EPA protocol dictates that all basement floor cracks be caulked with polyurethane caulk when a house is being mitigated for radon. This is not, as you might think, to keep radon and other earth gasses from entering the home following mitigation. Properly executed, mitigation turns the sub-slab under the basement floor into a vacuum, making it nearly impossible for gasses to enter living spaces through such cracks. Instead, the cracks are sealed to prevent the house’s conditioned air from leaving through these cracks.
Why would this be a problem? Because on the average, air flows through a mitigation system at a rate of nearly 100+ cubic feet per minute. If the cracks are not sealed as they should be, conditioned air is pulled through them and expelled outdoors. And that can add up to higher heating and cooling bills – an average of $600 a year or higher, according to the latest EPA estimates, or $50 a month! 50% of all the homes we have mitigated have increased vacuum rates after caulking cracks, relating to 10-20 cubic feet per minute... about 1/4 to 1/2 the rate of running a typical bathroom fan full time!
How can you tell if the cracks in your basement floor are leaking?
In many cases, it’s easy to tell because they can be very large. Huge exit points can be created by expansion joints, especially ones that were cut into the floor after the cement was poured, as well as by perimeter cracks where the wall and floor meet. If you add up the square footage created by an 1/8” crack that runs around the perimeter of your basement floor, then fold in the square footage of cracked expansion joints, it can be the equivalent of a gaping hole two-to-four-foot square!
There are other ways to detect leaking cracks. For example, although it’s not always present, black staining is a dead give-away even in newer homes; it’s caused by humid earth gasses swirling along the crack. If you see such staining, rest assured that any cracks left uncaulked by your mitigator would be an expensive oversight. After all, if the gentle pressure associated with earth gasses was able to force gasses in through those cracks you can be sure that your mitigation system will pull conditioned air out at a much higher rate.
Bottom line: If you’re considering a radon mitigation, insist that the quote cover caulking of all cracks per EPA/ASTM protocol.