Vapour Control Layers

What are Vapour Control Layers?

Vapour Control layered are used in modern building construction to prevent water vapour from the surrounding environment from passing through the layer. They are typically made from a polyethylene sheet and are often reinforced or combined with a reflective layer to improve their durability or insulation efficacy. They are designed to be used on the “warm side” of a wall or roof structure, in combination with a breather membrane, which is applied to the “cold side”. 

Types of Vapour Control Layers

We stock a wide range of Vapour Control Barriers with different levels of durability and efficacy to suit whatever the needs of your project. However, our range of Vapour Control layers can be divided into a few distinct groups:

Standard Grade Polythene VCL

Choose from our wide range of standard Polythene Vapour Control Layers. These are a standard polythene roll which is designed for affordable and simple installation.

Reinforced Polythene VCL

For a more durable finish, select a reinforced polythene VCL which is often suitable for flooring as welll as floors and roofs, and has greeted resistance to tears when installing. 

Gas Barrier and VCL

Used mostly in flooring, these are used to control the flow of harmful gases such as Radon and Methane into the structure from below. It is imperative that these are fitted with the correct airtight seal to achieve full efficacy. 

Reflective VCL and Radiant Barrier

Many of our SuperFOIL products function as both a VCL and Radiant barrier. Their reflective surface reflects heat - directing it back into the structure and directing external heat out - ideal for keeping buildings cool in summer as well as warm in winter. They are applied in the same way as a standard VCL, meaning they will increase thermal efficiency of a structure and work as a VCL, as long as an airtight seal is achieved.

How Vapour Control Layers Work

The primary function of a vapour control barrier is to limit the movement of water vapour through building materials. Water vapour naturally moves from areas of high concentration (warm, moist air) to areas of low concentration (cold, dry air). In a building, this often means moisture from indoor air trying to escape into the colder exterior during winter months or outdoor humidity penetrating the interior during summer. Typically, vapour barriers are installed on the warm side of the insulation (the interior side in cold climates) to prevent indoor moisture from reaching the insulation and exterior walls

Vapour barriers are typically made from materials with low permeability, such as polyethylene plastic. These materials create a solid barrier that prevents water vapour from passing through walls, floors, and ceilings. By blocking this moisture movement, the vapour control barrier helps maintain a dry and stable environment within the building. They must be properly sealed with jointing/lap tape to ensure a comprehensive airtight seal to ensure they are and stay airtight.