The foremost layer of defence a pitched roof has against the elements are tiles. But the second layer is roofing felt, and the most common type of roofing felt in the modern day are breathable membranes or breather membranes. Roofing felt is installed directly under the tiles, and serves to catch any moisture that manages to penetrate the tiles and redirect it to the gutter.
Breather membranes are a type of roofing felt that represents a significant improvement on traditional membranes. Whereas traditional underlay might use materials like polyester nowadays advanced breather membranes use materials like polypropylene which make it a superb roofing material.
The most impressive thing about breather membranes is how much they improve airflow in your loft. If your air remains stagnant in your loft then it can contribute to condensation. Roof vents are needed to introduce airflow, and breather membranes can help immensely in this regard (though vents will still be needed). Without these measures, condensation can lead to rot and serious, chronic damage to both your roof and the rest of your house.
Whereas non-breather membranes do not permit the flow of air, breather membranes do. Even more impressive is *how* they let air through – water vapour can go through one direction, out from the loft and towards the tiles. However, it cannot go through the other way. This allows the loft to expel water vapour without risking it coming back in.
Because of these features, breather membranes are a must in “warm roof houses”. These are where the roof itself is insulated, and the loft area is warm.
What Breather Membranes are Right for you?
At ERoofing we stock an excellent selection of roofing underlay including all of the best modern breather membranes. Each has different features, usually specialising in cost-effectiveness, durability or vapour expulsion.
Cromar Vent 3 – Classic, Light and High Performance
The three varieties of Cromar Vent 3 – all distinguished by their red, green, and blue colouration respectively – are an inexpensive, lighter form of underlay. Light in particular is excellent at felting small buildings like sheds. Classic and High Performance are more expensive and better suited for houses.
Permavent Black Breather Membrane
Permavent Black Breather Membrane is another lightweight felt. It’s made using a special process that combines all the layers into one. Alongside its black colour, this makes for a very discrete roofing felt that can be used on smaller buildings or ones where the felt will be visible without being obnoxious.
Klober Permo
Klober Permo is the felt you install when you are dealing with serious condensation. It might seem expensive upfront, but it’s permeability actually eliminates the need for dedicated felt lap vents, offsetting the expense somewhat.
Marley Vapour Permeable Underlay
Marley’s Vapour Permeable Underlay is one of the most heavy-duty breather membranes on the market. It conforms even to the most stringent UK wind zone standards thanks to its multi-layer structure and integrated tape system.
Proctor Roofshield
Proctor Roofshield is the most high-end roofing underlay available. It’s certainly an investment, but it provides all-around performance metrics that are second to none. Like Permo, you’re also saving on having to install felt-lap vents with its high permeability.
