Special DOUBLE AERATOR For Use In Insulated Roofs

A new concept is the double aerator, comprising two vents, for areas where both the concrete deck and the insulation need to be aerated and ventilated. Here a “special” 100mm high vent is placed onto the bare concrete beneath the waterproofing, and beneath the insulation; and another much higher “ideal” aerator is placed on top of the insulation.
http://www.wallbarn.com/products/roof-outlets-vents/roof-vents-aerators/special-double-aerator-for-use-in-insulated-roofs/