R-49 attic insulation is recommended for this climate, and I spec R-60 for most attic floors because cellulose is cheap.  Yet my own unconditioned attic has an effective R-value of only about 20.  There is a typically settled loose-fill cellulose job from the early 80s under the floorboards.  I decided to relocate the thermal boundary to the top of the loose tongue-and-groove attic floorboards and to the perimeter of the attic floor plane, creating in effect an inverted, insulated box over the living space. I added 2” of extruded polystyrene board and covered it with OSB.  There is no condensing surface inside my inverted box.

 

      I paid special attention to the exterior top plates and (perhaps most importantly) I personally attended to or oversaw every detail.  This led me back to the inescapable truth is that attention to workmanship is the key to building performance

 

 

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Comment by Joseph J. Ilacqua on February 23, 2011 at 9:12am
Geez, I wonder who insulated the walls on that house, Chris is taking credit for the attic, my memory isn't quite as sharp as it used to be, i can't remember

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