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jvetter713 09-22-2012 06:18 AM

Advice insulating a finished attic wall
I am in the process of finishing my attic and need some help regarding the insulating of one of the walls.

I live in New Hampshire.

Here is a picture of the attic before I started:

I drew a black line to indicate the wall (it extends the entire length of the attic).
My original design was to build the wall like so in order from interior to exterior:

Sheet Rock --> 3.5" Stone Wool Batts --> 1" XPS Foam Board --> Sheetrock as a fire barrier if required because of the furnace.

My question is for the vapor barrier. Do I need one? If I put plastic in front of the batts wouldnt I get in trouble trapping the moisture?

What if I reversed the materials and did:
Sheetrock --> XPS Foam Board --> Studs -> Batt insulation
Sheetrock --> Vapor Barrier --> XPS Foam Board --> Studs -> Batt insulation.

Wouldnt having the batt insulation exposed on the exterior side not be effective because it is not contained in an air tight cavity?

(The attic is vented with soffit vents by the way)

Im confused!

hammerlane 09-22-2012 08:16 AM

2 Attachment(s)
I used an xtra layer of batt and spray foam on wall

jvetter713 09-22-2012 10:56 AM

Not quite what i was looking for though...
Thanks for the reply and nice job!

I'm not looking for advice on insulating above the ceiling though....I'm referring to the insulation within the specified wall.


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