Insulation confusion


Old 07-01-02, 09:30 PM
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Insulation confusion

The builder of our home insulated the exterior walls in the unfinished portioned of the house. They used unfaced R-13 batts with a silver paper covering entire walls. We were warned several times by the builder's rep to remove the silver paper before we sheetrock the walls. The exterior walls are covered on the exterior with LP type siding. There is no house wrap or plastic vapor barrier.

Some of the batts have been damaged and need to be replaced. The "Expert" at Home Depot said that the walls need to have a vapor barrier installed. He recommended that I replace the unfaced batts with faced ones.

If I replace all of the wall insulation it will add another $180 to the project and result in a 1 week delay.

What purpose does the silver paper serve?
Should I have left it there?
Does all of the insulation need to be replaced with faced batts?
Why did the builder use unfaced insulation?
Can I mix faced batts with unfaced batts?
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Old 07-02-02, 06:16 AM
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The silver paper you are refering to is probably a vapor barrier. There should be some instructions on it explaining how to install it and ratings. The builder's rep is probably referring to a manufacturer's information. If there are rips or tears in the silver paper you could tape them and you can get it at HD.

I'm pretty sure in your area you have a lot of rain fall per year and your winters are not that severe. This makes it difficult for me to advise you on the proper applicatiion of a vapor barrier. I don't mean to confuse you , but there are reasons for it. You can go to this is a Dept. of Energy brief on vapor barriers. I would also recommend you check with you local building inspection dept. on codes concerning vapor barriers in your area.

Moisture permeates all materials, some more than others. It does it through a machanism known as diffusion. If you read the brief it explains it. Another fact you have to consider is fiberglass insulation has a very low absorption rate to moisture. Because of this, it is unwise to install FG insulation without a vapor barrier.

In my opinion all you have to do is make sure there are no rips in the silver paper and tape over them if there are. Then install the sheet rock. If something was applied to the exterior of the wall that qualifies as a vapor barrier because of the weather patterns in your area, I would still recommend the aforementioned, provided that the silver paper has a 5 times greater perm rating than the exterior application. On the brief read the section on "Perms" it supports my recommendation.
Old 07-02-02, 09:13 AM
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Thanks for the info. I also asked my local building inspector. He said that I could just use visqueen or put PVA on the drywall. I was going to use PVA to seal the drywall anyway....... No clue what visqueen is. Maybe that is the correct name for the silver paper.

Well at least I can take one bundle of insulation back.

Thanks again
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