Preventing Radon Exposure
Radon Control In New
Homes: A Meta-Analysis of
25 Years of Research
William J. Angell
Professor and Director
Overview
Importance of Radon Control in New
Houses
•
As documented in a 2008 paper I authored,
the U.S. has more
housing units with elevated radon than anytime in our history
– The major reason for this problem was that in a typical year more new
homes were built that had elevated than the number of existing
homes that mitigated
–
This situation is also true for the vast majority of the world
• It has been demonstrated that, in many cases, a public sector
emphasis on radon control in new housing was more cost-effective
for population-based risk reduction than a testing/mitigate
approach
Overview
Basic Radon Control Strategies
• Passive sealing only
–
For example, subslab membrane
–
Focus in the UK and Ireland
• Passive soil depressurization
–
Permeable subslab layer, soil gas vent riser through conditioned portion
of the house and terminating above the highest roof, thorough sealing
of soil contacted foundation elements
–
Historically, the focus in the U.S.
• Active soil depressurization
–
Permeable subslab layer, soil gas vent riser with an in-line fan through
conditioned portion of the house and terminating above the highest
roof, thorough sealing of soil contacted foundation elements
Overview
A Sample of U.S. Guidance Documents,
Standards, and Code
(1:2)
• U.S. EPA (1987)
Radon Reduction in New Construction, An Interim
Guide
• ASTM (1990)
Emergency Standard Guide for Radon Control Options
for the Design and Construction of New Low Rise Residential
Buildings
• Clarkin and Brennan (1991)
Radon-resistant Construction Techniques
for New Residential Construction (EPA)
• U.S. EPA (1994)
Model Standards and Techniques for Radon Control
in New Residential Buildings
• Council of American Building Officials (1995)
One and Two Family
Dwelling Code
Overview
A Sample of International Guidance
Documents, Standards, and Code
• Clavensjö and Åkerblom
(1994)
The Radon Book: Measures
against Radon
• Building Research
Establishment
(BRE) (1999a,
1999b) Construction of New
Buildings on Gas-contaminated
Land and Radon: Guidance on
Protective Measures for New
Dwellings
• Roserens, et al.
(2000) Swiss
Radon Handbook
• National Building Code of Finland
(Ministry of the Environment, 2003)
Results
Overview of Results
•
The total number of documents reviewed was 57
•
As reflected the following slide,
–
36 papers of the more data rich publications are summarized by
•
Author(s) and year of publication
•
Number of houses and number of communities in the study
•
Whether the houses were built according to EPA guidance or similar
codes
•
Radon testing details
•
Whether pressure differential measurements were reported
•
Types of radon control techniques used or assessed in the study
Results
Some Pivotal Papers
•
Pivotal documents included:
– Murane (1988)
describing data from 148 new houses in
EPA’s New House Evaluation program built by 5 builders in
CO and MI
– EPA (1999)
guidance document or protocol on measuring
the effectiveness of PSD systems
– Weiffenbach and Marshall (2003)
reported very extensive
data logging in 8 houses
Results
Radon Concentration by Foundation Type:
Finland
(Arvela, Holmgren and Reisbacka [2011])
Rn Concentration (Bq m
-3)
Foundation Type
# Houses
Average
Median
Slab-on-grade
798
97
68
Monolithic Slab
18
36
27
Crawlspace
231
43
29
Semi-basement and Basement
193
161
97
No Information
321
89
54
Total
1561
95
58
•
These data are from a 2009 national random survey of Finnish
houses built between 2004 and 2006 when new building code
requirements were enacted
Results
Effects of Passive Methods in Finnish
Slab-on-Grade Houses
(Arvela, Holmgren and Reisbacka [2011])
•
These data are from a 2009 national random survey of Finnish houses
built between 2004 and 2006 when new building code requirements
were enacted
Passive Preventive Measure
None
PSD
Piping &
Sealing
PSD
Piping &
No
Sealing
Number of Houses
230
166
111
Average Rn Concentration (Bq m
-3)
90
82
98
Median Rn Concentration (Bq m
-3)
68
53
59
Results
Winter and Summer Rn Concentration
with Cap-on/Cap-off NAHB Houses
Winter
Summer
Stack Closed
192 (5.2 pCi/L)
133 (3.6 pCi/L)
Stack Open
93 (2.5 pCi/L)
67 (1.8 pCi/L)
Percent Reduction
52%
50%
•
The data in this table
– Reflects seasonal variation - stack effect in 22 houses with PSD
systems in 6 states
• But the similarity in percentage of radon reduction is notable
Results
PSD Cap-on/Cap-off Studies
•
The following table summarizes the findings of
12 studies of
radon concentrations in 224 houses with PSD systems
:
–
Capped (nonfunctional)
•
The average radon concentration was 231 Bq m
-3(6.2 pCi/L)
–
Open (functional)
•
The average radon concentration was 127 Bq m
-3(3.4 pCi/L)
Results
PSD Cap-on/Cap-off Studies
(Bq m
-3
)
Study (alpha order)
Number Houses
Cap-on
Cap
-off %
NotesBrehm, 2002 20
105 93 -11
PSD compromised; 2 day Rn tests, location & season unspecified Dewey, 1994 Basement 44196 81
-59
Basement Rn tests; 36 tested same seasonFirst Floor 44
81 44
-46
First floor Rn tests; 36 tested same seasonAverage
139 63 -55
Fort Collins, 2006 65
296 148 -50
Houses built 2005; Rn tests length & location unspecifiedHagerty, 2003 13
344 278 -19
PSD compromised; 5-7 day Rn tests, season & location unspecified Hanson, 2005 8244 125 -49
PSD compromised; January basement Rn tests; test length unspecified LaFollette, 2001 22337 163 -48
7 day Rn tests on the lowest level suitable for occupancyNajafi, 1995 2
252 257 +2
2 of 14 houses with PSD testedNAHB, 1996 Winter 22
192 93 -48
PSD compromised; winter lowest level Rn tests; test length unspecified Summer 22133 67 -50
Summer Rn tests in lowest level; test length unspecifiedAverage
163 80 -49
Saum, 1990 1
1110 278 -75
Cap-off approximate value; winter Rn testsSnead, 2003 5
269 192 -25
PSD compromised; average 7 day winter Rn tests; location unspecified Tyson, 1995 1588 94 +7
Main floor 48 hour Rn tests; testing season unspecifiedWeiffenbach, 2003 7