First off, GBA is a fabulous resource for us, as we plan to build our “final home” in Asheville, NC. Climate zone 4. Our home will be a 26’ x 44’ ranch with a partially exposed, walk out full basement. Standing seam metal roof, scissor trusses, Zip system wall and roof sheathing, stucco exterior, 3’ eaves and gable ends. We will do a LOT of air sealing, greater than required insulation and high quality windows. The mechanicals and ERV will be in the basement (not in the attic). We will have a simple long gable roof with a 12/12 pitch outside, and either a 6/12 or 8/12 inside ceiling pitch over the living area (we’re still working through the interior aesthetics to determine the ceiling pitch). One end of the house will contain the MBR and bath, which will have a flat ceiling at 9’ height and an attic scuttle hole in the MBR closet. Attic insulation is where we need advice.

• Based on all the articles and Q&A that we’ve read on GBA, it would be less expensive to have a vented attic, and to insulate the floor of the attic with a thick blanket of blow in insulation. Our concern is that the blow in insulation will shift over time given the 6/12 or 8/12 pitch over the living area.
• As an alternative, we could use an unvented roof assembly, and use 3” of closed cell foam on the bottom of the roof deck, plus air-permeable insulation under the foam. Installing the air-permeable insulation could be tedious (and expensive) with the 12/12 pitch and scissor trusses.

Can you provide us a recommendation for insulating the attic?