Check with the coating manufacturer who may be able to suggest applicators who have used their products and have familiarity with the application. Another option would be to interview contractors and ask specific questions about their proven ability to install roof coatings. Contractors affiliated with the National Roofing Contractors Association (NRCA) or local roofing contractor trade associations typically are more knowledgeable. Consult those groups’ websites for contractors.
Although spray polyurethane foam has many advantages over other types of insulation, spray foam installation isn’t foolproof. Some builders have reported problems with sloppy foam insulation. For example, some installers have been known to begin spraying before the chemical components are up to temperature, which can affect component mixing and foam performance. When components are poorly mixed, or mixed in the wrong ratio or at the wrong temperature, cured foam has been known to shrink away from rafters or studs, leaving cracks. Some installers rush through their spraying, resulting in voids.
We are turning our roof into an unvented roof assembly by raising the roof and blowing in SPF. We are planning to leave the existing vapor barrier down but remove the fiberglass batting and then adding 6" of SPF in all the cavities, to completely seal and insulate the house. Should we have any concerns about doing it "upside down" and not spraying the foam directly to the underside/sheathing of the roof?
The process by which heat energy in the form of light (usually IR unless the substrate is hot enough to glow in the visible range) is emitted more strongly by warm surfaces and absorbed by other materials especially those of low IR reflectivity (think matte black finish). Radiant heat transfer does not require a medium. Foam insulation materials, such as spray foam insulation, are opaque to thermal radiation, like most solid materials.
The drawback to spray foam insulation is it's been known to cause certain health issues such irritation of the eye and the gastrointestinal and respiratory tracts. Direct contact can cause inflammation to the skin, and some individuals have been known to break out in a rash on the arms, chest and neck area. Spray foam insulation has also been linked to a few cases of hypersensitivity pneumonitis. This condition can cause: