Vapour Control Layers
- Euroclass A2 (Limited-Combustible)
- Euroclass B (Flame-Retardant)
- General-application
- Advanced thermal performance
Vapour control layers and vapour barriers are used in roof and wall installations to ensure long-term protection to the building envelope. Air and vapour control layers improve the building’s air tightness and prevent moisture within the building’s warm air from reaching the insulation layer. Air and vapour control layers ensure that the building envelope is properly sealed to control ventilation and prevent heat loss in compliance with Building Regulations Part L. Installed on the warm side of insulation, vapour control layers protect insulates from interstitial condensation. This function minimises structural damage caused by trapped moisture - such as rot, mould, or weakening of materials.
Vapour control layers (VCLs) and vapour barriers are an essential component in modern construction, ensuring moisture control, energy efficiency, and long-term durability.
ITP manufactures a range of specialist VCLs and vapour barriers, engineered for high performance and durability. All products are fully compliant with relevant Building Regulations. We supply solutions with additional characteristics, such as limited-combustible and flame-retardant grades, high UV resistance, advanced energy efficiency which further enhance the protection of the building envelope.
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FlameOut Block Class A
A2-Rated Limited-Combustible vapour control layer
Our vapour control layer is glass-based woven scrim and an aluminium layer with a special protection coating to protect the aluminium layer from corrosion. The glass reinforcement scrim provides excellent tensile strength in wall and roof insulation. This advanced VCL is independently tested to British and international flame retardant standards. The product meets the Euroclass A2-s1,d0 fire safety required by other external wall elements such as cladding.
FlameOut Block Standard / FlameOut Block Premium
Class B Limited-Combustible vapour control layer
FlameOut Block is polyethylene-based vapour control layer with a mono-filament reinforcement scrim to provide excellent tensile strength in wall and roof installations. Available in two grades, this VCL is independently tested to British and international flame-retardant standards, with a Euroclass B,s1-d0 fire rating.
Powerlon VCL
General-Application air & vapour control layer
Powerlon VCL is a polyethylene-based vapour control layer with a mono-filament reinforcement scrim for tensile strength in wall and roof installations. Providing versatile use for a variety of buildings and ideal for commercial roofs, this high-performance VCL ensures that the building envelope is properly sealed to control ventilation, prevent heat loss and protect insulates from interstitial condensation.
Two grades are available:
- VCL 170
- VCL 250 (heavier grade)
Powerlon UltraBlock
Advanced Thermal Performance vapour control Layer
Powerlon UltraBlock is a range of thermo-reflective air barriers and vapour control layers incorporating encapsulated aluminium foil or metallised barrier layers to maximise energy efficiency. The reflective foil surface improves the insulation characteristics of the installation, reflecting heat back into the building.
Three grades are available:
- UltraBlock 200
- UltraBlock 250 (heavier grade)
- UltraBlock 300 (heaviest grade)
- VCL 250 (heavier grade)
What functions do vapour control layers provide?
Vapour control layers (VCLs) are essential barriers within buildings designed to prevent interstitial condensation, protecting structures from moisture damage and enhancing energy efficiency and comfort. By controlling the movement of water vapour, VCLs help maintain insulation effectiveness and structural integrity.
Water vapour, an invisible gaseous form of water, naturally moves from warmer indoor areas toward cooler external environments. When it encounters surfaces below the dew point, condensation forms, potentially damaging building materials and reducing insulation performance. VCLs mitigate this risk by controlling vapour passage, ensuring that any trapped moisture evaporates outward through external air circulation.
Typically installed on the warm side of insulation within walls, ceilings, and floors, VCLs block moisture from penetrating the insulation. To facilitate proper evaporation of residual moisture, external barriers like paints should be minimsed. Products like Ultrablock thermos-reflective vapour barrier membranes enhance thermal efficiency, contrasting with breather membranes, which allow controlled air passage.
VCLs are particularly important in modern building designs, where insulation creates cold spaces between the insulation and outer structures. By regulating moisture transfer, these layers prevent condensation from forming on cold surfaces, ensuring long-term structural health and energy performance.
Performance and safety requirements for vapour control layers
Performance Standards:
- VCLs must meet minimum performance requirements for air and vapor resistance, often expressed in terms of permeability.
- Materials are typically tested for water vapor resistance in accordance with BS EN 1931 (Water vapour transmission properties) and BS EN 12572 (Hygrothermal performance).
Fire Safety:
- The chosen VCL material must comply with relevant fire safety standards, such as BS 476 or EN 13501-1, ensuring it doesn't significantly contribute to fire spread.
- We recommend a minimum of Euroclass B,s3-d0 fire rating for VCLs.
- For best practice, we recommend the use of a VCL with Euroclass A2 fire rating in keeping with minimum requirements for other elements in the building envelope such as cladding.
Testing and Compliance:
Vapour control layers should be tested for resistance and permeability under BS 5250:2021 (Management of moisture in buildings). This standard outlines best practices for condensation risk assessment and VCL selection.
Reference British Standards:
- BS 5250:2021 - Code of practice for management of moisture in buildings.
- BS EN 1931 - Determination of water vapor resistance.
- BS EN 12572 - Hygrothermal performance testing methods.
Practical Considerations:
- Ensure compatibility with adjoining materials (e.g., tapes, adhesives, and sealants).
- Ensure the VCL works seamlessly with other building components, such as breather membranes and insulation, to optimise the performance of the envelope.
Related products
Stamisol A1
Engineered for durability, the Stamisol A1 is a Euroclass A1 Non Combustible breather membrane providing the highest possible fire and smoke protection.
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Safe One
SAFE ONE® is a limited-combustible breather membrane for use in vertical wall installations, behind closed or partially open façades and rainscreens.
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FlameOut Breathe
FlameOut Breathe is made from breathable, non-woven fabrics with superior self-extinguishing, flame-retardant properties. FlameOut Breathe FR is independently tested to EN 13501-1.
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- Phone: +44 (0)1347 825200
- Email: info@itpltd.com
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- York YO61 3FA, UK