The installation can either include ventilation under the roof deck or have no ventilation.
Open cell or radiant for roof.
Open cell spray foam.
R20 open cell foam is fine under roof decks but would not meet the r30 code minimums unless you also had r10 of rigid foam above the roof deck.
Open cell spray foam is made of open cells that are softer and flexible with the physical structure similar to a sponge shape.
Material costs and going with diy the open cell costs about 600 to cover 1 000 sq.
Contractors tend to stop at r20 since it s the thickest layer than can be installed safely and well in a single.
For professional installation plan to pay 2 000 or more.
Using a cool roof material on the exterior is more effective but still not sufficient.
Closed cell foam while also useful in residential construction insulation is used in a variety of commercial industrial and residential applications because of the excellent strength and insulating properties described here.
You can insulate your sloped ceiling with either open cell or closed cell spray foam.
Radiant barrier paint is a scam.
Applications that typically use open cell spray foam include residential construction insulation under roof trusses for conditioned attics and as a spray foam sound insulation in media rooms etc.
No paint exists that meets the technical definition of a radiant barrier.
Ft while closed cell comes in at 1 200.
The final two options are more or less meant to be used in conjunction with one of the above options.