Insulated membranes – the whys and the wherefores
It’s possible to insulate a building without using a vapour control layer or a breather membrane – there’s no legislation stating one has to be used. But what are the dangers of ignoring this step? After all - why spend money unnecessarily?
Architect Thomas Wiedmer, UK and Ireland technical director at ACTIS insulation, explains why it’s a good idea to use a vapour control layer when embarking on a new build and what to look for when choosing a breather membrane.
“While there is nothing in the building regulations stating that a vapour control layer or a breather membrane must be used they are recommended because they massively reduce the risk of interstitial condensation, guarantee air tightness and can protect the building from precipitation and wind driven rain if installed correctly,” he explained.
“Some vapour control layers, such as ACTIS HControl Hybrid, are dual purpose. While it is CE marked as a vapour control layer and has a high vapour resistance it also acts as an insulation, which means the thickness of the main insulation can be reduced to achieve the same required U-value. It is used on the warm side of any insulation material, behind the internal finish in roofs, walls and ceilings.
“A breather membrane has a low vapour resistance. Again, like the vapour control layer, some, such as ACTIS Boost’R Hybrid also act as insulation. This particular product is CE marked as a breather membrane but, like HControl Hybrid, is dual purpose. Reflective and watertight, yet vapour permeable it’s used on the cold side of roofs and walls. Because water vapour molecules are smaller than those in water droplets it lets moisture out but doesn’t let water in. It also helps improve the building’s air tightness. The membrane not only keeps damp out, it boosts thermal resistance, keeping heat in.”
Thermal modelling trials carried out by certification body BM TRADA have shown that ACTIS insulated membranes have a dramatic impact on counteracting thermal bridging and act as excellent thermal blankets.
Both membranes, along with their sister insulation product Hybris, are NHBC approved and have achieved LABC registered details which means they can be accepted by all LABC building control surveyors in more than 300 local authorities across England and Wales when used according to the certification.
Watch Boost'R Hybrid installation video