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Attic question

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05-09-01, 09:06 PM   #1  
Hi. Around 1980 we added to our bungelow house an addition.
The contractor extended the existing roof to accomodate the new second story. When in the attic of the new addition you can look down and see the old roof, which was left in place. My question is should I put up a plastic sheeting so air does not feed up into the new attic. I had ice dams this last winter, so going to add insulation and plastic venting to help keep the attic colder. The existing insulation, I now find is only R=5.5. I am also wondering if I could use the Miraflex (Corning) R-25 insulation over the old stuff, or would that not be sufficient for the Detroit, Michigan area. Any tips that come to mind would be appreciated also. Thanks Big D

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05-10-01, 09:19 AM   #2  
Any insulation is always better than none at all. More usually helps too.

I would use a material like Tyvek rather than plastic. It will outlast plastic by far. Tyvek and other house wraps are designed to minimize air infiltration.

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05-11-01, 03:08 PM   #3  
I believe if you can still see the old roof under your new roof this would still be considered attic space, so in my opinion there would be no benefit to block air flow..

Curious how you only have a 5.5 R-value in your new attic space.. anyhow I would suggest you call a reliable insulation contractor in your area to give you a free estimate to see what they would do...then you can decide if you want to do the work yourself...

Minimum R value of 30 in ceiling areas is a state code on new builds.. I would reccommend with increasing enery costs to go to and R-38

Miroflex I have found sounds good, but in some cases is difficult to work with (ie cutting - filling voids correctly)

If you buy cellulose from some of the local bulding supply company's they will loan you a blower for free!!

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