A spray foam hot roof is an unvented insulation system where closed-cell spray foam is applied directly to the underside of the roof deck, sealing the space to create a single thermal envelope. This application prevents air leakage, significantly improves energy efficiency, and can lower utility bills by blocking conditioned air from escaping. By eliminating thermal transfer (sunlight) through a shingled roof the lifetime of the shingles can be increased. While the name "hot roof" refers to the surface temperature being slightly warmer due to the lack of ventilation, the system's primary benefit is creating a conditioned attic space that maintains a more consistent indoor temperature.