This new project stems from a friend letting me borrow his radon tester. Looks like I'm over the threshold that requires mitigation. I haven't had the tester plugged in for a long time so I'm not positive on the exact concentration but thought sealing the space would be a good start whether I need to mitigate radon or not. Currently have a space with a dirt floor. There are two vents at either end, I open them in the summer, close them in the winter. Has 6mil poly laid over top, joints are overlapped but not taped. Edges are not taped to the concrete foundation walls. Foundation walls have white, rigid insulation glued to them (old school, not closed cell?). I insulated the rim joists but stuffing batt insulation in, cutting rigid polystyrene to size and spray foaming around the edges. I'd like to go through and seal it properly but not sure how to go about it on the walls. I've seen some links showing the rigid insulation installed first then vapor barrier run up the walls 6" - 12", sheeting held by strips of treated wood nailed/screwed into the concrete and then the top of the strips sealed with silicon or something. I've seen other links that show the plastic run up the walls, glued on with sealer and then the rigid insulation installed over top. What's the best way to do it? Should I be trying to tear off that white insulation and replace with the newer style pink rigid? Thanks for any tips/comments/advice!