2-2010 Number (n) 46 21 25 Mean (pCi/l) Geo-mean (pCi/l) 2.7
1.8 2.6 1.4 2.4 1.7 2.8 1.6 3.0
1.9 2.4 1.3 Green indicates statistical significance at p < 0.10 40 T-test p-value 0.143 0.824 0.067 Building America Study
Conducted by researchers at ICRT, homes in Champaign, IL Intended to evaluate potential for air sealing between foundation and first floor to reduce radon migration Principle of do no harm as opposed to solving high radon problems 41 Objectives
1. Investigate effectiveness of targeted floor air sealing at isolating the living space from the foundation space 2. Monitor effect of air-sealing on radon levels in foundation and living spaces 3. If specific air-sealing targets can be prescribed to address radon levels 4.
Discover the role that ductwork plays in the transport of radon to the living space 42 Sample House Characteristics 3 Groups: Fall 2013, Spring 2014, Summer 2014 11 Crawlspace, 4 Basement + Crawlspace(s) Average home age: 1966; Newest: 2005; Oldest:
1890 Average CFM50: 3239: Tightest: 1542; Leakiest: 5896 43 Study Design 15 homes monitored in 3 groups of five monitored for ~90 days Monitor for a month Retrofit 2-3 of them, monitor for a
month Retrofit the others, monitor for a month Monitoring was continuous in living level, crawlspaces and basements 44 Retrofit Measures Applying mastic and foil tape to duct work Expanding urethane foam at penetrations beneath the floor
Repairing or replacing degraded missing duct work 45 Wide open ducts in crawl space BEFORE AFTER 46 20 15
Living Level Radon Windows Open / Closed PR-12 radon and windows closed open 10 5 0 Foundation Radon
0 10 20 47 30 Basements and First Floors track each other? Site 3 Radon level, Site 3 living level, pCi/l 3 4 5
6 Radon level, Site 5 living level, pCi/l 5 10 15 7 Site 5 r2 = 0.1801 2 r2 = 0.5877
Radon level, Site 3 foundation level, pCi/l Radon level, Site 5 foundation level, pCi/l Worst agreement Greatest agreement 48 Results Treatment lead to measureable change in zone pressure measurements with greater isolation of foundation and living space. Improved isolation did not lead to statistically significant change in living level average radon
Reduced; Even; Increased No changes could be conclusively attributed to the treatments. 49 Case Studies Air handler fan ran continuously living level and crawl radon were within 10% Very large return duct leaks after sealing radon noticeably dropped
50 National Weatherization Evaluation Report released 2015 Weatherization and Indoor Air Quality: Measured Impacts in Single-Family Homes Under the Weatherization Assistance Program Scott Pigg, Energy Center of Wisconsin Dan Cautley, Energy Center of Wisconsin Paul Francisco, University of Illinois Beth Hawkins, Oak Ridge National Laboratory Terry Brennan, Camroden Associates 51 Sites Tested 514 single-family homes
35 states 88 weatherization agencies participated 2010/2011 heating season Over sampled in high radon areas Tested radon using activated charcoal canisters 7 day test before and after Wx 52 Key Take Aways Average single-family home had heating-season indoor radon levels of 1.9 0.1 pCi/L Tighter homes tend to have higher radon levels Data suggest Wx results in small, statistically significant increase in radon levels.
Average increase of 0.4 0.2 pCi/L Most states Wx programs used ASHRAE 62-1989 (Building Tightness Limit) 53 National Weatherization Assistance Program Impact Evaluation: Impact of Exhaust-Only Ventilation on Radon and Indoor Humidity A Field Investigation Researcher Scott Pigg, Energy Center of Wisconsin Evaluated 62.2 compliant exhaust ventilation 18 homes in Colorado, Iowa, Minnesota and Ohio Toggled on/off ventilation and results suggest that 62.2 compliant exhaust ventilation can reduce radon levels.
54 55 results Radon levels declined or remained about the same for all homes in the study when the ventilation was operated. On average, the installed ventilation reduced radon levels by 12 7 percent. This suggests that in most cases, the dilution effect of exhaust-only ventilation outweighs any tendency to increase the radon entry rate by depressurizing foundation spaces.
FIND THE REPORTS AT bit.ly/ORNLWxEval 56 Building Assessment of Radon/Moisture Reduction w/ Energy Retrofits (The BARRIER Study) University of Illinois at Urbana-Champaign National Center for Healthy Housing Tohn Environmental Strategies 02/29/2020 57
57 Need for the Study Questions: Can low-cost, passive measures that are aligned with normal weatherization measures keep radon levels from increasing as a result of WAP activities? Are there also moisture benefits? 02/29/2020 58 58
Enhanced Measures Crawl spaces Plastic groundcovers carefully installed such that all seams are sealed and the plastic is sealed to the perimeter walls and any foundation supports Air sealing of ducts located in the crawl space Air sealing of the floor between the living space and the crawl space Air sealing around any interior crawl space accesses 59 59
Enhanced Measures Basements Plastic groundcovers over any exposed earth, carefully installed such that seams are the plastic is sealed to concrete Installation of sealed sump pump covers Caulking of cracks in below grade concrete Air sealing of the floor between the basement and first floor, if the basement is not the lowest living level Air sealing of return ducts located in the basement 60 60
Conclusions What were still learning Impact of retrofits Impact of ventilation, esp. exhaust How weather impacts radon Results suggest opposite trend from known trend Variability between houses from same weather exposure Variability from basements to first floors within homes (We are currently working on these issues) 61 Questions?
For more information contact [email protected] 62 Radon vs. stack effect/air sealing Where do we air seal? Most is at ceiling, some also at floor 63 Radon vs. stack effect/air sealing
What happens when we air seal at the floor? Reduces radon entry potential by reducing pathways 64 Radon vs. stack effect/air sealing What happens when we air seal at the ceiling? Neutral level goes lower Reduces negative pressure on the ground 65 Radon vs. air sealing
So, when we air seal at the ceiling, we do indeed make it harder for radon to get out, but we also make it harder for radon to get in When we air seal at the floor we also make it harder for radon to get in On balance? Difficult to say, but at the very least it is clear that the assumption that radon entry is unchanged is an assumption that should be rejected 66
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