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rockyrr 07-07-2010 08:26 AM

Correct insulation?
 
We have an old house we use for a cabin. It has 1+ floors. That is, it has an "attic" with regular flooring 3 windows and guests sleep there (there are 4 beds). It has open rafters (you can see the actual roof wood that the shingles are nailed to). I'd like to insulate the interior roof between the rafters to make it more comfortable for guests in the summer. It does get warm up there. I'm thinking of some sort of foam (boards?) insulation rather than fiberglas. I'm assuming that since I'm not going to drywall over it, fiberglas may not be a good choice. Can any experts here give me some guidance?

Thanks,
Rocky

Wildie 07-07-2010 01:50 PM

Fibre Glass insulation is more economical! F/G and a 6 mil vapor barrier will keep the F/G from falling down.

What type of shingles are on the roof? Asphalt shingles cannot take much heat and so space must be allowed between the insulation so that air can circulate and cool the roofing.
A metal roof, will not deteriate from the high heat. Although, it may buckle.

rockyrr 07-07-2010 02:47 PM

Quote:

Originally Posted by Wildie (Post 466497)
Fibre Glass insulation is more economical! F/G and a 6 mil vapor barrier will keep the F/G from falling down.

What type of shingles are on the roof? Asphalt shingles cannot take much heat and so space must be allowed between the insulation so that air can circulate and cool the roofing.
A metal roof, will not deteriate from the high heat. Although, it may buckle.


It has asphalt shingles. Will the vapor barrier keep people safe from fiberglas?

Thanks

Wildie 07-07-2010 07:24 PM

Quote:

Originally Posted by rockyrr (Post 466521)
It has asphalt shingles. Will the vapor barrier keep people safe from fiberglas?

Thanks

6 mil plastic will not allow water to pass, so its unlikely that fibreglass particles will either.

Fibreglass particles aren't considered to be unsafe. Just very unpleasant.

Gary in WA 07-07-2010 08:22 PM

"Fiberglass is a suspected carcinogen and carries a hazard warning label. Cellulose is much more benign." http://michaelbluejay.com/electricity/insulation.html

You will probably need to cover plastic ---ask your LOCAL building department. Ask them if you even need it: http://www.ecohomemagazine.com/energ...gy-claims.aspx

http://www.buildingscience.com/docum...ecommendations

You may/not need to cover foam, ask them: http://www.icc-es.org/reports/pdf_files/NES/Ner699.pdf
Be sure to say the application.

Be safe, Gary

Wildie 07-07-2010 10:31 PM

Quote:

Originally Posted by GBR in WA (Post 466658)
"Fiberglass is a suspected carcinogen and carries a hazard warning label. Cellulose is much more benign." http://michaelbluejay.com/electricity/insulation.html

You will probably need to cover plastic ---ask your LOCAL building department. Ask them if you even need it: http://www.ecohomemagazine.com/energ...gy-claims.aspx

http://www.buildingscience.com/docum...ecommendations

You may/not need to cover foam, ask them: http://www.icc-es.org/reports/pdf_files/NES/Ner699.pdf
Be sure to say the application.

Be safe, Gary

Hi Gary, I would agree that cellulose is superior. In fact I had my home insulation bulstered with cellulose just recently.
The problem, as I see it, in this case would be to install it in the rafter cavities. Bats of insulation can be pressed into position. Although, from experience at my place, it tends to fall down if its not supported.
Here in Canada, warnings about fibreglass being a carcinagen are not given. Must be a US requirement.
My preferred choice of insulation is Roxul, spun rock bats.
Its R value per inch is superior to fibreglass and is fireproof.
Its commonly used here in Canada, but I'm unaware if its available in the US.
As for XPS insulation, we are required to cover it with something like drywall.

rockyrr 07-08-2010 06:31 AM

Folks, thanks for the feedback. It gives me much more info than I had.


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