Rigid Air Barriers

Rigid air barriers (or external sheathing boards) are essential components often incorporated within open facade and rainscreen systems, positioned behind the rain screen/cladding and ventilation cavity. They act as a protective skin over the internal lining and insulation, providing a proven alternative to flexible building membranes. These barriers are typically used in mid to high-rise buildings subjected to challenging site conditions but can also be effectively utilised in low-rise buildings.

Key Features of Rigid Air Barriers:

• Condensation Management: Rigid air barriers offer effective condensation management similar to Class 4 vapour permeable membranes. Their vapour permeability allows moisture to escape, reducing condensation buildup.

• Durability: When tapped at the joints and continuously sealed, rigid air barriers become a secondary weathertight layer that can be left exposed for extended periods during construction. This makes them particularly useful in maintaining the integrity of the building envelope.

• Material Composition: Unlike pliable membranes, rigid air barriers are typically made from fibre cement sheets or similar rigid substrates. This gives them superior performance against wind forces or wind washing and, in some cases, allows them to be deemed non-combustible.

• Additional Protection: An additional membrane can be adhered to the rigid air barrier if further protection is needed. This enhances their role in a comprehensive air-tightness strategy.

• Thermal Performance: Although rigid air barriers themselves do not provide thermal performance due to their material thickness (typically between 13 – 16 mm), they contribute to a broader thermal and condensation management strategy. By promoting dryer wall systems, they can help improve overall R-values in practice.

Rigid air barriers are an integral part of modern construction, especially in environments where high performance and durability are required. Their ability to manage condensation, withstand harsh weather conditions, and enhance overall building performance makes them a preferred choice in both high-rise and low-rise buildings.