Roof coatings can add 25 years to the service life of a roof and reduce the amount of discarded roofing materials that end up in landfills. The infrared image on the right shows 175 °F (79 °C) on the uncoated (black) section of the modified bitumen roof. The coated (white) section is 79 °F (26 °C). Field studies have shown that cool roof coatings can lower rooftop temperatures and reduce air conditioning bills.
Spray foam’s thermal performance and advanced air and moisture control can be optimized by combining it with other insulation products like fiberglass batts or rolls, maximizing budget and meeting energy efficiency goals. Combining insulation products creates a custom solution by leveraging the functions of multiple materials to find the best mix for the project. 
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.

Also, I'm wondering... Is this website is being regularly updated? A local installer (in Oct, 2010) in MA quoted over twice the price you list here. "Open cell alone ~$1.35 per sq ft for R-13. Or a 'hybrid method' using 2inch closed cell for R-13 followed by 1.5inch open cell for R-6. Hybrid is $2.85 per sq foot for R-19 rating". Maybe installers are charging higher prices to profit from those trying to meet government energy rebate by Dec 31?
Another thing we love about the Liquid Roof is its ability of not being damaged by freezing and other extreme temperatures. You will also appreciate its ability of staying flexible for a longer period of time. Did you know that it could also contract and expand as you roof moves? That is one of the things to look for when shopping around for this kind of product we found in the Liquid Roof.
The product is an acrylic coating, which is packed conveniently for ease of use. As it is also in one-gallon size, you can rely on its supreme area coverage reaching up to 125 square feet. The Dicor rubber roof coating is also very easy to apply. When shopping around for a roof coating, we believe it pays off to find an easy to apply product for fast results. It is one of the best qualities of the RV roof coating that makes it a top pick in the category.

Roof Coating