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

7

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

16

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