Tough new Health Canada recommendations on radon exposure may soon affect forming and foundation contractors, if proposed changes to the 2010 National Building Code take effect.
Tough new Health Canada recommendations on radon exposure may soon affect forming and foundation contractors, if proposed changes to the 2010 National Building Code (NBC) take effect.
Radon is a colourless, odourless gas formed in soil, rock and groundwater as radium decays.
“Recent scientific evidence has conclusively linked long-term exposure to high levels of radon to a higher incidence of lung cancer,” said Gary Holub, a Health Canada media relations officer.
“Health Canada worked closely with the Federal-Provincial-Territorial Radiation Protection Committee in making the decision to lower the guideline from 800 Bq per cubic metre to 200 Bq per cubic metre for all buildings, including homes. This new threshold places Canada among the international leaders for radon guidelines, so that Canada has one of the lowest acceptable levels for radon in buildings.”
The new guidelines were published in the Canada Gazette in June 2007.
“The construction of new dwellings should employ techniques that will minimize radon entry and will facilitate post-construction radon removal, should this subsequently prove necessary,” it said.
Radon isn’t usually thought of as a separate issue in building projects at the contractor level, noted Dave Hanneson, president of BIOMATION, an Almonte, Ont. company that sells radon testing equipment and provides training in its use.
“A foundation contractor may be required to place an adequate gravel bed underneath a concrete slab or use a particular type of air barrier to make a structure ‘radon ready,’ but in our training session with contractors, we don’t see a lot of prior knowledge about radon itself,” he said.
“The scientists aren’t talking to the contractors, so what they know is often reflected only in the building code.”
Last year, the Canadian Commission on Building and Fire Codes approved the creation of The Task Group on Protection Against Radon Ingress, which is currently discussing the proposed changes to the 2010 NBC.
“The consensus of the group is that, in the absence-of cross-Canada radon data, a code solution has to be applied to all buildings,” said Frank Lohmann, technical advisor, National Research Council — Institute for Research in Construction, Canadian Codes Centre.
Health Canada and Natural Resources Canada are in the process of creating a radon survey, which will take three to five years to complete.
Once finished, the radon map might help to identify the most affected areas and to recognize the scope of the problem in new and existing buildings.
Lohmann also noted that changes to the code will describe the type of construction necessary to prevent radon ingress, but won’t require builders to test the structures.
“Testing is the only way to know what the real risk is,” said Lohmann.
“But, testing isn’t meaningful during construction because the building envelope hasn’t yet been sealed. An adequate radon test requires between six weeks and three months to complete, so it isn’t practical or economical for builders to test for radon before occupancy.”
Proposed changes to the NBC include increased attention to wall and floor cracks, crawl spaces, building envelope penetrations, sump pits and floor drains, typical entry points for radon gas.
Most of the focus is on residential building envelopes.
The changes for houses and small buildings are more detailed, while those for large buildings are more performance-oriented because the design of larger structures involves architects, engineers and designers who specify ventilation, mechanical and air barrier systems.
The proposal essentially just adds radon to the list of issues the design has to address, said Lohmann.
The task group is also recommending further research that may include field testing of high-rise buildings.
“It is well understood what happens in buildings up to three storeys,” said Lohmann.
“In high-rise buildings, the stack effect, exacerbated by elevator shafts, generally leads to higher concentrations in the basement and bottom stories as well as the top story. But there is not much information on what happens in between four and 10 storeys.”