European Rainscreen Systems

The rainscreen principle is not new, nor is the idea of rainscreen applied to wall design. For centuries in Norway, the rainscreen idea was intuitively used, without any scientific, systematic foundation. They utilized drained and back-ventilated claddings with both closed and open joints. On buildings with timber claddings, closed joints were adopted, and openings at both the top and bottom of the cladding allowed for drainage and evaporation of any penetrating rainwater. The Norwegians titled this approach the “open-jointed barn technique,” since originally it was used in conjunction with the construction of barns. [1]

It wasn’t until the 1940’s that research organizations began delving further into the principles behind rainscreen and recognizing the superiority of a rainscreen system: “It is clearly unwise to allow walls, whether brick or porous cement, to be exposed to heavy rain. They absorb water like blotting paper and it would therefore be a great step forward if an outer, water repelling screen could be fitted to brick walls, with satisfactory characteristics from the point of view of appearance, mechanical strength, and cost. This screen could be applied so that water vapor coming from within is automatically removed by ventilation of the space between the wall and the screen.” [2]

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 utilize 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 1940’s. It was quickly recognized that the principles involved in rainscreen cladding were 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 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 vapor that finds its way into the space between the wall and the cladding

History of rainscreen siding – 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 utilize drained and back-ventilated cladding with joints that were both closed and open. The first buildings to have this type of rainscreen 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 recognized that the principles involved in rainscreen cladding were vastly superior to anything else in use at the time. That still holds true today. Green Aspects of Rainscreen Siding – Rainscreen siding is considered a green building practice for two reasons. Utilizing a well-designed rainscreen vastly extends the life of your siding and minimizes thermal transfer.

By incorporating the rainscreen principle into building design, siding will last considerably longer because moisture will never be trapped between your exterior cladding and exterior wall envelope. A longer life for your siding equates to less material consumption due to material replacement.

Rainscreen systems also minimize thermal transfer by creating an air cavity behind the siding. This keeps the heat generated by sunlight on the outside of your house not allowing the heat to directly transfer inside -ultimately significantly reducing energy consumption and cooling costs.

References:

1. Anderson, J.M. & Gill, J.R. (1988). Rainscreen Cladding: A Guide to Design Principles and Practice. Butterworth-Heinemann.

2. Johansson, C.H. (1946). The influence of moisture on the heat conductance for bricks.