Solvent-based polyurethane coatings have excellent adhesion and when used as a base coat over asphalt, EPDM, TPO or PVC, it eliminates the need for a primer. The resulting savings on labor and material more than offsets the higher cost of the product. When top coated with silicone, it gives you the best of both worlds. It's also an excellent gutter and RV coating.
Closed-cell (aka two-pound foam) is denser than open-cell at about 2 pounds per cubic foot. Its R-Value is between 6-6.5 per inch. As a result, this kind of foam is much more expensive than its counterpart. The reason closed-cell doesn't need a vapor retarder is because it already has one. It's permeance is 0.8 perm, which means it can handle cold climates without the use of an additional board or drywall. Closed-cell uses hydroflurocarbons (HFCs) as part of its makeup. However, this material has been known to have a high global warming effect. If you want a green insulation solution, this is not the material to use. A way to avoid this and still use closed-cell is by installing it alongside fiberglass batts. https://youtube.com/v/ggLAUsiuI_o?version=3
Closed-cell foam has a higher density and offers a higher R-value per inch. It also adds strength to walls, ceilings and roofs and can contribute to a structure’s overall durability. Additionally, closed-cell foam’s low water vapor permeability offers protection from moisture when installed in places where high humidity—from climate, occupants, or flooding—meets the structure. 
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? https://m.youtube.com/e/ggLAUsiuI_o
Sporadic cases of hypersensitivity pneumonitis (HP) have also been reported in workers exposed to isocyanates. The symptoms may seem like the flu, with fever, muscle aches, and headaches. Other symptoms may include a dry cough, chest tightness, and difficult breathing. Individuals with chronic HP often experience progressively more difficult breathing, fatigue, and weight loss. Individuals with acute HP typically develop symptoms 4–6 hours after exposure.[4]
Some states, municipalities and utilities have programs. Check with your coatings manufacturer for further information. As a membership benefit, RCMA provides maintains a database of current information on rebates and tax credits for installing reflective roofs. RCMA’s customized search tool can be used to find the most up-to-date listings of reflective roofing financial incentives available.
FROTH-PAK Foam Sealant is a two-component quick-cure polyurethane FROTH-PAK Foam Sealant is a two-component quick-cure polyurethane foam that fills cavities penetrations cracks and expansion joints. FROTH-PAK foam sealant can also be used as a sealant and void fill in many roofing applications. FROTH-PAK is chemically cured foam which significantly reduces curing time. FROTH-PAK dispenses expands and becomes tack ...  More + Product Details Close
What more is that we also think it is one of the most durable among liquid roof coatings on the market. It can last for several years, working continuously in protecting your roof from outside elements, such as dust, leaves, twigs and debris that would otherwise damage your roof. When it happens, your roof might have leaks and cause discomfort inside your RV.

Spray foam insulation systems effectively seal walls, roofs, corners and other surfaces, creating a more comfortable household because it provides a barrier against drafts and associated pollen and dust. Long-term, properly installed spray foam won’t change its form or shape, meaning it will deliver the same benefits that it did years—or even decades—after being installed, while other insulation materials may settle and create future gaps in the insulation. 
R-value is the term given to thermal resistance to heat flow. The higher the R-value of an insulation product, the more effective the insulation properties. Spray polyurethane foam comes in a range of densities and cel structure. Low density foams are referred to as Open Cel SPF while higher density foams are referred to as Closed Cel foam. 1.8-2 pound polyurethane foam has the highest R-value of readily available spray foam insulation used in homes and buildings.[4]

Roof Spray Foam Insulation

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