Permavent offers the most competitive air & vapour permeable membrane in the UK. Permavent APEX is a 3 layer breather membrane for use as a pitched roof underlay. Permanent APEX is a vapour and air permeable membrane providing unique condensation control which eliminates the need for low or high level ventilation. Permavent APEX also provides a secondary barrier to water ingress. All of our membranes are manufactured using the latest technology. All membranes are fully UKCA certified and are rigorously tested to comply with European Harmonised standards. Our membranes are fully tested by BRE.