Vapor retarders

Published on November 16th, 2015 | by Henri


Adding insulation to 1950s ranch

Q.    We are trying to make my mother’s 1950s ranch home in Massachusetts more energy efficient. I have heard having cellulose insulation blown into the walls is a good and energy efficient idea, but also read that since there may not be a vapor barrier behind the walls it could lead to moisture problems. I would appreciate any suggestions you may have so we can best address the situation. (We are intending to add adequate attic insulation to the house.)

A.    Cellulose is indeed a good retrofit insulation, and it is made of recycled materials – newsprint. You can provide a vapor retarder by making sure that all possible bypassing avenues that would allow warm, moist conditioned air to enter wall cavities are sealed.

Small cracks around window and door trim, baseboard and any ceiling molding may be caulked with a paintable caulking compound. Also check ceiling and wall-hung fixtures.

Electrical switch and receptacle boxes can be made tight by fitting them with closed-cell foam gaskets, available in hardware and building supply stores.

The best type of caulking is polyurethane, which you should be able to find in construction specialty stores. You are unlikely to find polyurethane caulking in hardware and regular building supply stores, but it’s worth a try. Home Depot carries Sika construction adhesive and sealant in their masonry section – not in their paint section, where they carry the usual array of popular caulking.

Once all potential bypass avenues have been sealed, prime the walls with B-I-N and paint them with two coats of your choice of a quality latex paint. You can also carry the same treatment to the ceiling.

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