Foam board Insulation. Photo: Getty Images. Spray Foam. Pros: Once sprayed, polyurethane foam sets, expands, and hardens. It’s admirably airtight—often negating the need for additional sealing ...

Q. My house has cathedral ceilings with 2-by-12-inch rafters to which the builder nailed 2-inch-high sleepers, bringing the effective depth for insulation to 13 5 / 8 inches. I had wanted to use ...

Polyiso is a closed-cell, rigid foam board insulation that typically comes in 1, 2, and 4 inch thickness. THERMAX™ and Dow “blue board” are the two most common types of polyiso insulation.