Sprayed Polyurethane Foam (SPF)

SPF adheres to just about everything so it can be installed over concrete, wood, steel, and most existing roof systems (EXCEPT APP!) which saves on the expense of roof removal and landfill fees. SPF mechanics can spray apply a tapered roof system with the foam which eliminates the need for costly tapered insulation systems. The cants and vertical wall terminations are also spray applied making them an integral part of the roof system and minimizing additional component costs.

INSTALLATION
The "A" and "B" components of SPF are pumped out of separate 55 gallon drums, are mixed at the spray gun, and are applied in what are known as "passes". A pass is a single application of foam and can vary in thickness from 1/2 inch to 1 inch or so. Therefore, SPF roofs that are several inches thick are applied in multiple passes.

SPF must have a protective elastomeric coating installed over it because it's very susceptible to UV and mechanical damage. Elastomeric means the coating must be able to stretch with the foam and return to its original shape. Coatings are spray applied and can be acrylic, silicone, butyl rubber, and different urethanes. All have different physical characteristics and varying costs. Coatings are usually installed in three stages: a base coat, a mid-coat, and a final coat. Granules can be embedded into the mid and top coat or only the top coat for added protection against UV and mechanical damage and to increase the system's fire resistance.

DURABILITY
When most people hear of a "foam" roof, they automatically think of the type of soft foam similar to that used for seat cushions and are concerned that they won't be able to walk on it without causing problems or damaging the roof. Foam roofs are very durable and can handle foot and construction traffic as well as other roofs. They are still susceptible to damage from dropped tools just as any other roof but the damage is more easily seen and can most often be repaired with some simple polyurethane caulking.

DENSITY & R-VALUE
Density of SPF is important when it comes to strength and Thermal Resistance. Obviously, higher density means increased strength and higher R-value. Most SPF roofs have densities ranging from about 2.5 pounds per cubic foot to 3 pounds per cubic foot. Three pound density foam has a compressive strength of about 50 psi and an R-value of 7.14 installed and 6.86 aged (these numbers may vary slightly depending on the foam manufacturer). Here's an example of how well a good SPF roof insulates. A school district in southern California had recently installed some new, one-room relocatable classroom buildings. During the late spring and early fall, these classrooms were using their air conditioners an average of 50 minutes every hour. The school district installed foam roofs on some of these classrooms in order to see if it would provide an energy savings. The roofs consisted of three pound density foam, 1.5 inches thick with an acrylic coating system. The air conditioner usage was cut down to fifteen minutes every hour. That's a fifty-eight percent savings on energy costs.

Does this mean an SPF roof pay for itself? Absolutely! Texas A&M studies indicate that an SPF roof in Texas and other southern climates can pay for itself in approximately four and a half years.

LIFESPAN
If the coating for an SPF roof is properly maintained, then an SPF roof can last a very long time. Every ten or fifteen years, depending on the type and amount of coating installed, the roof will need to be cleaned, primed, and recoated. If this is done, then a quality SPF roof could last 50 years or longer.

COST
As with all other roof systems, cost depends on several factors. Some of which include building accessibility, complexity of project, foam thickness, foam coating system, and geographical location. Costs may start at about $2.50 per square foot for a cheap system and go up from there.

SOME THINGS YOU SHOULD KNOW
Foam roofing requires a lot quality control by the foam mechanics who do the work. If the gun gets dirty or a hose gets clogged or any one of a hundred things goes wrong, the mechanics must be able to recognize the problem and be willing to shut down operations until the problems can be taken care of. This isn't an easy thing to do because shutting down an operation costs a lot of time and money and may cost the mechanic a bonus for the job. Pride in workmanship is an extremely important factor in a quality foam roof.

A rating system for foam contractors has been developed by Arizona State University's Performance Based Studies Research Group (PBSRG) headed by Dr. Dean Kashawagi at the Del E. Webb School of Construction. While there are surely many good foam contractors who haven't been rated by this group, RoofHelp recommends visiting the web site of PBSRG when looking for a high quality foam roofing contractor.
http://www.eas.asu.edu/pbsrg