Abstract: A structure can be prepared comprising a substrate, such as a wall, ceiling or floor, and, as a non-covered layer applied thereon, a spray polyurethane foam. The foam formulation used to prepare the spray polyurethane foam includes a polyol component having a functionality equal to or greater than 2.1, an isocyanate component having a functionality equal to or greater than 2.7, an aromatic bromine-containing flame retardant agent, a phosphorus-containing flame retardant agent and a blowing agent. The structure containing the spray polyurethane foam is capable of passing the International Code Council Evaluation Service's Acceptance Criteria 377 Appendix X test without covering the spray polyurethane foam or coating the spray polyurethane foam with an intumescing coating, and therefore can be particularly useful in attics, crawl spaces, and other areas in which the foam would be exposed.