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How We Solve Your Radon Problem

The gold standard for Radon reduction is what’s known as a Sub Slab Depressurization System, or an SSDS for short. Developed initially in Elliot Lake, Ontario, where Radon was first addressed as a carcinogen in homes in Canada (similar research was being done in Grand Junction, Colorado, at the same time) by Arthur Scott, SSDSs are now used everywhere to combat Radon!

Radon gas in the soil enters the house due to less pressure inside the house than in the soil. This effect draws in soil gasses that contain Radon. This is for several reasons, including the stack effect and soil displacement. An SSDS creates a more significant negative pressure underneath the slab than the pressure in the house. Thereby capturing the Radon before it has a chance to enter into the house. It is then exhausted outside, where it can then dissipate with outdoor air.

If there are large openings such as sump pits, interior French drains, bathtub rough-ins, or some floor drains, these need to be sealed up, both to prevent Radon from coming up and also to ensure that the SSDS fan is drawing air from the soil, not from the house. Areas like crawlspaces typically need more work and attention, but the basics are the same: seal them as best as possible and draw air from them to put the space under negative pressure.

If you’re researching online, you may find pictures of Radon systems with the fan outside the house and the discharge pipe going up the exterior wall to above the roofline. This is the original design for a mitigation system and is extensively used in the USA. The idea is that the fan and all the pressurized parts of the mitigation system are outside the building envelope. The downside is that the air being moved through the system is typically at 100% humidity and can slowly freeze solid during frigid days in winter. When Health Canada wrote their guidance, they tested to see if that risk could be eliminated. As fans, piping, and procedures have become much better and more robust, the risk of leakage of pressurized pipe has become negligible. With this evidence, Canada’s guidance has the fan inside the house. The other risk they wanted to see was for discharge location. After building a mitigation system in their test houses in the National Research Center compound, they set up several testing rigs in and around the exhaust plume. They discovered that they were back to background radiation levels three feet from the end of the pipe, even directly across from the opening.

When we arrive at a house to install a mitigation system, we start by rolling out the red carpet. We lay a red carpet between where we plan to come into your home and where we work. We use many glues, chemicals, and sealants that are aggressive to types of vinyl, urethanes, and carpeting, as well as dirt, water, snow, or other debris we may be tracking in with us. We find it much better to roll up the carpet on our way out rather than potentially not clean everything up perfectly at the end of the day.

Once we are in the house, we look for a few things. We find a good exit point, one that discharges away from air intakes, decks, or other used outdoor spaces. This is either in a mechanical or unfinished space or as unobtrusive as possible. We love to use mechanical rooms, utility closets, or storage rooms to install systems. Rooms like cold cellars are typically outside the building envelope and do not make for effective mitigation system locations. We also look for openings between the house and the sub-slab, such as cracks, wall-floor joints, or sump pits that will make the system less effective and need to be sealed up.

Next, a communication test is performed. This tells us what fan size is required to draw air from the entire footprint underneath the basement slab to our main suction point to be exhausted outside. We use an engineered dust capture system to ensure that we are as clean as possible and that no additional work is required to clean up after we core a 5” hole through your basement slab. We then find an unobtrusive spot at or near the opposite end of the basement. Usually, a section of carpet that can be peeled back, a closet, or under something that likely won’t be moved. We then drill a ¼” or pencil-sized hole through the floor to set up our micromanometer, which is a highly accurate pressure gauge. Our vac then applies suction to our main draw point that we have cored, and we can see how much pressure we have at that ¼” hole. The vac can then be adjusted to mimic several different fans until it is set at the correct size. We then read the pressure and airflow off our diagnostic tube and ensure we have the right fan size for your house.


While it is always possible to install a large fan on every house, that leads to excessive noise, energy draw, and potentially back-drafting traditional combustion appliances. The most significant risk, however, is that there is no confirmation that this fan or suction point would solve the problem. It is entirely possible that the fan will not be able to draw the air across areas such as a footing wall or through tight soils such as clay or packed sand.

Once we have the correct fan size and design for the system, we finalize the pricing and draw up a contract specific to the job, with the final step being to install the designed system for your home.

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