An insulation board (10) insulation board comprising a foam core (11) selected from the group consisting of polyisocyanurate and polyurethane materials and mixtures thereof; the board being devoid of facers. A method of covering roofs comprises applying insulation boards to a roof deck, the insulation boards comprising a foam core selected from the group consisting of polyisocyanurate and polyurethane materials and mixtures thereof, the boards being devoid of facers; and, applying a weather protective layer over the insulation boards. A continuous method of making a facerless insulation board comprising the steps of feeding a first sheet (24) of temporary facer material into a laminator (25); depositing a foamable polymer liquid (40) onto the first sheet; feeding a second sheet (23) of temporary facer material into the laminator above the foamable polymer liquid; allowing the polymer liquid to rise between the first and second sheets forming polymer foam (44) of a pre-determined thickness; curing the polymer foam under heat (45) to create the insulation board; removing the first and second sheets from the board prior to final curing and cooling; and cutting the board to desired lengths.