Attic and wall

A vapour control layer is a component that protects building structures against the penetration of water vapour from the interior into the thermal insulation. Its purpose is to safeguard mineral wool insulation and timber structures against moisture, which can lead to reduced thermal performance, mould growth, and material degradation. Eurovent® vapour control foils and membranes, such as Eurovent® CLIMA X, create an airtight barrier and support the correct performance of the entire roof–attic system.

Vapour barriers are characterised by very high diffusion resistance (high Sd values), which means they almost completely block water vapour transmission. Vapour control membranes with variable diffusion resistance allow controlled vapour exchange depending on conditions. The choice depends on the type of structure, ventilation system, and design requirements. The Eurovent® range includes both solutions, allowing precise selection for a specific building envelope. An example of a vapour control membrane is Eurovent® CLIMA X20, while Eurovent® CLIMA 100 is a vapour barrier.

Sealing tapes ensure full airtightness of the system by eliminating leaks around joints, profiles, roof windows, chimneys, and installation penetrations. Eurovent® products such as Eurovent® UNISAN provide very high adhesion to various building substrates, helping to maintain the required level of energy airtightness—especially in energy-efficient and passive buildings.

Membranes with variable Sd values, such as Eurovent® AKTIV, are recommended for structures exposed to periodic humidity fluctuations or in renovation projects where the risk of condensation is higher. These products “adapt” to conditions—blocking vapour in winter and allowing moisture to escape in summer. They are particularly suitable for the renovation of habitable attics.

Yes. An airtightness failure in the vapour control layer can lead to moisture accumulation in the insulation, deterioration of thermal performance, mould formation, and increased heating costs. A properly selected and correctly installed Eurovent® vapour control system improves energy efficiency and significantly extends the service life of the building.