Abstract: An insulating structure comprises a board of insulating material having two major surfaces, two side edges and top and bottom edges, and facing sheets on each of the major surfaces, and a generally rectangular closure strip having two equal and integral side portions. One side portion is bonded to one of the facing sheets and extends over said facing sheet from the top edge to the bottom edge and inwardly a short distance from one of the side edges of the board. The other side portion extends outwardly away from the board a short distance from said side edge. A plurality of the insulating structures are positioned in abutting relationship to form an insulating envelope covering a wall or roof of a building.