Gravity Ventilators – FGI / FGR, GRSI / GRSR, WIH / WRH and RGU
Gravity roof ventilators shall be constructed of heavygauge aluminum or galvanized steel as specified. Hoods shall be constructed of precision formed, arched panels with interlocking seams. Bases shall be constructed so that the curb cap is 6 inches (152 mm) larger than the throat size. Standard base height shall be 5 inches (127 mm) for most sizes. Optional 12-inch (305 mm) bases shall be furnished as specified for intake applications to restrict entry of moisture and for all applications where rain and/ or snow may accumulate on the roof deck. Hood support members shall be constructed of galvanized steel and fastened so that the hood can be either removed completely from the base or hinged open. Birdscreens constructed of 1/2-inch (13 mm) galvanized steel mesh shall be mounted horizontally across the intake/discharge area of the hood. Gravity hoods shall be Fabra Hood model FGI for intake or model FGR for relief as manufactured by Greenheck Fan Corporation of Schofield, Wisconsin and/or in Rocklin, California, USA.