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U-Value for attic

HappyBetty · 2009-05-12 10:20:11

Hi All, i hope someone can help with this. I have an attic that is unheated with a pitched roof. If i insulate between the rafters with spray foam insulation will i get a better U-Value than inuslatin between the joists at ceiling level. Will the extra layer of air cause the u-value to decrease? Thanks :)

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12-05-2009 11:20am

#1

HappyBetty

Closed Accounts Posts: 5 ✭

Join Date: January 2008

Posts: 1

Hi All,

i hope someone can help with this. I have an attic that is unheated with a pitched roof. If i insulate between the rafters with spray foam insulation will i get a better U-Value than inuslatin between the joists at ceiling level.
Will the extra layer of air cause the u-value to decrease?

Thanks

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#2 12-05-2009 1:43pm
blackbox

Registered Users Posts: 4,361 ✭✭✭

Join Date: November 2007

Posts: 4315

By "between the rafters" I presume you mean put a layer of foam right under the roofing felt.

As attics are normally well ventilated, there will be cold are circulating up there (under your foam), so i believe you would be best to insulate above the ceiling. The only reason not to go this way is if you are planning to convert the attic to a living space.

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