Norway is the place where rainscreen cladding had its birth. It was not a scientific breakthrough, however, but more a gradual discovery that happened centuries ago in a largely intuitive way. Norwegian builders, probably through trial and error, found a way to utilise drained and back-ventilated cladding with joints that were both closed and open.
The first buildings to have this type of cladding were large barns. This is why they called it “the open-jointed barn technique.” The timber cladding had closed joints with opening at the top and at the bottom of the timber to allow for water drainage, and also for the evaporation of any rain moisture that managed to penetrate inside.
Scientific research of the underlying principles of a rainscreen didn’t start until as late as the 1940s. It was quickly recognised that the principles involved in rainscreen cladding was vastly superior to anything else in use at the time. That still holds true today.
The early research concluded that it is unwise to allow walls made of brick or cement to be exposed to rain over a long period of time without having anything to prevent the porous nature of the materials from absorbing water in a way that is similar to blotting paper.
The idea of fitting an outer screen wall to porous brick and cement walls that could repel rainwater was adopted. It was also easy to make this screen aesthetically pleasing at the same time. Just because its primary purpose is to serve as a rainscreen, there is no reason why it can’t look good too.
The outer screen also needs to have strength qualities and it needs to have an acceptably low cost. The design also needs to be such that it can, through proper ventilation, remove any water vapour that finds its way into the space between the wall and the cladding.
The Alcoa building in Pittsburgh, Pennsylvania was one of the first very large buildings to utilise modern rainscreen cladding. The 30-story building was built with large baffled aluminium panels. The baffling provided resistance to penetration from water and the ventilation to dry and water moisture was provided in the airspace between the cladding and the main wall.
In the early 1960s the Norwegian Building Research Institute published the idea of equalising the air pressure between the screen and the wall with the air pressure on the outside. This has the effect of preventing water penetrating into the wall. The rainscreen prevents the actual wall becoming excessively wet.
The terms “rainscreen principle” and “open rainscreen” were first used in 1963 by the National Research Council of Canada. Research continued through the 1960s and 1970s with refinements being made principally in Canada and in Europe.
By the 1980s the principles of rainscreen cladding was well understood. Its use has proliferated, especially in Europe, and experimentation with various different materials is ongoing. Today, the potential problems that may arise through the effects of global warming is now being taken into consideration in building techniques and industry standards regarding rainscreen systems.
Source by David A Robinson
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