Polyurethane Foam Roofing

Sprayed polyurethane foam (SPF), a type of plastic based foam for roofing applications, is installed as a liquid and expands in about 3 seconds to over 1,000 times its original size. SPF foam forms a walk-able surface in about 60 seconds. SPF is environmentally safe, and uses a patented blowing agent made from water instead of ozone. It is completely inert and is in fact the primary insulator used in both residential and commercial refrigeration units (for example, the refrigerator in your home probably uses polyurethane foam).

Below: Sprayed Polyurethane foam is very popular for large commercial applications, such as the one pictured below. Foam roofing materials last 40 or more years and require minimal maintenance. Even if the elastomeric coating is penetrated, a foam roof continues to waterproof and protect due to millions of tiny closed cells. Large buildings like the one below also benefit from the excellent insulation foam provides. Due to several factors, just a single inch of SPF foam is more effective than four inches of fiberglass! The roof below most likely has one to two inches of foam (12 to 16 in R-Value).


SPF foam for roofing applications is inherently water resistant due to its closed cells. Just one inch of SPF foam has about 1 million tiny closed cells. SPF forms to any structure it is sprayed on, and creates a seamless monolithic barrier to the elements.

For any application, including roofing, closed cell polyurethane foam is formulated by manufacturers to get the best combination of durability, flexibility, and thermal resistance. The closed foam used for roofing is durable, high density, and watertight. In contrast, foam used in things such as mattresses or pillows is very low density, open cell, and water absorbent. SPF foam roofing is a type of polyurethane (PU) plastic.

Below: A sample of foam is pictured below. The foam, composed of millions of tiny closed cells is sprayed directly on to a substrate. There are two layers of elastomeric acrylic coating on top of the foam. The grey base coat will help a professional know when UV light has worn through the white, reflective top coat. Although 'foam' might imply a soft weak material, the formulation for a foam roof is very different and feels similar to walking on a concrete sidewalk.

What is Polyurethane (PU)?

Polyurethane (PU), a form of plastic, is a polymer formed by a chain of organic units joined by urethane (carbamate) bonds. Polyurethane polymers are formed by reacting two monomers with a catalyst. Here are a few common examples of various PU foam applications: insulation, seating, pillows, bedding, automotive suspension bushings, electrical potting compounds, high performance adhesives and sealants, seals, gaskets, carpet underlay, hard plastic parts, and (of course) roofing materials. The density, composition, and other qualities of PU in each application varies greatly depending on the planned purpose.

Below: A polyurethane foam three dimensional cut-away view. See how the foam contours with the edge of the roof, vent, and skylight. Closed cell foam is the best insulation on the market, and the type formulated for roofing is actually extremely durable, lasting forty or more years.

History of Foam Roofing

The foundation work that led to modern day uses of polymers occurred in 1937 at I.G. Farben Laboratories in Germany. There a team led by Otto Bayer discovered that the polyaddition principle to produce polyurethanes from liquid diisocyanates and liquid polyether or polyester diols had some untapped potential. The new monomer combination also circumvented existing patents obtained by Wallace Carothers on polyesters. Early testing focused on the production of flexible foams and fibres, and around 1952 polyisocyanates became commercially available as rigid foams, gum rubber, and elastomers and Linear fibres. During the 1960s automotive manufacturers began using PU based interior safety components such as instrument panels and dashboards. In 1983, the first PU plastic based automotive body body was introduced (the Pontiac Fiero). During the 1980s automotive manufacterrs also began using water-blown microcellular foam gaskets and seals (e.g. for air filters). Some of the early manufactures of PU products included DuPont, BASF, Dow Chemical, and Mobay Corporation.

It's surprising how often people have misconceptions about polyurethane spray foam considering the technology has been available for over 50 years now. As the public becomes more aware of the importance of insulation, and the need for a superior flat roofing material, this green, environmentally friendly product will continue to grow in popularity.

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Thanks for a good post, I personally found this explanation of spf and foam roofing very helpful. i only wonder why foam roofing is not more widely used or better known.