Radon Mitigation for Dirt-Floor Basement
I’ve bought a new house with somewhat high radon levels. Inspectors test, placed in basement, gave EPA protocol reading of 7.4 pCi/L. I’ve purchased an electronic meter and am getting comparable levels. I’m handy with DIY and plan to mitigate myself.
The house has a “day basement” (partially above grade, partially buried into a hillside), and two floors of living space above that. The basement already has a floor system of joists and plywood, slightly above grade; below that, on the soil, is a vapor barrier, but I’m not sure how good it is (are seams taped, etc).
I’m hoping I can simply ventilate the space between the vapor barrier and the plywood and achieve adequate mitigation. My plan is to run 4″ PVC from a hole in the plywood, put an inline fan, and vent out the side of the cinderblock basement wall (where the basement is above grade). Initially, at least, I don’t plan to pipe up to above the roofline. There is only one window anywhere near above the place where I’ll penetrate the basement wall, and it’s on the top floor (so about 20ft above where the vent will be).
My main question (other than is this likely to work, which I’ll find out and do more if not) is what kind of fan to use. I simply don’t know how much suction will be required. It depends mainly on the integrity of the plywood floor, I suppose. I could add a makeup air vent as well, and then I wouldn’t need much suction, but I’d be introducing outside air into the space under the plywood: that would be a heating load in the winter (I hope to finish the basement out into a rec room or something) and could introduce excessive humidity in the summer.
Here’s a simple drawing:
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