Providing an air space above the sheathing of a roof deck offers thermal benefits for stone-coated or standing seam metal roofs that yield energy savings in the summer and winter, while also helping to remove unwanted moisture. The natural ventilation abpve the sheathing improves the durability of the underlying structure of the roof. Metal roofs are sometimes offset mounted from the roof deck using a double-batten (counter-batten) construction. The design provides an air space between the exterior face of the roof sheathing and the underside of the roof cover so that a clear, albeit complex, air pathway exists beneath the roof cover. Solar irradiance absorbed at the roof's surface is conducted through the metal roof and heats the air space. The warmer and therefore more buoyant air moves up the inclined air passage. The ventilation scheme helps remove unwanted heat but it also removes unwanted moisture from the roof deck, thereby improving the roof's thermal performance as well as its durability. The thermally induced airflow occurring in this air space is termed above-sheathing ventilation (ASV).
展开▼
