Insulating Attic

columbusguy1November 22, 2010

I would like some advice on insulating my attic--problem is, the way it is now, there is precious little access to the underside of the roof!

My house was built in 1908, a foursquare (yucky term) with a hipped roof and three dormers and two chimneys. I have the original box gutters on all four sides, and the interior from the floor up the knee walls and entire ceiling is plaster and lath which is original. The roof sheathing is boards spaced about 1-2" apart, with several layers of asphalt shingles over that.

The area is one large room with storage in the kneewall areas on three sides, the fourth corner has a chimney going through it and no access at all--although my late cat had gotten in there by going under the windows in the dormer! She came out when I called her and shone a flashlight along the storage area floor.

I have seen Mike Holmes use spray foam on roofs, but I won't tear down my plaster to access it--what about blowing in cellulose? Since there are and never have been any vents in either the soffit or roof, I can't image rot being a problem--the rafters and boards visible in the storage areas look fine--I'm thinking those baffles aren't necessary.

Any advice? I'd like to blow in cellulose into the ceiling area and the knee walls...the rest of the house has had cellulose blown in for almost twenty years now.

Here is an exterior pic of the house.

Here is a link that might be useful:

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Oh, there is no heat up there except for a space heater when I need to use the space--my books are all stored up there. :) Some day, I may build shelving around the perimeter.
Also, there are no gaps at the tops of the house walls that I have found.

    Bookmark   November 22, 2010 at 10:42PM
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Blowing in insulation while continuing to use the space for easily accessible storage--let alone heating it--are incompatible uses.

Your choice is to consider the space either vented or unvented and proceed from there.

Vented is much easier. In that case, you have to airseal the ceiling as much as possible from the attic, though no vapour barrier is necessary in your climate. At the same time, you have to provide proper ventilation--on a 1:300 ratio for the attic. Then you can blow in all the cellulose you want. But storing anything there will be the equivalent of putting it outside. Definitely not a good idea for books!

For an unvented approach, you have to consider the attic part of the conditioned space of the home. In that case, the roof will have to be as sealed as much as possible from the exterior climate. Those 1"-2" gaps on the roof board won't do. Insulation will be at the top of the attic ceiling--usually a combination of foamboard and closed cell spray foam.

In either case, if the chimney is in use, you will have to simultaneously protect the framing from heat and fire hazards and insulate the space around it.

Here is a link that might be useful: Understanding attic ventilation

    Bookmark   November 23, 2010 at 2:33PM
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