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Any value to ceiling insulation when constructing a conditioned attic?

I'm ready for insulation in my retrofit project, zone 3 in North Carolina. The building has 1 1/2" of poly foam on the exterior 2x6 walls, which will be filled with cellulose. The roof deck has 3" of poly, the underside will have 6" of open cell foam sprayed onto the underside of the roof deck. My question: The insulation contractor has suggested that I may want to add 6" of cellulose blown in at the ceiling level. I can see some value here preventing sound from migrating between rooms (common walls will be insulated for sound as well), but is there any thermal benefit to be gained here?

Thanks

Bill

Asked by Bill Savoie
Posted Fri, 01/25/2013 - 08:37

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2 Answers

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Bill,
You are planning to install a roof assembly insulated to R-44. That's pretty good. However, if you add 6 inches of cellulose at your ceiling level, you'll get an additional R-22 of insulation, which will lower your energy bills somewhat.

Are you planning to use the attic as living space? Or will it be empty? To get any benefit from the 6 inches of cellulose, you have to make sure that there aren't any forced-air registers in the attic.

Answered by Martin Holladay, GBA Advisor
Posted Fri, 01/25/2013 - 10:23

2.
Helpful? 0

Thanks for the response. The attic is just empty space. I'm using mini-splits so that I can control each room individually. Two bedrooms will only be used when we have guests in, so I didn't want a traditional system that is difficult to zone. I am putting in a whole house dehumidification system to control moisture in the two sealed crawlspaces, the basement, and the main house.

Answered by Bill Savoie
Posted Fri, 01/25/2013 - 17:46

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