How does Foam Insulation control moisture movement and condensation?

Most damaging moisture within a building envelope cavity is the result of warm moist inside air being exchanged with the cold dry air inside an insulation cavity. As the moisture in the air condenses, it forms dew within the insulation. Because foam insulation is an air seal, this moisture movement and condensation does not occur. It is ideal for use in climates where buildings are both heated and air conditioned because the situation is reversed in summer with moisture forming on the back of the interior vapor retarder.