Ask the Architect

The properly sealed house

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Q. We interviewed three contractors for a spring project, and one kept talking about switching to using spray foam insulation. Is it better because it costs a lot more? We aren’t sure it matters enough for the cost. Also, he said we need a “beefed up” water barrier because we live within a mile of the ocean. Is this true? Our neighbors all used fiberglass.

A. This may take more than one column to answer. First, exterior walls must meet four basic conditions with what are called “control layers.” Properly enclosed homes should have, from outside to inside, liquid control, air control, thermal control and vapor control layers. Not just one can lead to very costly problems. Eleven years later, one of my clients is spending $40,000 to rebuild wood stud walls on the north side of her home. She spoke with the contractor, who admits he made a mistake, but walked away since he was just retiring to Florida. Lots of anger there, but still a problem to solve that you can avoid.

Exterior house wrap is critical. You need a breathe-able (vapor-permeable) barrier. The best ones are sprayed or rolled on, but they’re more expensive because stapled sheets have openings at each staple and the staples rust, especially in salt air. I see it everywhere, though, and we only see the results when the siding is removed. Even though the exterior face of the plywood should be taped to reduce air/vapor movement, I see it rarely done, also. Where you need a completely water-resistive adhered barrier is where the concrete foundation wall and the wood stud wall meet, overlapping at least 12 inches up and down from the joint. Many people told me they saw water coming at these points during the Sandy flooding. Door sills and around the frames of doors and windows is also necessary.

Complete waterproofing at these joints is critical, yet that form of water-sealing has met with dismissal by the New York Rising program, which has repeatedly denied this simple detail in the “mitigation” process. Maybe, if enough people complain, they’ll change their minds. Then we can call it New York Up-Rising.

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