upgrading attic insulation


Old 01-21-04, 04:22 AM
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upgrading attic insulation

my house was built in the 50's. The attic has loose fill but I don't know what it is. There doesn't appear to be a vapor barrier under the insulation. Should I remove the old loose stuff, or just put fiberglass batts without vapor barriers on top? I am concerned that I don't know if the old stuff is flamable.
Also, if my attic is not heated, do i have to insulate the roof or just the floor?
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Old 01-21-04, 06:51 AM
Join Date: Nov 2001
Location: Taylors, SC
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If there is no vapor barrier, it likely is not worth the effort to remove the insulation to install one. The accumulated paint on the ceiling over the years probably provides sufficient barrier.

You can install batts without a vapor barrier over the loose fill. It may be easier to blow loose fill insulation over the existing loose fill. It certainly is cheaper.

It may be rock wool insulation. Fiberglass insulation will support some combustion, treated cellulose insulation ordinarily does not. The wood in the attic will all burn. I would not be too concerned about the insulation.

Insulation is typically placed between the heated space and the unheated space. Unless the attic will be heated for some purpose, the insulation will be applied to the attic "floor".

Hope this helps.
Old 01-22-04, 04:22 AM
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upgrading attic insulation

i want to put unfaced fiberglass insulation on top of the loose fill that's there, and i want the highest R value for my area.BUT there will be plywood sheets on top of where the insulation will go. If I put on, say R30, it will get squished when the plywood goes back on top. Should I get a thinner batt (lower R value), or get the R30 and squish it? I want the attic as insulated as possible.
Old 01-22-04, 05:44 AM
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Location: Bay Area, CA
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Insulation works because it has "dead air" spaces which slow the rate of heat transfer between the warm side and the cold side.

If you "squish" insulation, you reduce the "dead air" spaces and reduce the effectiveness (R value) of the batt.

Pick a thickness as close as possible to the uninsulated thickness of the ceiling joists and lay it in.

Will the plywood be something new in the attic? If so, make sure you don't block any soffit vents or you'll create moisture problems in the attic.

If you're going to attach the plywood with nails or screws, be careful of any wiring. Poking a nail or screw into a wire can be a "shocking" experience.

Don't close off any electrical junction boxes. Most codes require that they be accessible.
Old 01-22-04, 05:48 AM
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Old 01-24-04, 08:52 PM
Join Date: Sep 2002
Location: Michigan
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make sure you dont have Zonolite insulation (vermiculite)
asbestos ! loose fill !

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