If you've noticed condensation in your loft, improving roof-space ventilation may be one of the things you need to consider.

For certain existing roofs, felt lap vents offer a straightforward way to introduce additional airflow without removing roof tiles.

What Is a Felt Lap Vent?

A felt lap vent is designed to fit between overlapping sections of roofing felt or underlay from inside the loft.

The vent separates the lap slightly, creating an opening that allows additional air into the roof space.

This makes them particularly useful for remedial work on suitable existing roofs.

When Are Felt Lap Vents Useful?

Felt lap vents may be considered where existing roof-space ventilation needs enhancing.

For example, they can be useful when:

• Condensation is appearing within a cold roof space
• Existing ventilation is limited
• Ventilation paths have become restricted
• Additional loft insulation has affected airflow around the roof space

Because they're installed from inside the loft, the roof covering doesn't normally need to be removed to fit them.

Are Felt Lap Vents Enough on Their Own?

Not necessarily.

Felt lap vents are designed to enhance existing ventilation through suitable felt or membrane laps. They shouldn't automatically be treated as a replacement for correctly designed eaves, ridge or other required roof ventilation.

The amount and type of ventilation required will depend on the roof construction, existing ventilation and the specific problem you're trying to solve.

What Should You Check Before Installing Them?

Before choosing felt lap vents, check the roof construction and underlay to make sure the product is suitable.

It's also worth checking that existing ventilation hasn't simply become blocked by insulation or other obstructions.

If you're unsure what's causing moisture in your loft, investigate the source first rather than assuming that adding more vents will solve the problem.

Shop Felt Lap Vents

At Vents Direct, we stock felt lap ventilation solutions from specialist roofing manufacturers including Timloc and Hambleside Danelaw.

Browse our Felt Lap Vents range to find the right solution for your roof.