AIRFLOW Over Fascia Vent This slim line over fascia ventilator ensures a flow of air into the roof space between the felt and the fascia board. The product is designed with a smooth leading edge allowing it to sit discreetly on top of the fascia board beneath the felt. 25mm vent provides the equivalent of 25,000mm² per metre. Products are robust enough to be used with any roof tile no regardless of the profile and can be fitted with plain tiles or slates. Designed with clear fixing points both versions of the Manthorpe Over Fascia vent come complete with fly-screen and will not crush or distort during fitting.