Pack 20 Roofing Felt Lap Vent Stops Loft roof Condensation/Attic Space Ventilation Airflow

• The Manthorpe G630 Felt Lap Ventilator is a refurbishment product that is designed to increase the amount of ventilation into existing roof spaces with a lapped felt/ membrane construction.
• The product is intended to be fitted retrospectively to properties that have had additional loft insulation recently installed. The vent will help to combat the problem of condensation build up caused by the extra insulation by adding additional ventilation into the roof space.
• The product will not meet the requirement for roof space ventilation solely on its own it will only provide airflow through the felt laps into the batten void.
• The product has been designed as a remedial solution to help overcome the build-up of condensation in the roof space, however like all products that open the felt lap to provide ventilation it does not meet the code of practice BS 5534:2014+A2:2018 6.2.1.1
• The specifier or user should be aware that the opening of felt laps on the roof may adversely affect the driving rain resistance of the slates, tiles or shingles, as well as increase the wind uplift forces acting on them.

The Manthorpe Felt Lap Vent is a refurbishment product designed to increase the amount of ventilation into existing roof spaces. Usually fitted retrospectively to properties with additional loft insulation recently installed, however the Felt Lap Vent will help to combat the problem of condensation build up in any roof space with a lapped felt/membrane construction. The specifier should ensure that the opening of felt laps on the property will not adversely increase the wind uplift load on the tiles/slates or the driving rain resistance of the roof, for more information see BS 5534:2003, 5.8.1 & 6.2.1.1. - 3,000mm² airflow per G630. - Can be fitted at joist centres ranging from 400mm to 600mm. - Easy to fit, the tapered lead in helps to slot the product between the felt laps. - The 3 felt clips help secure the product in place even if the edge of the felt is degraded. Installation: - Initially it is recommended that one ventilator be placed into the laps in every other rafter bay, down at low level (as near to the eaves as possible) and on both sides of the roof space to ensure a cross flow of ventilation. - In extreme circumstances, additional ventilators can be positioned in the vacant felt laps to increase the overall amount of ventilation provided. - Only one product should be positioned into a single felt lap. If additional vents are required, then more vents can be placed into the other felt laps within the same rafter spacing at higher intervals. - The product can be installed in roof spaces with rafter spacings ranging from 400mm to 600mm. - Each unit will provide 3,000mm² of free airflow into the batten void. - For further information on the recommended ventilation requirements for roof spaces refer to BS 5250 Code of Practice for Control of Condensation in Buildings.