Timloc 5560 Felt Lap Vents
Timloc Felt Lap Vents
Attic or loft condensation is normally spotted either in the winter months, or after installing new loft insulation.
All homes generate moisture from everyday activities like cooking and showering. When this moisture condenses in a cold loft it can eventually lead to costly problems like rotten roof timber.
Condensation in the loft is usually caused by inadequate ventilation. This can often be remedied quickly and easily if your loft has traditional lapped membrane or roofing felt behind the tiles.
The Felt Lap Vents are fitted inside the loft by simply clipping individual vents onto the edges of the felt or membrane close to the eaves.
Each felt lap vent creates an air gap delivering up to 3000mm2/m of ventilating airflow. When combined with existing roof space ventilation, fitting evenly spaced lap vents on both sides of the loft will fix most loft condensation problems.
Features and Benefits
- To increase the level of ventilation in a roof space by separating lap joints in the roofing felt/membrane.
- Remedial solution for combating condensation in cold roof voids
- Can be fitted retrospectively after increased loft insulation
- Discrete profile design
- Easy installation
- 2 spring clips to secure each unit in place Technical Information
- 3000mm2 additional free vent area per unit
- Suitable for rafter spacings from 400-600mm centres
- Designed only to enhance existing ventilation via felt/membrane lap joints
- Pack of 10 or 150
- Consideration must be given to increased risk of wind uplift and driving rain resistance outlined in BS5534:2014
- Dimensions - 280mm Length, 205mm Width, 19mm Depth
Quality
Manufactured to British Standards: BS EN 9001 and BS EN 14001
Material and Colour Choice
- Injection Moulded recycled Polypropylene
- White
How Many Vents Do I Need?
The number of felt lap vents can be worked out using the following formula:
Selecting the amount of airflow, then dividing the roof length by the spacing (in meters) indicated below.
| Free Flowing Airflow | Felt Lap Spacings | |
| Millimetres | Meters | |
| 5000mm/m ² | 600 | 0.6 |
| 10000mm/m ² | 300 | 0.3 |
| 15000mm/m ² | 120 | 0.12 |
For Example:
For a roof that is 7m requires airflow of 10000mm/m ²
7/0.3 = 23.333 or 24 felt lap vents evenly spaced.
For roof spaces that require more than the 15000mm/m ² the spacings half for each additional 5000mm/m ²
Please note these are designed as a remedial solution to roof ventilation and do not meet the standards for permanent roof space ventilation on their own and felt lap vents may adversely affect wind uplift of slates and tiles. For more information, please see our blog on the changes to BS 5534:2014 or see BS 5250 Code of Practice for Control of Condensation in Buildings.
