Ask the Experts: What is Breather Membrane?

‘What is breather membrane?” is a common question the PermaRoof UK experts get asked when discussing flat roofing projects. It is an important part of pitched roof projects, and not used in flat roofs. Let’s take a look at it in more detail.

What is a breather membrane?

Breather membranes are used in roofing to minimise condensation by allowing water vapour to escape without needing additional ventilation. They are also commonly used within walls to help with air tightness as well as minimising condensation within the fabric of the building.

They are manufactured to be lightweight, waterproof, yet still permeable and breathable so that they let water vapour through. The best breather membranes are also well UV stabilised.

Why do you need breather membrane?

Breather membrane is needed to minimise the effects of condensation in roofing. Once the temperature reaches the dew point and drops below it, the air will release the moisture and this needs to be allowed to escape.

This is a process that is repeated throughout the life of the roofing as the vapour pressure rises and falls from all the permeable materials in the roof. Incorporating adequate insulation and vapour control in warm roof constructions will prevent the build-up of condensation by allowing any vapour to escape.

Aside from the reduced need for additional ventilation, there are a wider range of benefits:

• Reduce the heat loss through the roof space by up to 25%
• Improve the energy rating
• Help to eliminate the thermal bridges at the eaves and across timbers
• Save money on ventilation products
• Improve the air quality inside the home

The difference between ‘breather membrane’ and a ‘vapour control layer’

While both types of products serve a similar purpose, there are some key differences between them.

Breather membrane is installed on the outer side of the insulation. This allows water vapour to escape from the roofing, but also keeps wind-driven rain, insects and other debris out.

A vapour control layer (VCL) is designed to reduce water vapour transfer on the inside of the building. The VCL is installed typically on the inner side of the insulation. It can sometimes be incorporated into certain types or brands of insulation.

Further reading:

Other FAQs about breather membrane

Can you use breather membrane in a flat roof?

Breather membranes are not suitable for flat roofing. A VCL or insulating board offers a better approach for flat roof projects.

What kind of damage does condensation do to a roof?

Condensation can wreak havoc in the structure of the roof over time:

• Rotting timbers
• Lost thermal performance
• Mould

Is breather membrane hard to install?

The principle of installing breather membrane is straightforward, however, it is important to get it right. There are building regulations that express the minimum requirements for air leakage and other considerations. It is wise to seek professional advice if you’re unsure about installing to regulations.

How to choose the right membrane for a new build

The first step is to understand the building regulations, especially if you’re working on a new building. These regulations mean that you need to consider wind lift in your location and ensure you buy a suitable membrane. Note that across the UK, manufacturers can categorise breather membrane by region.

Related products to buy online:

How to choose the right membrane for a new build

The first step is to understand the building regulations, especially if you’re working on a new building. These regulations mean that you need to consider wind lift in your location and ensure you buy a suitable membrane. Note that across the UK, manufacturers can categorise breather membrane by region.

We hope we have helped you with our explanation of what a breather membrane is and some of the benefits. If you have a further question about how to plan, prepare, install or any other aspect of your roof project, please visit our FAQs page, give our expert team a call on 01773 608 839 or use the live chat for a quick query.

Other articles about flat roofs:

PermaGroup has established links with some of the biggest names in our industry thanks to our reputation of excellence. Read more about becoming a supplier or stockist here.