How do I insulate uneven stone basement walls in a rehab row house in Philly?

Question

How do I insulate uneven stone basement walls in a rehab row house in Philly?

Asked by Alden Blyth

We are meeting the requirements for certification for LEED for Homes. We tried to insulate with blankets, but the air space behind the blankets allowed condensation to form and drain water to the floor. The wall surface is not smooth.

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Answers

Polly Osborne, FAIA, LEED AP's picture

My first thought would be to use a semi-rigid spray foam, such as Icynene. The foam sprays on, preventing infiltration-causing voids if done correctly, but the surface allows moisture to go through it because it is porous. The company claims that the moisture will not cause mold or rot the insulation.

If your stone foundation is not decorative or you can do it subterranean-only, then waterproofing it from the outside is preferable to allowing the moisture to infiltrate in the first place. For that I would use a system that includes waterproofing, drainage board and a filter fabric such as Miradrain. It is important to install these systems exactly as required by the manufacturer or you can destroy the waterproofing capability.

An alternative to completely waterproofing would be a gravel drainage channel with a perforated pipe or "french drain."