Since radon is coming from the dirt below your basement floor, it would make sense that sealing any air-passageways between the sub-slab and basement air will help reduce radon levels. Unfortunately, that’s not the case. In several studies, sealing of cracks and sump lids reduced radon for about 1/2 day. Within 48 hours, levels were right back where they started. But why?
First of all, radon can penetrate many materials; it actually goes THROUGH them. Concrete is porous, meaning radon can easily pass through cement. Secondly, the concept of sealing those cracks and holes is to reduce energy loss…not to reduce radon. There’s a lot of misinformation online, so these ‘partial truths’ continue to be recirculated.
Radon enters the home’s ‘envelope’ when pressure in the house is lower than below the slab. When your home is under negative pressure (99% of homes are under negative pressure), the air escaping the home (combustion air appliances, bathroom fans, stack-effect through the attic, dryer vents, etc) must be made up from somewhere. Think of the inside of your home as the inside of a balloon…you can only suck so much air out without allowing new air in. This means it will be drawn through every little nook and cranny, as well as right-through materials like the concrete that your home is built upon.
Traditional radon reduction systems use “SSD” Sub-Slab Depressurization. By sucking air out of the space below your slab continuously with a radon fan, we negatively pressurize the sub-slab airspace. If we create more negative pressure below the slab than exists in the basement, the radon-laden air will follow the path of least resistance (to the radon fan) instead of seeping into your basement. The reason we seal the cracks and holes is so that the conditioned air is not sucked down into the sub-slab area and exhausted outside. This is not only a waste of energy, but further depressurizes your basement airspace.
So, sealing cracks and holes does indeed help, but not in the way that many imagine. Leave radon-removal to the pros at Akron Radon and we’ll take the guesswork out of successful mitigation!