If your facility is located in a fairly wet climate, you could benefit from a rainscreen. Rainscreens have been around for more than 20 years in the U.S., but thanks to recent advances, their popularity is starting to boom.
Rainscreens provide a protective envelope that deters rainwater intrusion into exterior walls, but they offer more than just protection from water damage. They also offer an effective means of managing:
- air infiltration
- heat transfer
- negative wind pressures
- vapor transmission
What is a rainscreen?
A rainscreen is an attached-rear-ventilated cladding to an existing building. Similar to the way a tent fly works, a rainscreen works by providing an outer layer to keep out the rain. Rainscreens also feature an inner layer to provide thermal insulation, prevent excessive air leakage, and carry wind loading. This insulation moves the dew point to outside the air/vapor barrier, which eliminates moisture from the facility’s wall, preventing mold development.
The outer façade of a rainscreen can be made from a number of materials, including metal, wood, fiberglass, terra cotta, fiber cement, GFRC (glass fiber reinforced concrete), concrete, and more.
Rainscreens come in three different varieties: vented, drained and vented, and pressure equalized.
This is really a misnomer, because these systems don’t actually allow for ventilation. Vented rainscreen systems are mainly used with a render and are not recommended for buildings taller than four stories. These systems work by using a warm cavity which provides a dew point close to the outside, ensuring a very low risk of moisture penetrating the system. Vented systems feature:
- Warm cavity, no ventilation
- Cavity open at the bottom only
- Drainage, but no convective ventilation
Drained and Vented Systems
Also not recommended for use on buildings more than four stories high, these systems require a cavity opening at the top and bottom that provides drainage and promotes convection ventilation. Excessively high drained and vented systems should be avoided. These systems are not watertight, and an overhang is generally used to protect the cavity from the elements. The features of a drained and vented system include:
- Protect backing structure with moisture barrier (VCL)
- Non-hygroscopic or closed cell insulation (PIR or Rockwool)
Pressure Equalized Systems
With these systems, water ingress is reduced by equalization of internal and external pressures. These systems are commonly used for buildings taller than four stories, because they allow wind to blow in behind the rainscreen panels, equalizing the pressure, and resulting in a low wind load on the rainscreen itself. Pressure equalized systems feature:
- Compartmentalized cavities that allow for the rapid ingress and egress of air
- Compartmentalization also controls pressure, which can prevent the spread of fire
- Draining above compartment levels
Most structures can benefit from rainscreens thanks to the greater moisture protection and added durability provided to an otherwise ordinary wall. Plus, a compromise in a rainscreen system will result in far less damage and less costly repairs than a similar compromise to regular external wall.
For more information on rainscreens and protecting your facility, contact Vanguard Resources.