Refurbishment ventilator for existing roof spaces to increase the level of ventilation in a roof space by separating lap joints in the roofing felt/membrane. Also a remedial solution for combating condensation in cold roof voids and can be fitted retrospectively after increased loft insulation. Discrete profile design Easy installation 2 clips to secure each unit in place Manufactured to British Standards: BS EN 9001 and BS EN 14001 Injection Moulded recycled Polypropylene White Allowing ventilation between roofing felt/membranes is secondary to eaves and/or ridge ventilation Lap vent simply slots between roof felt/membranes laps Position the lap vent clips facing down to hang on the edge of the roofing felt/membrane when in position Install one lap vent into every alternate rafter space at low level If further ventilation is required, install one lap vent into every rafter space at low level and/or into lap joints at higher levels The lap vents should be fitted to both sides of the roof space in order to provide cross-flow ventilation Installing lap vents alone will not meet minimum roof ventilation requirements. For guidance and regulations on roof space ventilation please refer to British Standard BS5250 Calculate quantity of lap vents based on the level of ventilation required For typical installation allow 1 lap vent per alternate rafter spacing at low level Increase ventilation by allowing additional lap vents at high level For maximum ventilation allow lap vents to every rafter spacing