Basement insulation, moisture, and radon
I am looking to insulate my 1986 house’s vintage poured concrete crawl space, but I need guidance! The house is located in zone 6A, right on the border of 5A. See the attached photo for the cross-sectional details of the house.
The entirety of the crawl space is below grade and is unused space. The goal of this project is to minimize the moisture, cold air, and radon into the house. It has an opening with a bilco door.
– Very high humidity in the space in the summer, which requires constant dehumidification.
– Space is about 35-45*F in winter, which likely affects the comfort of liveable space in the house.
– Radon levels in excess of guidelines
My thought is to add dimple mat to the floor to allow air/moisture movement should water ever intrude from below-grade, it could potentially move towards the floor drain. The next level would be to add foam-board or equivalent insulation to the walls and above the dimple mat on the floor. Next, I would have a vapor barrier cover all of these surfaces. I am unsure where I would terminate the vapor barrier, given that the first-floor framing is bolted into the concrete foundation wall, and not resting on top. Would I tape it just below that framing? The final step would be to buck out and build a weather-sealed door for the bilco entry through the foundation.
My thought would be to then keep the dehumidifier in the space as a back-up to keep the space within reason. The dimple mat would allow for a passive or active radon system if the vapor barrier alone does not reduce it to acceptable levels.
Does my logic make sense? Thanks!
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