A ventilated rainscreen is an ACP or aluminium facade hung a short gap off the wall, with open or baffled joints, so most water runs off the panel and any that gets behind drains and dries in the ventilated cavity. The cavity — usually 25–50mm — is what keeps the structural wall dry and prevents the damp, mould and staining you get when cladding is stuck tight to the wall. It is how modern aluminium facades are meant to work.
What a rainscreen actually does
A rainscreen accepts that some water passes the outer skin and manages it, rather than trying to make the skin perfectly sealed. The ACP panels shed most rain; the ventilated cavity behind drains the rest down to a flashing and lets air movement dry the wall. The building’s weather line is the insulated, membraned wall behind — not the panel itself.
Cavity depth and ventilation
The cavity is typically 25–50mm, formed by the support brackets and rails that hold the cassettes. It must be open top and bottom (and at floors) so air can move and dry it, with insect mesh at openings. Too shallow or blocked, and it cannot drain or breathe; too deep wastes space. The bracket system sets this depth.
Open joints, baffles and drainage
Rainscreen joints are open or fitted with baffles that stop wind-driven rain while letting the cavity vent. Water that enters runs down the back of the panel and the cavity face to a base flashing that throws it clear. Design the joints, flashings and cavity as a system — panels alone do not make a rainscreen.
Why it prevents damp and staining
Stick cladding tight to a wall and trapped moisture causes damp, mould and the water-staining that shows on facades. A ventilated cavity keeps the wall dry, stops interstitial condensation, and lets the aluminium panels — which do not rust anyway — perform for decades. It is why quality ACP facades are built as drained, ventilated rainscreens, not glued-on skins.
Frequently asked questions
What is a ventilated rainscreen? An ACP or aluminium facade hung off the wall with a ventilated cavity, so water drains and dries behind the panels instead of soaking the wall.
How deep is the rainscreen cavity? Typically 25–50mm, set by the support brackets, and open top and bottom so air can dry it.
Do rainscreen joints let water in? Some passes the open or baffled joints by design; the ventilated cavity drains it to a base flashing that throws it clear.
Why not fix cladding tight to the wall? Trapped moisture causes damp, mould and staining. A ventilated cavity keeps the wall dry and lets the facade last decades.
Related: ACP fixing methods · aluminium curtain wall systems · ACP buyer’s guide.
Talk to the factory: GSM BuildTech (Beijing Guanshimao Technology Co., Ltd.) makes insulated aluminium panels, FR aluminium composite panels, aluminium ceilings, standing-seam roofing and PVDF aluminium coil in Tianjin, China. Email sales@insulatedaluminumroof.com or WhatsApp +86 155 2274 6824 for factory-direct pricing. See the technical reference & FAQ.