ARBO ARBOShield Pro Class A Air & Vapour Control Layer (AVCL) is a high-performance internal membrane designed to control air leakage and vapour movement within modern wall constructions, while also meeting stringent fire performance requirements. It is intended for professional use on projects where airtightness, moisture management, and regulatory compliance are critical.
The membrane achieves a Class A2-s1, d0 reaction to fire to EN 13501, making it suitable for high-rise and high-risk buildings such as residential blocks, schools, hospitals, and care facilities. This fire classification allows the AVCL to be used confidently within light steel frame (SFS) and other façade systems where internal fire contribution must be minimised.
From a building physics perspective, the primary function of the AVCL is to restrict warm, moisture-laden air from entering the wall structure. With a vapour resistance (sd value) greater than 2500m, ARBOShield Pro Class A AVCL provides an effective barrier against vapour diffusion, significantly reducing the risk of interstitial condensation. When installed correctly, it supports long-term durability of insulation, sheathing boards, and structural elements.
The membrane also incorporates a low-emissivity reflective surface. When installed facing a still air cavity of approximately 20mm, it can contribute to improved thermal performance, achieving a thermal resistance of up to 0.67 m²K/W. This supports improved overall U-values and helps reduce operational energy demand.
Installation location is critical. The AVCL must always be installed on the warm side of the wall construction. Fixing should be carried out using suitable mechanical methods, ensuring all joints have a minimum 100mm overlap. All laps, corners, window and door reveals, and service penetrations must be sealed using compatible ARBOShield Pro Class A High-Tack sealing tapes to maintain continuity of airtightness.
Careful detailing around penetrations such as cables and pipework is essential, as even small gaps can significantly compromise airtightness performance. The membrane should be kept clean during installation to ensure reliable adhesion of sealing tapes.
When specified and installed correctly, ARBOShield Pro Class A Air & Vapour Control Layer delivers dependable airtightness, effective vapour control, and enhanced fire safety for compliant, high-performance wall assemblies.
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