Before answering the question, here’s a quick refresher on rainscreen cladding systems.
In a nutshell:
- Rainscreen cladding systems are made up of an outer skin of panels, an air gap, insulation, and a support structure
- The air gap encourages a continuous circulation of air behind the cladding and helps the building ‘breathe’.
- Depending on the type of rainscreen panels being used, the standard air gap is between 25mm and 50mm
- Unventilated systems that use composite, high-performance insulated panels do not require an air gap
Rainscreen cladding systems are made up of four main features:
- An outer skin of panels – the rainscreen
- An air gap
- A support structure on the backing wall
Together, they make up what the CWCT (the Centre for Window & Cladding Technology) describe as a ventilated and breathable system.
How does a ventilated system work?
While the panels are the feature most people concentrate on (as an architectural feature on modern buildings), the air gap is arguably the most important.
Yes, the panels protect the backing wall from direct rain. But it’s the air gap that encourages a continuous circulation of air behind the cladding, drying out and expelling any moisture build-up, and helping the building ‘breathe’.
This, in turn, reduces the risk of damp and rot, and can extend the lifespan of a building.
Did you know?
Rainscreen cladding panels can also be used as aesthetic features on unventilated systems. Here, no air gaps are required. Instead composite, high-performance insulated panels are fixed to the steel structure to create a sealed system that provides all the protection the building needs.
How wide should the air gap be?
Elsewhere in the Knowledge Centre, you’ll learn that CWCT-tested cladding systems are neither airtight nor watertight?
In fact, effective rainscreen cladding systems can have open joints. Here, water ingress is reduced by allowing air to move between the inside and outside of the rainscreen, equalising the pressure and preventing water from being driven or sucked in. To work effectively, an air cavity of up to 50mm is advised.
So-called labyrinth joints create shadow-line gaps between panels as a design feature, but some wind-blown rain may still penetrate ‘up and over’ the joints. Here, an air gap of 38mm is recommended to create an effective, drying airflow.
Even if the panels are sealed, there’s always the possibility that some water droplets will penetrate cladding. Here, a 25mm wide air gap is sufficient to vent moisture from the backing wall and reduce condensation (as long as there’s also ventilation at the top and bottom).
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