Insulation

Published on August 30th, 2012 | by Henri

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Sealing holes after blowing in insulation

Q.    I enjoy you column and rely on it for my many household projects. I need a quick response as a contractor is coming tomorrow to have a contract signed on blowing in cellulose insulation to the exterior walls.

The contractor is adamant in his opinion that the treated cellulose does not need to have the drill plugs replaced, maintaining that the opening provides space for the insulation to breathe. He agreed to use duct tape over the holes if I insisted, which I think I will.  Another insulator who gave me an estimate said that about 50% of his jobs, when working for remodeling contractors, replace the plugs and the other 50% leave it open.

The house is covered by vinyl siding, which should prevent any water getting in, but I am concerned that they will be drilling through the existing rigid foam insulation and the black liner paper that was put in below the siding. The house is approximately 50 years old, has virtually no wall insulation except for the half-inch thick rigid foam sheets that went in when the siding was installed eight years ago.

A.    Vinyl siding is not watertight, and neither are most other sidings, so there is a risk of water getting into the walls. Sealing the holes with duct tape will make them watertight, which contradicts what the contractor says about the walls needing to breathe. A better way to seal the holes is to tape pieces of Tyvek to the rigid insulation over them. This will keep water out and allow vapor to exhaust if it needs to.

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