Wade Paquin walks through his “bathtub detail,” a foundation insulation method that uses closed-cell spray foam beneath a concrete slab instead of rigid board. He explains that rigid insulation can shift during concrete placement, creating seams and thermal breaks, while spray foam forms a continuous, monolithic layer across the slab and up the foundation walls. Applied over compacted, washed stone, the foam bonds into the substrate, improving adhesion and stability. At typical thicknesses, it delivers high R-value performance while acting as a vapor retarder and radon barrier. Paquin details how the system integrates with rim board insulation to reduce air leakage, control moisture, and improve indoor air quality in basement construction.

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