A History of Rainscreens

NorwayAbout 70-years ago in Norway farmers, frustrated by their harvests being destroyed through snow, rain and moisture penetrating into their barns started constructing a secondary exterior wall structure. The assumption was that while water would penetrate the outer wall, it would have difficulty getting through the inner wall. What surprised them was that when they were only using a single wall constructed barn, the snow and rain would pass through the wall and easily get into their harvest. However with a secondary exterior wall the moisture would pass through the outer wall but not get to the inner wall. The barns were constructed of timber so the joints between timbers allowed air to pass freely through. Any rain or moisture that penetrated the outer wall was either heavy enough to drop between the cavity to ground level or small enough to adhere to the inner surface of the outer wall. These smaller moisture particles were then dried off by the free flowing air in the cavity. Hence the use of a back-ventilated cavity was born.

The essence of this construction method employed by the Norwegian farmers is that it accepts that you cannot keep water/moisture from penetrating the outer skin of a structure, but you can deal with it before it reaches the secondary barrier.

Up to this time, construction methods assumed that using a single-wall barrier design with a secondary gutter back-up system was sufficient to prevent moisture penetration into the interior of a building. However much of the single-wall barriers were using permeable materials such as brick, block, mortar or concrete. The discovery of the back-ventilated cavity led European architects and engineers to design their exterior walls with a ventilated cavity and this developed into what we now refer to as the Rainscreen Principle. Europe has been using the Rainscreen Principle almost exclusively as its primary method of construction for some 40-years. Throughout this time different cladding material manufacturers have developed their products to be used as a Rainscreen.

Rainscreen Principle construction methods were brought to the US market about 20-years ago and while it is currently a well developed method of construction on the East Coast and in the North West it is still in its infancy in the Southern States.

The essence of a true Rainscreen wall comprises of:

  • Stud wall construction.
  • Sheathing attached back to the studs.
  • An air-vapor barrier is applied over the sheathing.
  • Aluminum or other metal sub-construction comprising of girts and cladding supports attached back to the studs, to support the exterior cladding material.
  • Exterior rigid insulation which is installed over the air-vapor barrier and held in place by the sub-construction girts
  • The cladding supports should be designed to create the back-ventilated cavity between the exterior face of the rigid insulation and the interior surface of the cladding material.
  • The exterior cladding attached back to the cladding supports.

The advantage of using NeaCera® Terra-cotta Panels as a rainscreen is that NeaCera terra-cotta panels are impervious to water penetration, so the only moisture that will penetrate through the outer skin will be that which passes through the open-joints.