The principle
Radon enters a building because the soil gas beneath it is at slightly higher pressure than the air inside, so it is drawn in through every available opening — cracks, the sump pit, floor drains, service penetrations, the perimeter joint.
Sub-slab depressurisation reverses that pressure relationship. A pipe is installed through the floor slab into the aggregate beneath it, connected to a continuously running fan that draws soil gas out and vents it above the roofline, where it disperses harmlessly. With the space under the slab held at lower pressure than the building, the gas goes up the pipe rather than into the basement.
What installation looks like
Most residential installations are completed in a day. Alberta’s building code has required a radon rough-in in new residential construction for over a decade, which makes retrofitting substantially simpler in newer homes — much of the pipework path already exists.
- A diagnostic assessment of the foundation, sub-slab material and likely entry points
- A core hole through the slab, usually in an unobtrusive location
- Pipework routed to the exterior or up through the building to above the roofline
- A continuously running fan, typically mounted outside the conditioned space
- Sealing of major entry routes — sump lids, visible cracks, the perimeter joint
- A monitoring gauge so the system’s operation can be checked at a glance
- Retesting after installation to confirm the result
Retesting is the part people skip
A mitigation system is a piece of equipment with a designed effect, not a guarantee. Installations vary in effectiveness depending on the sub-slab conditions, and the only way to know the system achieved what it was designed to achieve is to measure again afterwards.
Systems also need occasional attention over their life. Fans fail, and a failed fan on a system nobody checks means the building has quietly returned to its pre-mitigation state. The monitoring gauge exists for exactly this reason, and checking it is a reasonable item to add to a recurring property visit.
Who performs it
Design and installation should be carried out by a C-NRPP-certified mitigation professional. VacantHomes.ca does not design, install or service mitigation systems; where one is needed on a property under monitoring, we coordinate the engagement, attend for access and record the work against the property.