Weather barrier mastics are also called breather mastics. Breather mastics have a perm rating over 10; DP 5050 and DP 5060 have a rating of 20. Breather mastics allow built up vapor pressure to pass through the mastic, thus allowing it to breath. Breathing helps prevent corrosion. Vapor barrier mastics like DP 3040 may be used outdoors to protect insulation, but corrosion could become a problem. The general rule of thumb is that weather barriers should be used outside the building envelope and vapor barriers should be used inside the building envelope.
- May be used for coating fiberglass, polystyrene board, closed cell polyethylene and polyurethane foams in mechanical and industrial thermal insulation applications.
- May be used for bonding and coating of fiberglass mesh, canvas or other lagging fabrics over most types of thermal insulation.