Spray foam insulation is either open-cell or closed-cell. While both are exceptional, they have different costs, applications, and capabilities. All spray foam insulation is made up of many tiny cells or bubbles. With open-cell foam the cells are open, which gives it a soft feel and a lower density. Open-cell spray foam has a lower insulating value than closed-cell (about R-3.5 per inch). Open-cell foam is ideal for most residential applications in walls, floorspace, and attics. It has exceptional noise reduction and is less expensive than closed-cell. Closed-cell spray foam has closed cells or bubbles that are more tightly packed together and the cells are filled with a gas instead of air as with open-cell foam. Closed-cell foam is stronger (rigid), resists air and water penetration, and is the superior insulator (R-7). Closed cell foam strengthens a structure due to its rigidity.