The garage has 16" on-center studs and rafters. The garage doors have an insulation value of R-12.5. For these reasons, and for price, I chose R-13 insulation for the building. With Tyvek wrap, new windows and doors, it should be a tight, efficient building.
December 28. Most of the insulation will be installed after the electric is finished and inspected, but I want to insulate the middle section of the roof as soon as possible so I can start storing things upstairs. I stapled rigid foam spacers between the joists to allow an airway from soffit to ridge vent. Here are the first ones reaching down to the soffit space:
The insulation is cheapest in 32' rolls. This is perfect for the 16'-long rafter spaces. Unroll, cut in half, staple in place. Easy but not fun. I wear a mask, cap, gloves, overclothes so I don't bring fiberglass into the house:
December 29. Half way done the middle section:
Outside, looking up into the soffit space between the wall and gutter. The rigid foam lets air get to the ridge, the fiberglass stops air from getting into the building:
December 30. Lots of airways:
And insulation. 20 rafter spaces done:
I will do the rest after the electric is inspected. I can hardly wait to do the rafter spaces over the garage bay...
May 25, 2008. Code says I have to cover the paper-faced insulation because it's flammable. OK. I decided to use durable OSB: