Vapor barrier


Old 12-04-00, 08:58 AM
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Our 1930's Wisconsin home has had some insulation updates, but is in need of more. Exterior walls had cellulose blown in and attic floors were blown w/ a scant amount of fiberglass. Some time ago I read an article that all these older homes who have had empty ext. walls filled w/ blown-in product have been done a disservice by the insulation contractor. W/ out a vapor barrier, as with new construction, the insulation will at least be less effective due to moisture build-up, & at worst your home's framing will suffer from rot. We're committed to this house & have remodelling plans started, but a little concerned about this insulation query. Any advice is sincerely appreciated! Thanks.
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Old 12-04-00, 10:49 AM
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J Andrew wrote:

< more. Exterior walls had cellulose blown in and attic floors were blown w/ a scant amount of fiberglass. Some ti >

Since your walls are finished, and you do at least have insulation in them, focus on your attic. Heat(and condensation's) greatest propensity is to rise, so take the following steps to tighten up you heating budget this year:

You mentioned a scant amount of fiberglass in the attic - is this no more than 2-3 inches? Also, do you have lots of decking up there?

Once that's out of the way, there's a simple process to adding vapor-barrier faced insulation to the attic plane. You may either spray down a vapor barrier, or, add faced batts of fiberglass. Judging by your location, you'll need at least R-40, so get at least R-30 fiberglass.

Remove two or three bays(stud widths) of blown insulation, just throw it into adjacent bays. Lay the vapor-faced fiberglass face down, toward the living areas of your home.

Shovel the loose stuff back on top of the batts, and this should give you close to the R-40 you'll need up there. Scoop out the next two or three bays, and work your way across the attic.

Keep an eye out for any utilities sticking up through the attic surface(junction boxes, conduit running here and there, fan boxes, etc). You should keep insulation at least three inches away on either side from fan motors or recessed ceiling light fixtures.

Good luck, and a very toasty holiday!


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