Post on 22-Feb-2022
NRC and Radon Control Technologies
Prepared by: Dr. Liang Grace Zhou, Gnanamurugan Ganapathy, Gang Nong,
Ethan Li, and Jeff Whyte
National Research Council Canada - Construction Research Centre
For: the 14th International Workshop on the Geological Aspects of Radon Risk
Mapping
February 7, 2019
HC-RPB cross-Canada survey of 14,000 homes: ~7% of Canadians living in
homes with a radon level >200 Bq/m3
Background
16% lung cancer deaths attributable to radon exposure 3,200/yr in Canada
NRC’s Radon Research
• Why
Mission-driven channel for federal investment in R&D
Technical inputs for regulators, standards committees, and radon
practitioners
Emerging “radon industry”
Public awareness and verified solutions
• Funding sources
Federal Funding-Taking Action on Air Pollution
Interdepartmental agreement with Health Canada Radiation Protection
Bureau
Fee for Service contracts with industrial clients
• How
NRC’s multidisciplinary expertise, unique facilities, and links to industry
Canadian Construction Material Centre and National Building Code
3
2015 NBC Part 9
• Sealed soil gas barrier (e.g. 6 mil polyethylene based on
CAN/CGSB-51.34-M86)
• 100 mm Gas permeable layer (e.g. gravel) beneath air barrier
• Sump pit cover required to be airtight
• Consistent requirements for ground cover
• Sealed, capped, and labeled rough-in pipe
with inlet near centre of slab
and top end ready for Active Soil Depressurization
Radon in the National Building Code of Canada:
Housing and Small Buildings
2015 NBC Part 5 – Environmental Separation
• Control of Air Leakage
Minimize the ingress of airborne radon from the ground with an aim to
controlling the indoor radon concentration to an acceptable level
2015 NBC Part 6 – HVAC
• Good HVAC Engineering Practice
EPA/625/R-92/016, “Radon Prevention in the Design and Construction
of Schools and Other Large Buildings” Ventilation and ASD
Appendix Guidance
• Health Canada Guide for Radon Measurements in Public Buildings
Radon in the National Building Code of Canada: Large
Buildings & Optional for Small non-Residential Buildings
6
Radon Control Research Activities
• Prevent soil gas entry
Sub-slab gas permeable layer and air barrier systems
• Active sub-slab depressurization (ASD)
Leakage through radon control fans
Energy penalty and impact on soil temperature
Insulation of stacks in unheated attic space
Backdrafting from combustion appliances
• Indoor radon dilution
Air tightness, air change rate, HRV, and radon concentration
• A combination of strategies
Prevent Soil Gas Entry:
Radon Infiltration Building Envelope Test System (RIBETS)
Radon infiltration through floor assembly with
• Membrane
• Special property concrete
• Sub-slab ventilation panel
• Sub-slab spray foam
• HVAC components (HRV/ERV) and demand control
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Prevent Soil Gas Entry:
Radon Diffusion Test Chamber
8
Material evaluation ISO/TS 11665-13: 2017
Test Procedure
• Air leakage test
• Phase of non stationary diffusion
• Phase of stationary diffusion
• Data post-processing and analysis
Radon Diffusion
9
One-dimensional transient governing equation for radon diffusion
Where D, is the diffusion coefficient (m2/s), calculated based on the dosing [Rn]
level, the slope of the increase of [Rn] in the receiving compartment, the
dimensions of the sample, and the dimensions of the receiving compartment.
D∂2𝐶 𝑥,𝑡
∂𝑥2− λ𝐶 𝑥,𝑡 =
𝜕𝐶 𝑥,𝑡
𝜕𝑡
10
Is Radon Diffusion Coefficient a Suitable Performance
Indicator or NOT?
• Generally, materials with higher D are considered more permeable to
radon.
• However, D is a material property that depends mainly on its chemical
composition and is not affected by its thickness.
• The thickness of building materials for sub-slab air barrier systems
usually ranges between 10-4 m and 10-1 m.
MaterialThickness
(m)D (m2/s)
Receiving
Radon
(Bq/m3)
1 1.52*10-4 8.05*10-12 198300
2 1.00*10-3 8.58*10-12 108385
3 2.70*10-3 1.12*10-11 10500
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A New Approach to Assess Radon Barriers
Radon Resistance RRn (s/m) (Jiranek and Svoboda, 2017)
Where d is the thickness of the material (m), λ is the decay constant (1/s)
l is the radon diffusion length in the material (m)
𝑅𝑅𝑛 =sin ℎ 𝑑 𝑙
𝜆𝑙
Material 1 2 3 4 5 6 7 8 9
Thickness (m) 2.54*10-2 1.52*10-4 1.00*10-3 1.00*10-3 2.54*10-2 1.50*10-3 2.70*10-3 2.70*10-3 5.08*10-4
D (m2/s) 2.25*10-7 8.05*10-12 2.10*10-11 2.03*10-11 2.89*10-10 8.58*10-12 1.04*10-11 1.12*10-11 --
RRn (s/m) 1.13*105 1.90*107 4.85*107 5.01*107 1.74*108 1.91*108 2.60*108 2.99*108 --
Receiving Radon (Bq/m3)
847872 198300 144311 109178 51362 49664 19448 10500 0
12 materials have been tested (special property concrete, membranes,
spray foam, foam board, tape and sealant)
CCMC Technical Guide for “Medium Density (MD) Spray Polyurethane
Foam Insulation (SPUF) for Soil Gas (Radon) Control beneath Concrete
Slabs-on-Ground” 2017
12
ASD: Radon Fan Enclosure Leakage Test Rig
Why: Radon control fans are located in the basements of Canadian homes
How: NRC’s air permeability test apparatus and tracer gas leakage test rig
What: Test 5 models/8 fans from 4 manufacturers
Outcomes: Radon fan criteria- Canadian General Standard Board
CAN/CGSB-149.12-2017 Radon Mitigation Options for Existing Low-Rise
Residential Buildings
Canada US
(Illustration courtesy of Health Canada)
ASD: Impact on Heating Energy Use and Soil Temperature
Performance of Passive Radon Stack
ASD with Ground
Exhaust (2012)
ASD with Roof Line
Exhaust (2012)
Expected Test House Daily Energy
Consumption (MJ)309.9 360.4
Increased Daily Consumption (MJ) 20.2 15.3
Increase, % 6.5% 4.2%
Canadian Centre for Housing Technology
ASD: Stack Insulation, Backdrafting from Combustion
Appliances, Gable-ended Discharge
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• Insignificant risk of backdrafting from combustion appliances
due to building depressurization
• Gable-ended discharge is a viable routing for ASD
• R7 in unheated attic and R14 above roofline
CGSB Radon Control Options for New and Existing Buildings
“Radon-Reduction Guide for Canadians”, Health Canada-
Radiation Protection Bureau
“Illustrated User’s Guide to
Part 9 of the National Building Code 2010”
Indoor Air Research Laboratory
Indoor Radon Dilution: Air Tightness, Air Changes per Hour,
and Heat Recovery Ventilator
15
y = 3.9188e-0.244x
R² = 0.9994
0
0.5
1
1.5
2
2.5
3
3.5
4
0 1 2 3 4 5
Average SF6 Curve Fitting HRV#1OnHRV#2Off
MEAN Expon. (MEAN)
A two-storey single house of 1450 ft2 with 2 HRV units
y = 2.2565e-0.045x
R² = 0.9944
0
0.5
1
1.5
2
2.5
0 5 10 15 20
Average SF6 Curve Fitting HRV#1OffHRV#2Off
MEAN Expon. (MEAN)
y = 1.9022e-0.404x
R² = 0.9985
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5
Average SF6 Curve Fitting HRV#1OnHRV#2Off
MEAN Expon. (MEAN)
Tracer gas decay test
HRV#1 Off and HRV#2 Off, ACH =0.045
HRV#1 On and HRV#2 Off, ACH =0.244
HRV#1 On and HRV#2 On, ACH =0.404
Blower door test
0.79 ACH @-50 Pa
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A two-storey single house of 1450 ft2 with 2 HRV units
HRV#1 On and HRV#2 Off, [Rn] ranged between 17 and 74 Bq/m3, average 43.7 Bq/m3
HRV#1 Off and HRV#2 Off, [Rn] increased from 16 Bq/m3 to 222 Bq/m3 within 18 hours
HRV#1 On and HRV#2 On, [Rn] decreased from 120 Bq/m3 to 33 Bq/m3 within 4 hours
0
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Rn
(B
q/m
3)
Date and Time
Rn Concentration
HRV#1 ON HRV#2 OFF AG BSMT
HRV#1 OFF HRV#2 OFF AG BSMT
HRV#1 ON HRV#2 ON AG BSMT
HRV#1 ON HRV#2 OFF corentium BSMT
HRV#1 OFF HRV#2 OFF corentium BSMT
HRV#1 ON HRV#2 ON corentium 1st floor
Indoor Radon Dilution: Air Tightness, Air Changes per Hour,
HRV, and Radon
17
Illustrations courtesy of Natural Resources Canada (left) and Health Canada cross-Canada
radon survey (right)
Indoor Radon Dilution: HRV for Radon Control
HRVs suitable for houses are
airtight and with moderate radon levels
According to the Cross-Canada survey, >90% of
Canadian homes with radon issue have radon
concentration between 200 Bq/m3 and 600
Bq/m3.
A Combination of Strategies:
CCHT Semi-Detached Net-Zero Energy-Ready Smart Home
18
A sub-slab ventilation panel, a radon prevention membrane, an integrated drainage
system, 4 radon stacks
Extensive sensors for monitoring sub-slab pressure, soil temperature, stack flow/RH/T/V.
19
Future Work: 2018 and Beyond
• Database of building materials for radon control
• A field study of HRV for indoor radon control
• Radon cross-contamination through an ERV core unit
• Discharged radon dispersion (measurement from mitigated
homes and Computational Fluid Dynamics Simulations)
• Radon measurement and intervention in daycares/schools and
workplaces with elevated radon levels
• Soil gas sampling + indoor air/radon monitoring + building study
• Apply verified radon control products to new construction
2020
Thank you
Liang Grace Zhou
Senior Research Officer
613-990-1220
Liang.zhou@nrc-cnrc.gc.ca
www.nrc-cnrc.gc.ca
/
November is Radon Action Month in Canada!
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Outreach
• “Radon in Canadian Buildings”, Building Owners and Managers Association of Ottawa,
2012
• “Radon Mitigation NRC’s Indoor Air Strategies and Solutions,” for Association of
Municipalities of Ontario, 2013
• “Impact of Radon ASD System on Re-entrainment, Energy Use, and Indoor
Environment”, Construct Canada Expo, Toronto, 2013
• “New Research for Healthier Homes,” Better Builder Magazine, 2014
• Canadian Home Builders’ Association Housing Research Summary 2013–2015
• Host a stakeholder consultation workshop in 2012
• “NRC helps integrate radon technology into the building code”, Canadian Association of
Radon Scientists and Technologists, Vancouver, 2015
• “Experimental Study Of Heating Energy Use And Indoor Environment During Operation
Of Active Soil Depressurization Radon Mitigation System”, Indoor Air Conference,
Belgium, 2016
• “NRC and Radon Control Technologies”, Federal Provincial Territorial Radiation
Protection Committee 2016
• “NRC and Radon Control Technologies”, CHBA TRC Forum 2016
• “Combatting Radon with Scientific Research”, Construct Canada Magazine in 2017
• Media launch of National Radon Action Month 2017
22
Radon Control in A Large Building: a Case Study
Radon detector
with control
signal to HVAC
for outdoor air
intake 1 month energy data:
27% reduction in electricity consumption
>60% reduction in gas consumption
(Radon Environment Corp, Prince George case study)
Measurements should be made in each occupied (>4
hrs/day) room (basement and/or ground floor).
Large Federal Building in Northern BC:
Demand Control Ventilation
23
Material 1 2 3 4 5 6 7 8 9
Thickness
(m)2.54*10-2 1.52*10-4 1.00*10-3 1.00*10-3 2.54*10-2 1.50*10-3 2.70*10-3 2.70*10-3 5.08*10-4
D (m2/s) 2.25*10-7 8.05*10-12 2.10*10-11 2.03*10-11 2.89*10-10 8.58*10-12 1.04*10-11 1.12*10-11 --
RRn (s/m) 1.13*105 1.90*107 4.85*107 5.01*107 1.74*108 1.91*108 2.60*108 2.99*108 --
Receiving
Radon
(Bq/m3)
847872 198300 144311 109178 51362 49664 19448 10500 0