Slab Edge Insulation (or lack thereof)
Cold edge of Zone 4. When I built my house a couple of years ago, I didn’t understand the purpose of slab edge insulation as explained by the sub doing the foundation waterproofing. It was “optional” as the energy code is not enforced around here. Fortunately, I came to understand it before the slab went in so, along the back walkout wall, I had R-10 board laid horizontally at a 2 ft width instead of vertically.
My neighbor built at the same time with the same custom builder (who never advised us about slab edge insulation). As we are now just past a couple of weeks of record sub-zero temperatures, I was talking to my neighbor. The base molding on the back drywall of their walk-out basement built up ice dams during this period. I had no such problem with the same basic design and materials. I also have a 15 mil vapor barrier compared to their 6 mil and better insulation.
Unlikely my neighbor has slab edge insulation. Would this explain the situation? What can be done at this point? Would installing 2 inches of foamboard 2 feet deep on the outside of the foundation do the trick? Thanks.
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