A type of board composed of some fibrous material, such as wood or other vegetable fiber, sized throughout, and felted or pressed together in such a way as to contain a large quantity of entrapped or dead” air. It is made either by cementing together several thin layers or forming a non-laminated layer of the required thickness. It is used in plain or decorative finishes for interior walls and ceilings in thickness of 0.5 and 1 inch (in some cases up to 3 inches) and also as a water-repellent finish for house sheathing. Desirable properties are low thermal conductivity