Polyisocyanurate Foil-Faced Boards are very enery efficent building materials. Usually its used in foundations, exterior walls and other places what will need good moisture resistand values and also good thermal insulating. Its a little bit expensive than unfaced polyisocyanurate boards, but you do not have to finish the surface.

Usualli it comes with special measures like ½ inch thik 4x8 sheets. Top surface is aluminum foil in both sides and top of aluminum there are placed some kind of fiber or laminate facing.

Its very easy to handle and all contractors and builders love it.