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Eave Insulation

Eave Insulation

New postby mtCDCcb on Mon Jun 10, 2013 11:07 am

I am building a new entry to my home, what we here call a "mud room". It is 7 1/2' by 10' with its own roof as it is an attachment to the existing home. The eaves extend 8' and my question is do I need to insulate the eaves and why or why not? Additional info: We live in climate zone 7 and are under the 2009 IRC (IECC). Thanks for your help.
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Re: Eave Insulation

New postby Jerry Peck - Codeman on Thu Jun 13, 2013 9:44 pm

Sorry I missed seeing your question until now, not sure how I missed it ... may have something to do with the 12-13 hour days I've been working ...

The energy code is concerned about any heated and cooled (conditioned) area, and the area past the exterior walls is outside the thermal envelope of the building. The thermal envelope of the building would be the area defined by the inside surface of the insulation, typically that would be up the exterior walls, across the attic floor, then down the other exterior walls (with spray foam insulation on the underside of the roof, the thermal envelope would be up the exterior walls, up and back down the roof slope, and down the other exterior walls, the attic area between the insulation on the roof deck and the ceiling is still considered 'conditioned space' but you do not need to 'condition' it as it assimilates to within a couple of degrees of the interior of the house through air movement through the ceiling).

With the eaves being outside the thermal envelope, no, you would not need to insulate them, however, if your area is subject to ice daming, then it may be beneficial to insulate that area, along with some type of 'water and ice' shield peel-and-stick material extending from the eaves up 3', 6', or maybe even 12' - why not cover the entire roof with a peel-and-stick underlayment as that would give much improved leak resistance over the old roofing felt underlayment.
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