The underlay lap ventilator is designed for simple professional or DIY installation from the inside of cold pitched roofs where condensation is a problem.
It is designed to fit between the overlaps in the roofing underlay below the tiles or slates to introduce ventilation openings where there is no proper provision for roof space ventilation or existing ventilation air paths have been blocked, particularly when the loft insulation has been upgraded.
The shallow and tapered design of the panel suits all commonly encountered rafter spacings and allows for easy fitting between the roofing felt or underlay.
HD ULV-B