Abstract: An improved, ventilated roof construction for flat roof installations substantially decreases damage caused by roof leaks that allow water to settle into the roofing substratum and insulation. A grid or perforated plate is supported in spaced arrangement above the underlying roofing support deck and immediately beneath the exterior roofing surface to define an air passageway or air duct therein. The grid allows evaporation of moisture from the insulation layer therethrough as air circulates thereunder. A plurality of conduits leading from the grid to the exterior roofing surface provide means for vacuuming accumulated water from the interior roofing structure to avoid damage thereto, or to pump water into the interior roofing structure to extinguish fires.