25 x Felt Lap VentProduct Description
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, the Felt Lap Vent helps 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 & 220.127.116.11.
- Can be fitted at joist centres ranging from 400mm to 600mm
- 3,000mm²/m airflow
- 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
Initially it is recommended that one Felt Lap Vent be placed at every other rafter spacing, at low level (as near to the eaves as possible) on both sides of the roof space to ensure a cross flow of ventilation and monitor the condensation levels.
In extreme circumstances where the issue of condensation persists, additional Felt Lap Vents can be positioned in the roof space to increase the ventilation.
Regulations & Standards
BS 5250:2011 Control of Condensation in Building
275mm x 193mm