How sub-slab depressurization works
Active soil depressurization is a common radon mitigation method. A certified mitigator can assess whether it suits the home and explain the proposed pipe and fan route.
The system aims to draw soil gas from beneath the slab and vent it outdoors. The required suction, fan and pipe arrangement depend on the home and should be checked after installation.
Health Canada describes active soil depressurization as an effective method. Installation time and reduction vary by home; follow-up testing confirms the result.
What else goes into a good install
Sealing helps the fan do its job. Common add-ons are a sealed, gasketed sump lid, sealing major floor cracks and the gap where the floor meets the wall, and a membrane over any bare-earth crawlspace.
Pipe routing depends on the home and system design. Ask the mitigator to mark the proposed route and explain any effect on finished areas or an existing rough-in.
The work should follow the Canadian standard for existing homes, CAN/CGSB-149.12, Radon mitigation options for existing low-rise residential buildings. Health Canada recommends a mitigator certified by the Canadian National Radon Proficiency Program (C-NRPP). Ask to see the certification.
Ask for a simple pressure gauge on the pipe, such as a U-tube manometer, so you can see at a glance that the fan is pulling. Ask the installer to show you how to read it.
What affects the price in Ottawa
Costs depend on the home, system design and provider. Ask for an itemized written quote, including applicable tax.
Costs vary with the property, testing method, system design and provider. Ask for a current itemized quote and confirm what testing and follow-up are included.
Costs vary with the property, testing method, system design and provider. Ask for a current itemized quote and confirm what testing and follow-up are included.
Costs vary with the property, testing method, system design and provider. Ask for a current itemized quote and confirm what testing and follow-up are included.
The price moves with the pipe route, how many suction points the slab needs, the floor finish, and whether the pipe goes outside at the wall or up through the house.
Two houses that look alike can price differently. A slab poured over tight clay may need more suction than one over gravel. The fan uses a small amount of electricity year round. Ask for the fan model and its wattage so you know what you are signing up for.
The retest after
Follow-up testing is needed to measure the system’s effect. Health Canada recommends a long-term retest during the first heating season after installation, ideally in the same location as the original test.
A short check after installation can provide an early indication of system function. It does not replace the long-term retest.
Health Canada recommends retesting homes with active mitigation systems every five years, and sooner in certain circumstances after changes to the home or system.
Living with the system
Check the system indicator at the interval the installer recommends. If it differs from the normal operating mark, contact the installer and ask whether further testing is needed.
Keep the sump lid sealed and put back any caulking you disturb during other work. Do not block the exhaust outside with snow or storage.
Keep the original test, installation details and follow-up results together for future maintenance or a property transaction.
If a representative long-term retest remains above the guideline, ask a certified mitigator to assess the system and propose corrective work under the written agreement.
Questions to ask before you hire
Are you C-NRPP certified for mitigation, and can I see the certificate number? Will the install follow CAN/CGSB-149.12?
Where will the pipe run, where will it exit, and what will I see inside and outside the house? Will you seal the sump and major cracks as part of the price?
Which fan will you use, and what is its warranty? What is your own warranty on the system, and does it cover a retest that comes back high?
Is a short test after installation included? Who supplies the long-term retest kit for the next heating season?
Get the answers in writing on the quote. Compare quotes on what is included, not only on the total.