Thermalstat!, by Chantal Keerak
Radon is a radioactive gas that is released by the decay of uranium found naturally in soil and rocks. When it is released into the outdoor air it is easily diluted and is no longer a concern. However, radon can often be drawn into the home, where it can build up to high levels and become a health concern. Exposure to high radon levels is the second leading cause of lung cancer.
The natural stack effect in a home will cause air from the outdoors to be draw into the lower levels of the home. As this air is heated, it rises and escapes out the upper levels. As a result, the air pressure inside the bottom levels of your home tends to be lower than that of the surrounding soil. If radon is present in the soil, it can be drawn into this area of lower pressure through places such as: cracks in the foundation walls or slabs, around utility penetrations, through floor drains or sumps, around window casings and along the foundation floor/wall joins.
In Revelstoke, the way homes are typically ventilated tends to contribute to the potential for radon to build up in our homes. Most homes in Revelstoke either have no mechanical ventilation, or have exhaust only ventilation such as bathroom fans. With no ventilation, the air in the home is less likely to be exchanged with fresh air as often as it should be. This can result in the accumulation of radon gas. With exhaust only ventilation, a vacuum is created sucking the radon gases into the home.
The Canadian guideline for radon content in indoor air was recently reduced from 800 Becquerels per cubic meter (Bq/m3) to 200 Bq/m3. A Becquerel is one radioactive disintegration per second. When inhaled, this radioactive disintegration causes small bursts of energy which can damage lung cells, and these damaged cells could potentially lead to lung cancer.
There is not a lot of data on the radon levels that are present in buildings in Revelstoke. We know of a few buildings that have been tested and the majority of the results have been over the 200 Bq/m3 recommended limit. Concentrations can vary significantly from home to home. It is possible for you and your neighbors to have almost identical homes but have very different radon levels.
Since radon is odorless and colorless the only way to know if it is present is to test for it. Testing is easy and inexpensive. The BC Lung Association has test kits that you can purchase for only $30 which includes the lab analysis fees. Kits can be ordered by calling 1-800-665-5864. Kits can also be purchased at many of the hardware stores but prices and types may vary. Radon concentrations in a home can vary significantly over time and with the seasons. Therefore tests that are done over a longer period of time will give a more accurate indication of the average radon concentration in a home.
If you find high radon levels in your home, don’t panic. There are many things that you can do to significantly reduce these levels, many of them being quite inexpensive. Some recommended measures are: the use of sealants to plug cracks and gaps in basement floors and walls, installing special flanges in basement drains, airtight covers for sumps, and sealing off any exposed soil. Adding a balanced mechanical ventilation system can also significantly reduce the radon levels in a home. Ideally this can be done by adding a heat recovery ventilator. Supplying balanced make-up air for your exhaust fans can also sometimes help. If the radon levels are still too high, installing a sub slab ventilation system that draws the radon out from under the slab before it can enter the home is the most effective radon reduction method.
When constructing a new home, low cost preventative measures such as: minimizing entry points for radon, ensuring adequate ventilation, reducing the negative pressure in a home and roughing in a soil depressurization system will help to reduce the chances of high radon levels.
The CMHC has an excellent publication called Radon – A Guide for Canadian Homeowners. This publication explains radon in detail, and will describe various ways to reduce radon in existing homes, as well as preventative measures for new homes. The publication can be found on their website at www.cmhc-schl.gc.ca/odpub/pdf/61945.pdf .
Chantal Keerak is a professional mechanical engineer. Her Revelstoke based company, VerdaTech Energy Management and Consulting BC, provides heating and ventilation system design and energy efficiency assessments for residential and commercial buildings throughout BC. She can be reached at 250 814-8719.