Vapour barrier under a sheet metal roof

Vapour barrier is an important part of roofs, as it helps with energy efficiency and protects the building from moisture.

What is a vapour barrier

Vapour barrier is used to protect against the penetration of water vapour into the roof structure. In the case of a sheet metal roof, it plays a significant role in protecting thermal insulation and the roof structure against moisture.

The main functions of the vapor barrier

• Prevents the penetration of water vapours

When warm and humid air comes into contact with a cold surface (such as a sheet metal roof), water condensation can occur. Without a vapour barrier, water vapour could penetrate the roof insulation, causing it to become damp and damaged.

• Prevents mould formation

Moisture in the structure can lead to the formation of moulds and fungi, which are harmful to building materials as well as to human health (causing allergies, respiratory problems and other disorders). A vapour barrier effectively prevents their formation.

• Improves energy efficiency

A vapour barrier helps to keep thermal insulation dry, which ensures its better efficiency. Moisture in the insulation could reduce its insulation properties and lead to higher heating costs.

• Extends roof service life

Due to moisture, insulating materials can quickly lose their functionality and begin to decompose. A vapour barrier extends the service life of roof insulation, as well as metal and wooden parts that could be damaged by moisture.

What materials is the vapour barrier made of

Vapour barriers are often made of polyethylene, aluminium foils, impermeable membranes or other synthetic materials with high vapor-tightness.

A vapour barrier is recommended for all roofs with thermal insulation, buildings with high humidity, flat roofs which are more prone to moisture retention, or for occupied atic space.