Preventing Radon Exposure Radon Control In New Homes: A Meta-Analysis of 25 Years of Research

Transcription

1 Preventing Radon Exposure Radon Control In New Homes: A Meta-Analysis of 25 Years of Research William J. Angell Professor and Director Midwest Universities Radon Consortium University of Minnesota 2013 University of Minnesota 1

2 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 This does not say that testing and mitigation are unimportant; rather we need to do more on the new construction front 2013 University of Minnesota 2

3 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 Increasingly becoming the focus in the U.S University of Minnesota 3

4 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 U.S. EPA (1999) Design of a program to measure the effectiveness of passive radon-resistant new construction 2013 University of Minnesota 4

5 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) Arvela, et al. (2008) Radon prevention and mitigation in Finland: Guidance and practices in AARST Symposium Proceedings 2013 University of Minnesota 5

6 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 Whether quality assurance and/or quality control were reported 2013 University of Minnesota 6

7 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 Arvela, Holmgren and Reisbacka (2011) present the results from the first national survey of radon-control systems in 1561 new Finnish houses 2013 University of Minnesota 7

8 Radon Concentration by Foundation Type: Finland (Arvela, Holmgren and Reisbacka [2011]) Rn Concentration (Bq m -3 ) Foundation Type # Houses Average Median Slab-on-grade Monolithic Slab Crawlspace Semi-basement and Basement No Information Total These data are from a 2009 national random survey of Finnish houses built between 2004 and 2006 when new building code requirements were enacted The new code required a loop of subslab radon pipe, sealing of the cold joint using a strip of sealed bitumen felt, and a radon vent pipe discharge above the roof 2013 University of Minnesota 8

9 Effects of Passive Methods in Finnish Slabon-Grade Houses(Arvela, Holmgren and Reisbacka [2011]) Passive Preventive Measure None PSD Piping & Sealing PSD Piping & No Sealing Number of Houses Average Rn Concentration (Bq m -3 ) Median Rn Concentration (Bq m -3 ) House Rn Compared to Local Rn Concentrations 0% 57% 41% These data are from a 2009 national random survey of Finnish houses built between 2004 and 2006 when new building code requirements were enacted 2013 University of Minnesota 9

10 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 Should be interpreted with caution since many of the houses had deficiencies in radon-control techniques 2013 University of Minnesota 10

11 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)... a 55% average reduction in indoor radon concentrations University of Minnesota 11

12 PSD Cap-on/Cap-off Studies (Bq m -3 ) Study (alpha order) Number Houses Capon Cap -off % Notes Brehm, PSD compromised; 2 day Rn tests, location & season unspecified Dewey, 1994 Basement Basement Rn tests; 36 tested same season First Floor First floor Rn tests; 36 tested same season Average Fort Collins, Houses built 2005; Rn tests length & location unspecified Hagerty, PSD compromised; 5-7 day Rn tests, season & location unspecified Hanson, PSD compromised; January basement Rn tests; test length unspecified LaFollette, day Rn tests on the lowest level suitable for occupancy Najafi, of 14 houses with PSD tested NAHB, 1996 Winter PSD compromised; winter lowest level Rn tests; test length unspecified Summer Summer Rn tests in lowest level; test length unspecified Average Saum, Cap-off approximate value; winter Rn tests Snead, PSD compromised; average 7 day winter Rn tests; location unspecified Tyson, Main floor 48 hour Rn tests; testing season unspecified Weiffenbach, Basement, 6+ day, winter Rn tests Total 224 Overall Weighted Average % Reduction 2013 University of Minnesota 12

13 PSD versus ASD Radon Control in New Houses The following table summarizes the research findings of 9 studies on the comparative performance of PSD and ASD system in 61 houses Overall, ASD offers More than an 80% reduction in indoor radon concentrations in new houses Greater radon reduction than PSD 2013 University of Minnesota 13

14 PSD vs. ASD Performance Study # of Houses Radon Tests (Bq m -3 ) PSD PSD Capped Open ASD Notes Brennan, Five day Rn tests, season & location unspecified Clarkin, April-May, 6 day basement Rn tests Dewey, Basement Rn tests Keränen, Two month, first floor Rn test, seasons varied Lewis, Location, season & length of Rn tests generally unspecified Najafi, Four first floor Rn tests, seasons & length of tests unspecified Saum, Location, season & length of Rn tests unspecified Tyson, Main floor 48 hour Rn tests; testing season unspecified Weiffenbach, PSD Rn with poor sealing; ASD with sealing Total 61 Weighted Averages PSD Capped to ASD % reduction PSD Open to ASD % reduction 2013 University of Minnesota 14

15 New Construction Radon Control Standard RRNC (Reducing Radon in New Construction) 2.0 American National Standard Institute (ANSI)/ American Association of Radon Scientists and Technologists (AARST) CCAH 2013 Written in building code language Rough-in or activation of a soil depressurization system Radon test required before installing a fan Long-term radon test after occupancy 2013 University of Minnesota 15