What is an Air & Vapour Control Layer (AVCL)?
An Air & Vapour Control Layer (AVCL) is a membrane used throughout construction projects and it is designed to protect building elements from degradation by restricting the movement of water vapour from inside a building to within the building structure (interstitial condensation). An AVCL, therefore, helps prevent interstitial condensation.
What is interstitial condensation?
Condensation will occur where the water vapour in warm air inside the property condenses into liquid form – this occurs when there is a temperature difference between the air and the surface it lands on. Condensation which occurs within elements of the building fabric is called interstitial condensation and it can occur within walls, pitched and flat roofs.
Where should they be specified?
Framed structures
For framed structures such as timber frame and light gauge steel frame systems, an AVCL should be used on or near the warm side of the insulation.
Pitched Roofs
For pitched roofs, an AVCL should be used on the warm side of the insulation for both warm and cold roofs.
Flat roofs
For flat roofs, an AVCL should be used on the warm side of the insulation for warm deck flat roofs Cold deck flat roofs are not recommended and an alternative form of flat roof should be adopted.
The above is not an exhaustive list of every situation where an AVCL is required, however it should provide some guidance for the most common locations for an AVCL to be located.
Different types of AVCLs
We’ve recently seen a surge in air and vapour control membrane products used on site. These AVCLs are generally broken down into two distinct groups, ‘standard’ for traditional housing applications and ‘non-combustible’ for high-rise applications.
To help specifiers select the correct AVCL for their needs, we have produced this useful resource PDF.
In addition, Grayson can also offer a range of training, toolbox talks and CPD’s via our field-based experts.
Summary
In summary, an AVCL is a membrane used throughout construction projects and it is designed to protect building elements from degradation by restricting the movement of water vapour from inside a building to within the building structure.
To find out more, contact our knowledgeable and experienced experts on – 08448 50 40 50
