Spray Foam Confused
I have an 1,100-sq.-ft. 2-story Cape with two 14 ft. dormers for bedrooms on the 2nd floor. It is 90 years old, currently gutted. I want to insulate it well, but within some equitable reason.
Currently, the house has 1/2-inch rigid foam, R-3.6, on the exterior walls. I want to spray the roof line and enclose the whole envelope.
This is my problem. Three companies have provided estimates now. Two say open-cell foam, 7″-8″ on the roof and 3.75″ on the walls. One company just quoted 7″ open-cell foam on the roof and 2″ closed-cell foam on walls. Estimates vary between $4,500 and $5,500.
Will 2 inches of closed-cell foam perform better than 3.75 inches of open-cell foam?
Last question: has anyone had any experience installing rigid foam within the rafter cavities, like the poor man’s way?