Hello all, Assuming our ICF home is well sealed, how much air will a Radon fan really pull? I would assume most of the make up air will come from window and door leaks. We have a poured concrete roof as well but with a wood frame stairwell for roof access. Patrick T

Radon fan is in the pipe that goes from under your ground/basement slab to the be vented out the roof. The cement pad is supposed to be sealed/caulked (perimeter and saw-cuts) with plastic under slab. It should be pulling air from the ground by design. With a craw space just has the plastic I believe with some rock.

The inside air it pulls should be minimal. There is usually a manometer to verify it is creating a neg pressure under the slab.

The amount of air it pulls from your HOUSE depends on how leaky the seams, edges and penetrations of your slab are. With slabs poured over 6" of clean gravel the air volumes it pulls through the soil can be surprisingly high, but irrelevant. The key is to interrupt the path of radon from the soil into your house through those slab and foundation wall leaks, vacuuming it out and sending it away.

Guessing the particle doesn't go through PVC? I would hope. Or through concrete?

Radon can mitigate through pores in concrete. Poly/EPS are effective barriers.

It takes QUITE a bit of time for radon to migrate through a 4" concrete slab, even longer if there's a vapor barrier under the slab. Radon in basements is primarily an issue of the foundation & slab not being truly air-tight. Cracks in the slabs and the seam between the slab & foundation wall can be sealed with self-leveling polyurethane caulk. With ICFs using a heavier-bodied (not soupy-self-leveling) decent quality caulk to seal the seams of the first 3-4 lifts of ICF foam prior to installing the finish wall can often make a difference in overall air tightness.

The alpha particle emissions of radon decay (the actual ionizing radiation) gets through PVC much more readily than through the concrete, but the only emissions you really care about are when the radon decays while in your lungs, not so much when it decays under the slab or in the vent pipe.

Good story on how radon in houses was figured out.

http://www.mcall.com/news/local/southernlehigh/mc-pa-radon-professor-history-20150127-story.html