Abstract: A composite panel product is provided which is intended to be applied as a multitude in building block manner to produce a thermally insulative covering assembly upon an existing wall of a building. The panel product is made of a rigid panel of closed cell polymer foam of rectangular perimeter having front and rear surfaces. The front surface has parallel upraised ridges. A stiff fabric is attached to the ridges, spanning the entire front surface and extending beyond two contiguous edges of the perimeter as spanning borders of uniform width. The spanning borders partially overlap and interlock adjacent panel products. A cementitious layer is applied to the fabric side of the assembly of panel product.