Spray foam insulation is a type of building insulation made by mixing two chemicals (usually isocyanate and polyol resin) that react and expand into a foam when sprayed. The foam fills gaps, cracks, and cavities in walls, ceilings, roofs, and floors-then hardens into an insulating and air-sealing layer. There are two main types: Open-cell spray foam - lighter, softer, good for interior walls and sound reduction Closed-cell spray foam - denser, stronger, higher insulation value, often used for exterior walls, roofs, and basements Because it seals air leaks, it helps: Maintain stable temperatures Reduce drafts Reduce allergens and outdoor pollutants entering the home Typical Places Spray Foam Is Used Attics / roof decks Exterior walls Basements and rim joists Crawl spaces spray foam insulation batt insulation dense pack insulation attic insulation insulation repair residential insulation commercial insulation remodeling projects energy efficiency