Profile: Mercury Building Products Ltd. specializes in supplying quality and performance materials required in pitched & flat roofs. We supply vapor permeable roof underlays and insulated cavity closures. VapR-free is a multi-layer laminate film composite made of polyolefin materials. Our vapor permeable pitched roof underlays are highly water resistant and breathable, and also eliminate the need for roof space ventilation. Classic closures are manufactured from closed cell extruded polystyrene insulation and u-PVC extrusion.