Many exterior wall constructions are designed with the thought that moisture will never penetrate the sealed envelope of a building, often enclosing a Stud Cavity. The Stud Cavity is, in theory, protected by a Weather Barrier on the exterior and a Vapor Barrier on the interior. This theory, in practice, is very hard to achieve because of the natural pressures at play in and around buildings.

An enclosed Stud Cavity has Greater pressures exerted on it from the Interior and Exterior Sides than what is exerted from within the cavity walls. Because it is practically impossible to maintain a completely uniform weather barrier on the exterior of a stud cavity, weak spots occur in the weather barrier. With the Stud Cavity having a much lesser pressure than the Exterior of the Building, these weak spots act to "suck in" water, air and moisture into the Stud Cavity. This locks in moisture in the Cavity Wall: creating a condition ripe for Mold and Mildew problems.

Today, many industry professionals are fully aware that eliminating all weak spots from the building envelope is not a real solution. Working with nature in lieu of against it is always a better option. Rainscreens act in tandem with nature.

Rainscreens eliminate the pressurized action that forces water into the weak spots, allowing water, air and moisture into appropriate locations during inclement weather. Moisture is then released naturally back into the atmosphere after precipitation has passed.

Rainscreens work because the most exterior layer of the wall (the drainage plane) acts as a pressure equalizer by allowing air to freely flow behind it. This gives the drainage plane equal pressures exerted on it from both sides, letting water freely fall down it's surface (in lieu of being sucked into it's surface).  
 

Insulation is open to this air space and is allowed to become moist in inclement weather. With dry sunny weather, this moisture is quickly evaporated with the help of the free flowing air in the air space.

The weather barrier is behind the façade wall (drainage plane) and is protected from direct exposure to the elements: expansion and contraction and damaging UV rays.

Geiger is here to help you create Rainscreens to meet the needs of your specific project. Centria offers a beautifully fully designed Wall System with their new MetalWrap System and Fundermax has endless design options for your Façade Screen. Feel free to contact Maureen Geiger with any of your rainscreen budget and design requirements.