I'm remodeling the upper floor of a ~100 year-old house near Portland, OR. It's down to beams: all the drywall (and plaster) has been removed, along with all the old insulation. I'm about to replace the roof which will require a complete tear-off and new decking (or is it called sheathing?)
The roof is framed with old-style 2x4s (actually 2" x 4"). The roof decking will be installed on the top, and sheet rock to the bottom, so there isn't much room to add insulation and ventilation.
There is, actually, a small attic space about three feet under the peak of the roof. But most of the ceiling is shared with the roof. The pitch is quite steep.
One contractor told me I could fill the entire 4" depth with sprayed-on liquid foam insulation to maximize the R-value. He said it was allowed by code because this foam couldn't absorb water.
A second contractor said I should use the traditional soffit/ridge venting even though it would reduce my insulation by half.
I'd prefer the better insulation; it gets hot up there in the summer.
Are both of these viable? Are they both allowed? I need to tell my roofer if he should install soffit vents...