The most efficient and effective method to mitigate radon in a residential setting is through Active Sub-slab Depressurization (ASD).
ASD involves creating a negative pressure (vacuum) under the basement concrete floor (slab) and continually venting the soil gas that is collected to the atmosphere where it rapidly dissipates. I like to describe it as “sucking the soil gas out before it can enter your home’s breathing space”. There are two main components to an effective and efficient radon mitigation: The system itself (pipe and fan), and sealing of the slab.
The system itself is made up of 3” or 4” schedule 40 ABS or PVC pipe and fittings, and a specialized inline radon fan. Generally, a hole is cored through the slab (suction hole) and another through the sidewall (exhaust hole) of the house. Some of the material under the slab will be removed through the suction hole to apply suction to a larger surface area. In Calgary and surrounding area, most homes have gravel under the slab which is porous and allows for easy airflow. Material such as clay, sand, and dirt can be more challenging to work with as they are harder to pass air through. As of 2016 homes in Calgary are required to have 100mm or 4 inches of clean gravel below the slab, and they often, but not always, do. The correct fan size can be determined once the major sealing is done by performing pressure field diagnostics using a micro-manometer. This is to ensure that a strong enough negative pressure is created to collect radon gas during all seasons and weather conditions. I will post a more in-depth blog on diagnostics at a later date. The pipe and fittings are solvent-welded together once measured and cut appropriately. In the vertical run of pipe between suction and exhaust, the radon fan is installed using flexible couplers which reduces vibration and allows for easy fan replacement should it be required later on.
The second component to a successful radon mitigation system is sealing openings in the basement slab. Sealing is important for an efficient radon mitigation system for a couple reasons: Firstly, the negative pressure will be lost between the suction point and the far reaches of the basement if there are openings along the way. Think about trying to drink through a straw full of holes. Secondly, leaving openings unsealed will result in an energy penalty to the homeowner as there will be conditioned (heated or cooled) air from the room pulled through the openings, collected with the soil gas and vented outside. When you are paying to heat or cool the air in your house you certainly do not want it being blown outside! There are also other risks to taking large volumes of air out of a house such as backdrafting and increased moisture ingress. The most common areas that requiring sealing include the base of the radon system at the suction hole, large floor cracks, sump lids, accessible areas where the slab meets the basement foundation walls, around floor drain plumbing, water main conduit, plumbing penetrations, and under the furnace if the original furnace was hung by the builder prior to pouring the slab.
A well sealed slab and a correctly sized radon fan, with properly routed piping in accordance with federal and local building codes and Canadian National Radon Proficiency Program (C-NRPP) will ensure a successful radon mitigation system with very minimal operating costs. The fans that I end up using quite often use less than 60 watts of electricity, which based on my last calculation was about $5 per month or $60 per year of electricity. Radon fans require no maintenance and are designed to run continually for their entire life. Fans usually last between 5 and 10 years however I know of one that has been operating for 13 years. Replacement fans are fairly affordable at under $300 for most residential units.
The location of your ASD radon mitigation system including suction location, pipe routing, exhaust point, required sealing, any potential challenges, and of course the cost can all be determined at the free, no-obligation site visit that I offer to homes in Calgary, Airdrie, Cochrane, Okotoks, and surrounding areas. Please browse the photo gallery under “Installations” for examples of various radon mitigation systems and their components or click on “Request A Free Quote” to book your free site visit. I love what I do and can’t wait to share my knowledge and expertise with you!
