Spray Polyurethane foam Spray polyurethane foam provides the best R-value of any roofing solution. R-value is the ability of an insulating material to resist heat flow. Thus, it keeps the cool or heat from escaping the structure.  It is sprayed as a monolithic layer over an existing system. It covers all seams and holes from a previous roofing system. Closed-cell spray foam is impenetrable by water. Silicone Restoration Membrane Some building owners transition from a rubber roof and choose Silicone Restoration Membrane due to the gray/white color of the coating. Using white silicone can decrease the energy use of your building. Silicon restoration membrane is sprayed or rolled over an existing roofing system. Like SPF, it also covers all seams and holes from a previous system and is considered waterproof.