Rainscreen cladding is a layer of water-shedding material placed on top of existing walls and roofs. This cladding becomes the new outer layer of a building, and it is placed directly over the older outer layer. This two-layer design improves the water-shedding properties of the building and allows the insulation to work more effectively. Rainscreen cladding is commonly used on older buildings that are made of less weatherproof materials and have had more time to develop leaks.
Cladding is any process where one material is covered by another. In many cases, the covered material is a finished surface and cladding is meant as a protective layer. This is the case with rainscreen cladding—the outer walls of a building, or the building’s roof, is covered by a layer solely designed to shed water before it touches the original surface.
The installation of rainscreen cladding is a pretty straightforward process. First, a frame is attached to the existing outer surface—this frame is generally made of strips of wood that are less than an inch (about 2cm) thick. The new outer layer is then attached to this frame, creating a small gap between the two layers. The edges and corners are covered, giving the appearance of a single-layer wall. Doorframes and windowsills are extended to match the new outer wall.
The gap created when installing rainscreen cladding is very important. Since the cladding layer is not airtight, the air pressure inside the gap is the same as the pressure outside. This is in contrast to a standard building, where the inner pressure is often different from the outer. The equal pressure will neither draw air in nor give it cause to escape, meaning the water running over the surface of the building will do the same.
Since the gap is filled with air, this has a direct impact on the building’s outer-wall insulation. Without the cladding, when water flows over the surface of the building, it will draw thermal variations from the walls and roof. If the inner building is warmer than the outside, it will pull away heat; if it is cooler, it will steal some of that. The air-filled opening acts as a natural buffer between the inside and the outside. Since the water no longer touches the building directly, it steals less temperature.
Should water penetrate the cladding, it is often less problematic than if water penetrates a standard wall. Since the gap allows air flow, it will dry quickly; inner walls restrict airflow and they will stay wet longer. In addition, most cladding systems have a method of releasing water rather than trapping it inside. When water gets into a house, it often soaks into the insulation, reducing its effectiveness until it dries out.