Spray Polyurethane Foam (SPF) Roofing

Spray polyurethane foam (SPF) is a site-applied foam insulation material that comes in a range of types and densities. The CP considers a rigid, closed cell spray foam of about 3 pounds per cubic foot density that can be used for exterior flat or low-slope roofing. These products can be used in new construction or re-roofing applications for commercial, residential, or industrial construction and create a seemless roofing material. The insulation can be installed directly to the roof deck over a number of roof substrates including metal, plywood, concrete, built up roofing, modified bitumen, or single-ply roofing membranes. A primer may be required in some cases. Primers may be acrylic, epoxy, or alkyd materials. SPF application requires that both air and substrate temperatures are between 50°F - 120°F, with a relative humidity less than 85%. It is should also be noted that depending on temperature, particular grades of SPF with different reactivites are required. Furthermore, within 24 hours of installation UV coatings must be applied in order to prevent degradation of the SPF. Coatings can be silicone, acrylic, polyurethane, or butyl rubber. Granules can also optionally be applied for increased durability. Accessories used with spray foam roofing are outside of the scope of this CP and may add additional hazards. 

SPF is a two-part polyurethane based foam comprised of a isocyanate part (the A side) and a polyol part (the B side) that are combined and reacted on site as applied. The B side of SPF also contains blowing agents, flame retardants, catalysts, and surfactants. Closed cell foams, such as those used for roofing applications, typically use fluorocarbon blowing agents, including hydrofluorocarbons (HFCs) with a high global warming potential (GWP), or hydroluoroolefins (HFOs) which are newer low global warming potential alternatives. While HFOs do not themselves have high GWP, they do use high GWP and/or ozone depleting substances in the manufacturing process. U.S. EPA regulations that would have prohibited the use of HFCs in SPF insulation by 2020 were partially overturned in Federal court rulings, so manufacturers already using HFCs are allowed to continue using them. Several U.S. states have moved forward with their own bans on HFCs in SPF, many of which have gone into effect(Theodoridi, 2020). Most spray foam insulation manufacturers continue to offer their HFC versions of SPF, even as many have introduced an HFO version. Because HFC versions are allowed in most states in the US and most manufacturers offer both types, this CP covers spray foam roofing made with an HFC blowing agent. Formulations that instead use HFOs appear to be similiar. See the All Contents tab for contents found in both HFC and HFO versions. 

Since SPF products are reacted and applied on site, special care must be taken to avoid exposure to the isocyanates, amines, flame retardants, etc. for workers and others who may be present during the application process. Many SPF applicators undergo training and professional certification. Even for exterior applications like roofing, personal protective equipement typically includes full body protection in the form of disposable coveralls, chemical-resistant gloves, and eye and face protection as well as supplied air respirators or NIOSH-approved air purifying respirators. Care must be taken to prevent mists or vapors from entering the building air intake for the ventilation system (typically done by turning off the building ventilation system and applying plastic sheeting securely over the air intake) and also to protect surroundings from overspray.