Spray Foam Insulation FAQ Overview

Spray foam air-seals as well as insulates — expanding to fill cracks and gaps that fiberglass simply lets air pass through (which is why you'll often see dust rings around the gaps in old batts, the fiberglass acting like a filter rather than a seal). It also offers the highest R-value per inch of commercially available insulation, and pre-pressurized, point-and-shoot kits make it easy to apply without special equipment.

A standard kit includes two pre-pressurized tanks — one holding the A-component and one holding the B-component of the two-part foam system — along with two hoses, a plastic foam gun, eight nozzle tips, a small packet of petroleum jelly, and a wrench.

Closed-cell foam has a denser, rigid structure with tightly packed cells, giving it a higher R-value per inch — roughly R-6 to R-7 — along with built-in moisture resistance. Open-cell foam is softer and less dense, with an R-value closer to R-4.4 per inch, and it's vapor-permeable rather than a moisture barrier. Closed-cell tends to suit exterior-facing and moisture-prone areas; open-cell is often chosen for exterior walls in some hot/humid climates, interior cavities and sound dampening.

Slow-rise foam has a longer tack-free/expansion time (60–90 seconds), which reduces its expansion pressure. Slow rise is typically used to spray into fully enclosed cavities where the lower expansion pressure reduces risk of bulging the walls of the cavity that is being filled. With extra precautions, certain contractors have used it successfully to fill existing sheet rock walls without tearing down the sheet rock. Other applications include marine buoys, pontoons on boats, and concrete block walls. Quick-cure (fast-rise) foam sets in 30–60 seconds and is only used when you can physically see the surface you are spraying onto. It is the go-to for walls, rim joists, crawl spaces, and metal buildings.

R-value depends on the specific kit and cured thickness, since closed-cell and open-cell formulations perform differently per inch of thickness. R-values range from R4.4 per inch up to R6.7 per inch. Each kit's technical data sheet lists the tested R-value at various thicknesses — check this specification while comparing kits or planning coverage.

Yes. While different kit types carry different ratings and test suites depending on formulation, our kits generally carry Class A fire ratings to meet the highest fire safety standards in their category.

R-value can differ depending on how it's tested — thickness, test method, and whether it's an initial reading straight off the tank or an aged, in-service value all change the number. In general, most closed cell spray foam kits have similar characteristics when it comes to actual R-values for each of the different types of spray foam.