Icing on the . . . Cake??

     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