NRC and Radon Control Technologies

Transcription

1 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

2 Background HC-RPB cross-canada survey of 14,000 homes: ~7% of Canadians living in homes with a radon level >200 Bq/m 3 16% lung cancer deaths attributable to radon exposure 3,200/yr in Canada

3 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 How Federal Funding-Taking Action on Air Pollution Interdepartmental agreement with Health Canada Radiation Protection Bureau Fee for Service contracts with industrial clients NRC s multidisciplinary expertise, unique facilities, and links to industry Canadian Construction Material Centre and National Building Code 3

4 Radon in the National Building Code of Canada: Housing and Small Buildings 2015 NBC Part 9 Sealed soil gas barrier (e.g. 6 mil polyethylene based on CAN/CGSB 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

5 Radon in the National Building Code of Canada: Large Buildings & Optional for Small non-residential 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

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 6

7 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

8 Prevent Soil Gas Entry: Radon Diffusion Test Chamber Material evaluation ISO/TS : 2017 Test Procedure Air leakage test Phase of non stationary diffusion Phase of stationary diffusion Data post-processing and analysis 8

9 Radon Diffusion One-dimensional transient governing equation for radon diffusion D 2 C x,t x 2 λc x,t = C x,t t Where D, is the diffusion coefficient (m 2 /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. 9

10 Is Radon Diffusion Coefficient a Suitable Performance Indicator or NOT? Generally, materials with higher D are considered more permeable to radon. Receiving Thickness Material D (m (m) 2 /s) Radon (Bq/m 3 ) * * * * * * 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. 10

11 A New Approach to Assess Radon Barriers Radon Resistance R Rn (s/m) (Jiranek and Svoboda, 2017) Where d is the thickness of the material (m), λ is the decay constant (1/s) 11 R Rn = sin h λl d l l is the radon diffusion length in the material (m) Material Thickness (m) 2.54* * * * * * * * *10-4 D (m 2 /s) 2.25* * * * * * * * R Rn (s/m) 1.13* * * * * * * * Receiving Radon (Bq/m 3 ) 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 (Illustration courtesy of Health Canada) Canada US 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 Radon Mitigation Options for Existing Low-Rise Residential Buildings 12

13 ASD: Impact on Heating Energy Use and Soil Temperature Performance of Passive Radon Stack Canadian Centre for Housing Technology Expected Test House Daily Energy Consumption (MJ) ASD with Ground Exhaust (2012) ASD with Roof Line Exhaust (2012) Increased Daily Consumption (MJ) Increase, % 6.5% 4.2%

14 ASD: Stack Insulation, Backdrafting from Combustion Appliances, Gable-ended Discharge Indoor Air Research Laboratory 14 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

15 Indoor Radon Dilution: Air Tightness, Air Changes per Hour, and Heat Recovery Ventilator A two-storey single house of 1450 ft 2 with 2 HRV units Average SF6 Curve Fitting HRV#1OffHRV#2Off Average SF6 Curve Fitting HRV#1OnHRV#2Off Average SF6 Curve Fitting HRV#1OnHRV#2Off y = e x R² = y = e x R² = y = e x R² = MEAN Expon. (MEAN) MEAN Expon. (MEAN) 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 Pa 15

16 Rn (Bq/m3) Indoor Radon Dilution: Air Tightness, Air Changes per Hour, HRV, and Radon A two-storey single house of 1450 ft 2 with 2 HRV units 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 /12/17 14:24 7/12/17 13:12 7/12/17 12:00 7/12/17 10:48 7/12/17 9:36 7/12/17 8:24 7/12/17 7:12 7/12/17 6:00 7/12/17 4:48 7/12/17 3:36 7/12/17 2:24 7/12/17 1:12 7/12/17 0:00 7/11/17 22:48 7/11/17 21:36 7/11/17 20:24 7/11/17 19:12 7/11/17 18:00 7/11/17 16:48 7/11/17 15:36 7/11/17 14:24 7/11/17 13:12 7/11/17 12:00 7/11/17 10:48 7/11/17 9:36 7/11/17 8:24 7/11/17 7:12 Date and Time HRV#1 On and HRV#2 Off, [Rn] ranged between 17 and 74 Bq/m 3, average 43.7 Bq/m 3 HRV#1 Off and HRV#2 Off, [Rn] increased from 16 Bq/m 3 to 222 Bq/m 3 within 18 hours HRV#1 On and HRV#2 On, [Rn] decreased from 120 Bq/m 3 to 33 Bq/m 3 within 4 hours 16

17 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/m 3. Illustrations courtesy of Natural Resources Canada (left) and Health Canada cross-canada radon survey (right) 17

18 A Combination of Strategies: CCHT Semi-Detached Net-Zero Energy-Ready Smart Home 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. 18

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 19

20 Thank you Liang Grace Zhou Senior Research Officer / November is Radon Action Month in Canada! 20

21 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 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

22 Radon Control in A Large Building: a Case Study Large Federal Building in Northern BC: Demand Control Ventilation 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). 22

23 Material Thickness (m) 2.54* * * * * * * * *10-4 D (m 2 /s) 2.25* * * * * * * * R Rn (s/m) 1.13* * * * * * * * Receiving Radon (Bq/m 3 )