Reducing Radon: What Actually Works — From Free Fixes to Mitigation Systems
If your radon level is too high, here’s the good news: it can almost always be lowered substantially — often starting with simple steps. Here are the options, from least to most effort.
Free and immediate: ventilate properly
Regular, thorough airing dilutes the radon concentration — open windows wide several times a day, especially in bedrooms and on the lowest lived-in floor. It’s not a permanent fix for seriously elevated levels, but it lowers exposure right away. One caution: don’t leave basement windows permanently cracked when the basement is colder than the house — that can strengthen the stack effect that pulls radon out of the soil in the first place.
Seal the entry points
Radon enters wherever the building touches the ground and isn’t tight. Typical weak spots:
- cracks and joints in the slab and foundation walls
- pipe and cable penetrations
- sump pits without sealed covers
- dirt floors and unsealed crawl spaces
Sealing with flexible caulk, fitting a sealed sump cover, and putting a proper vapor barrier over a crawl space floor often helps a lot — especially when a few entry paths dominate.
Change the pressure: the method that works best
For clearly elevated levels, the most reliable solution is to keep radon from entering at all. Active sub-slab depressurization — a pipe through the slab and a small inline fan that vents soil gas above the roof — is the standard mitigation system in North America. Installed by a certified mitigation contractor (NRPP/NRSB listed), it typically costs $800–$2,500 and routinely cuts levels by 80–99%. Balanced ventilation systems (HRV/ERV) can help as a complement.
Building new? Prevention is almost free
In new construction, radon protection costs next to nothing: a sealed, continuous slab, sealed penetrations, and — in radon-prone zones — a passive vent pipe roughed in under the slab that only needs a fan added later if tests come back high. Many U.S. jurisdictions already require radon-resistant construction; ask your builder about it early.
Afterwards: retest
Every measure is only as good as its measured effect. After the work is done, test again — ideally with a long-term test over the next heating season, and every couple of years thereafter.