An insulating board in which the capacity to absorb the moisture exemplified by wood fiber based board, cellulose fiber based board and perlite based board is coupled with the high permeability of fiber glass insulation to provide a board having a balance between the capacity to hold moisture and sufficient permeance to allow the board to give up the moisture as the board is passed through a cycle of absorption and desorption, whether it be on a daily or seasonable cycle is provided with an air retarder sheet laminated thereto, which while it provides an air retarder and a water shield has a high permeance so as to allow water vapor to pass through.