Trapped moisture, either due to external intrusion or condensation from within, causes dampness, damages structures and can lead to mould that has serious health implications.
Finland’s Walki has developed a membrane that prevents humidity from getting to the structures of the building. Walki Active is a dual-purpose, vapour variable membrane made from polypropylene and a functional film layer. The variable water vapour barrier property makes Walki Active suitable for where there are big variations in temperature and moisture.
“When the air humidity is low, the vapour barrier property of our laminate is high, and when the humidity is high, the barrier is low,” says Juho Hyytiäinen, Walki’s technical service & development manager for construction.
In winter, when it is warmer indoors than outdoors, vapour tends to flow from inside to outside. Walki Active's functional film layer acts as a vapour barrier that hinders vapour from flowing flow into the structure during cold weather, the company says. In summer the polyethylene-copolymer film opens to allow water vapour to flow from outside to inside. Thanks to the membrane, moisture does not condense in the insulation layers inside the buildings.
“We see a great potential for Walki Active in the construction industry as the industry is constantly seeking new ways to improve both the quality and lifespan of buildings. The requirements for energy efficiency will also be tightened,” said Walki's CEO Leif Frilund.