Ventilated rainscreen systems

A ventilated rainscreen is not a single material, but a system composed of multiple layers. each with a specific role in protecting the building. As the Rainscreen Association of North America (RAiNA) defines it, at minimum such a system has "an outer layer, an inner layer, and a cavity between them sufficient for the passive removal of liquid water and water vapor."

The rainscreen system has five key components:

• Outer Cladding Panels: The visible exterior layer – often fiber cement panels  –  form a durable, water-shedding skin. These panels take the brunt of weather exposure (rain, wind, UV radiation) and provide an aesthetic finish to the building. In a ventilated rainscreen, the panels are usually installed with small open joints between them (open-joint cladding) (LINK TO BLOG).

• Supporting Subframe: Behind the panels, a structural support system of vertical and/or horizontal rails, girts, or clips creates the necessary stand-off and attaches the cladding to the building structure. Typically made of alumnium, galvanized steel, or wood, this sub-construction holds the panels securely.

• Ventilated Air Cavity: A continuous gap or cavity (often ~¾” to 1” or more in depth) is intentionally maintained between the outer cladding and the inner layers. This air space is open to the outside at the bottom (and usually at the top) of the facade, allowing air to flow in and out.

• Insulation: In many ventilated rainscreen designs, a layer of thermal insulation is installed on the exterior side of the wall, within the system (often directly against the inner wall or between the subframe members.) This exterior insulation, commonly rigid mineral wool or foam boards, enhances the wall's thermal performance by providing continous insulation.

• Inner Backup Wall & Weather Barrier: This is the actual structure of the building (e.g. wood or metal studs with sheathing, or a concrete block wall) along with a weather-resistive barrier on its exterior face.

"Minding the gap"  - as building scientists often say - is critical to a wall’s longevity. The ventilated cavity behind rainscreen panels performs several key moisture management functions that keep the wall dry and damage-free.

• Wetting Prevention (Capillary Break): By separating the outer cladding from the inner wall, the cavity creates a capillary break. In a conventional wall, if cladding sits directly on a wall, water can wick through small cracks by capillary action. In a ventilated rainscreen, any rainwater that penetrates the panel joints or porous cladding cannot easily jump the gap to reach the inner wall. The air space short-circuits the wicking of moisture between layers, so the structural wall stays far drier.
• Drainage Plane: The open cavity acts as a free drainage path. Gravity ensures that any bulk water (rainfall, etc.) that does get past the panels drains downward and outward without hitting the inner wall hammerandhand.com. The inclusion of through-wall flashings and weep openings at the base of the cavity allows water to safely exit. Essentially, the rainscreen design catches water that gets in and funnels it out before it can do harm. This is a major improvement over face-sealed walls where a single line of defense must stop all water. Here, even if the outer layer leaks, the system still manages the water.
• Ventilation & Drying (Airflow Mechanism): When vents or gaps are provided at the bottom (intake) and top (exhaust) of the cladding, the cavity becomes a ventilated channel. Warm air tends to rise and exit at the top of the facade, drawing in cooler air at the bottom – a stack effect that continuously circulates air through the cavity behind the panels. This airflow can create hundreds of air changes per hour in the gap, quickly removing moisture vapor.

These three mechanisms – deflection, drainage, and drying – are why ventilated rainscreen systems are considered a best-practice for moisture management in building enclosures. Studies have shown that walls with ventilated cavities dry many times faster than walls without, dramatically improving resilience to moisture (LINK). In climates with heavy rain or humidity (for example, coastal regions or the Pacific Northwest), ventilated cladding is especially beneficial to prevent long-term dampness in walls. In fact, experienced builders in wet climates “swear by ventilated cavities” because they know even well-detailed walls will eventually get some water ingress, and giving that water a way out is the key to avoiding rot.  

The impacts of a ventilated rainscreen facade go beyond just keeping water – they fundamentally enhance the durability and lifespan of the building envelope:

• Extended Materials Life: By protecting the inner structure and even the cladding itself from prolonged moisture exposure, ventilated rainscreens help prevent the deterioration of building materials. Key structural elements (like sheathing, framing, and connectors) stay dry and avoid rot or corrosion over time.
• Better Indoor Quality and Structural Health: A dry building envelope means a healthier building. By stopping mold growth within wall cavities, ventilated rainscreens protect indoor air quality (no hidden mold spores seeping into occupied spaces). They also prevent unseen long-term damage – the kind that might not be obvious until it causes a structural failure or costly repair. Think of the rainscreen as a form of preventive medicine for the building: it significantly reduces the risk of the envelope suffering a “sick building syndrome” or structural decay from moisture.  
• Robust Weather Resistance: The layered defense of a rainscreen makes the whole facade more robust against all weather conditions. The outer layer takes the brunt of wind, rain, snow, and UV radiation, sparing the inner wall from those forces. Even in extreme weather or wind-driven rain, the dual-layer system holds strong: the outer panels might get wet, but the inner wall remains protected behind its ventilated buffer zone. Many rainscreen claddings (like fiber cement panels) are also noncombustible, adding fire safety to the envelope’s resilience.
• Architectural Flexibility without Performance Trade-off: Traditionally, designing a flashy facade (with complex joints, varied materials, etc.) could conflict with making the wall weathertight. Ventilated rainscreen panels decouple the aesthetic outer layer from the inner waterproof layer, meaning architects have greater freedom to use creative cladding patterns, open-joint designs, and a mix of materials without compromising the envelope’s integrity.  EQUITONE panels, for instance, come in large format sizes and different colors and textures, enabling bold facade designs; and since they’re used in rainscreen applications, the dramatic facade still meets the highest standards of weather protection.
• Futureproofing and Sustainability: Incorporating a ventilated rainscreen panel system is an investment in the building’s future. As building codes tighten on energy efficiency and moisture control, rainscreens are a forward-looking solution – many new high-performance buildings already include them, and older buildings can be retrofitted with rainscreen cladding to solve water intrusion issues.