Roof Insulation Approach
I’m building a single story addition and researching roofing insulation options. I’m considering an option where I use 11.5″ ijoist rafters with a luan panel nailed to the bottom of the top ijoist flange in each rafter bay creating a vent channel from soffit to ridge. For insulation – total to be R49 – I would install 2″ foil-faced polyiso to the underside of the ijoists and foil tape it to create my air barrier. Finally, I would dense-pack cellulose the rafter bays through holes in the polyiso. So I believe I have my air barrier on all sides of the cellulose. My intent is to allow the roof to dry to the outside – through the luan panels – for any moisture that may accumulate in the cellulose. Does this approach sound good? Any issues?
GBA Detail Library
A collection of one thousand construction details organized by climate and house part