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 or radiant for roof.
Material costs and going with diy the open cell costs about 600 to cover 1 000 sq.
For professional installation plan to pay 2 000 or more.
As an example the worst performing osb in climate zone 4 is the osb on a north facing roof insulated with open cell foam over an attic with a duct system that is fairly well sealed 4 duct leakage an attic floor which is fairly leaky 2 0 cfm50 cfa and a house with high indoor moisture production.
Less common of the two types of spray foam open cell is mostly used for residential and commercial insulation.
Contractors tend to stop at r20 since it s the thickest layer than can be installed safely and well in a single.
The installation can either include ventilation under the roof deck or have no ventilation.
Even if it did its effects are small compared to insulation.
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.
Open cell spray foam is made of open cells that are softer and flexible with the physical structure similar to a sponge shape.
Ft while closed cell comes in at 1 200.
Open cell spray foam.
The final two options are more or less meant to be used in conjunction with one of the above options.
No paint exists that meets the technical definition of a radiant barrier.
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.