Insulated built up roof and insulation therefor

Claim 1

A COMPOSITE ROOF STRUCTURE COMPRISING A ROOF DECK, A LAYER OF INSULATION OF SUBSTANTIALLY UNIFORM THICKNESS COVERING THE DECK, THE INSULATION A PLURALITY OF RELATIVELY LARGE, SUBSTANTIALLY RECTANGULAR UNITS IN EDGE ABUTTING RELATION, EACH UNIT CONSISTING OF A RECTANGULAR CORE OF RIGID URETHANE FOAM OF UNIFORM COMPOSITION THROUGHOUT THE CORE, CONTAINING AT LEAST 50% CLOSED CELLS, HAVING A THICKNESS OF FROM 1/4 INCH TO 8 INCHES, A COMPRESSIVE STRENGHT OF AT LEAST 10 POUNDS PER SQUARE INCH WITH NO MORE THAN 5% DEFORMATION, A DENSITY OF FROM 1.1 TO 4 POUNDS PER CUBIC FOOT, A FLEXURAL STRENGTH OF AT LEAST 20 POUNDS PER SQUARE INCH AND A K VALUE NOT EXCEEDING 0.24 B.T.U. PER HR. PER SQ. FT. PER INCH THICKNESS PER *F., AND A LAYER OF FELT SATURATED WITH A BITUMINOUS WATER-PROOFING MATERIAL AND COACTED WITH A BITUMINOUS WATER-PROOFING COATING MATERIAL FACTORY BONDED TO EACH OF THE OPPOSITE SURFACES OF SAID URETHANE FOAM SO THAT SAID UNITS AS LAID EACH HAVE THE FOAM CORE PROTECTED BY SAID FELT COVERING THE OPPOSITE SIDES THEREOF, AT LEAST ONE OF SAID LAYERS OF FELT HAVING A LAYER OF ANTI-STICK MATERIAL ON THE SIDE OPPOSITE THE URETHANE FOAM CORE, SAID ROOF STRUCTURE HAVING ON SAID LAYER OF INSULATING ALTERNATING LAYERS OF WATERPROOF COATING AND BONDING MATERIAL AND FELT WITH THE TOP COATING LAYER ON THE TOP FELT LAYER HAVING A WEARRESISTANT SURFACE.