A TLX Guide to Breathable Membranes


Why do you need breathable membranes?tlx uv 10 breather membrane

Breathable membranes are an integral part of any roof or wall build up as they protect the living space of a building from the external environment. Essentially, they act as an additional waterproofing layer to accompany the external cladding, a very important requirement for any building exposed to the unpredictable British climate. Yet there are other benefits to breathable membranes, they are also air permeable, meaning that any warm, moisture filled air rising from the inside can escape. Therefore, the risk of condensation is significantly reduced.

What makes a good breathable membrane?

The mark of a good breathable membrane is its ability to provide a substantial resistant barrier between the internal and external environment. Here is a list of characteristics associated with breathable membranes:

  • Waterproof
  • Air permeable
  • Breathable
  • Lightweight
  • Hard wearing
  • Slip resistant
  • Easy to install
  • Provide protection from adverse weather conditions
  • Provide wind resistance to limit the movement of air

tlx uv 15 breather membraneWhy are breathable membranes so important?

Space savers

They offer a distinct benefit compared with non-breathable membranes as they don’t require a 50mm ventilated air space beneath them, therefore they are an excellent space saving solution, especially in very old buildings where internal space is tight.


The benefits of a property fitted with a breathable membrane compared with 1f felt are remarkable in terms of their energy saving capacity. Since a 50mm ventilated air space isn’t required when a breathable membrane is installed above the rafters in a roof, this frees space within the rafter space for additional insulation and makes for a far greater thermally efficient structure.  This build-up can improve thermal performance by 87% and reduce CO2 emissions by 57%.

Limit condensation risk

TLX UV Breathable membranes can significantly reduce the chance of condensation build up in a roof or wall space. Although they are completely watertight, they will allow air to pass through them, so any vapour carried within air particles can be passed through the roof or wall space and outside. Our TLX Gold multifoil insulation takes full advantage of this, having an integrated UV25 breathable membrane to prevent condensation whilst the underlayer is a shiny breathable surface which reflects heat.

What is the difference between TLX UV10 UV15 and UV25?tlx uv25 breather membrane

Here at TLX Insulation Ltd, we manufacture 3 different grades of breathable membranes: the UV10, UV15 and UV25, each suitable for renovation and new build projects alike. The different grades correspond with variations in tensile strength, UV10 being the lightweight material, UV25 being the heavy-duty option and UV15 occupying the middle ground.

Below is a table giving the weights of each product in g/m2:

How to install a breathable membrane?

The correct installation of breathable membranes in accordance with the manufacturers instructions is paramount in ensuring its efficiency. Below is a step-by-step guide on how we recommend fitting them:

1. Extend an eaves guard into the gutter and overlap the eaves guard with the UV breathable membrane. *The printed side must face uppermost.

2. Install the breathable membrane parallel to the eaves, starting at the eaves and working up the slope of the roof.

3. Allow a drape of 10mm in-between the rafters.

4. Fix counter-battens (at least 25mm thick) over the membrane and through to the rafters so that there is an uninterrupted air space between the underlay and the roof tiles or slates.

how to install a uv membrane

How long does a breathable membrane last?

Our TLX Breathable membrane range is fully BBA approved for use within roofs and walls. The products will be virtually unaffected by the normal conditions found in a roof space and will have a life comparable with that of traditional roof tile underlays, provided they are not exposed to sunlight for long periods.

If you would like further information regarding the suitability of TLX UV breathable membranes for your upcoming project, don’t hesitate to contact our product scientists on the below number.

tlx insulation technical help line