Closed cell spray foams are an excellent choice for duct sealing, creating air barriers and air sealing. Because it is made of closed cell technology, it is much more dense type of material than open cell chemistry. It has a smaller, more compact cell structure. It is a very good air barrier sealant as well as a water vapor barrier.
Air barriers block random air movement through building cavities. As a result, they help prevent air leakage into and out of your home, which can account for 30% or more of a home's heating and cooling costs. Although they stop most air movement, air barriers are not necessarily vapor barriers. The placement of air and vapor barriers in a structure is climate-dependent, and it’s wise to work with building professionals familiar with energy-efficient construction in your area.