June 5, 2020

Open-joint cladding systems allow more water and air to enter behind the cladding than non open-joint cladding systems do. Turns out that open-joint cladding systems outperform non open-joint cladding systems BECAUSE they allow more air behind them. Yes, the drying potential of the open-joint cladding system is an order of magnitude or more greater than non open-joint cladding systems. Additionally, open-joint cladding systems allow more drying from the wall assembly out than non-open joint cladding systems. Win-win!

Now, this will blow your mind. Smaller spaces behind the cladding outperform larger spaces because the pressure equalization is more equal between the face of the cladding and the open joint behind the cladding in a smaller space behind the cladding than a larger space behind the cladding. Since air is compressible and fluctuates very rapidly, the smaller space can "keep up with" the outside space than the larger space can. You want the pressure equalization because that keeps more rain out.

Funny thing is with an open joint, you might see behind the cladding, which means the sun can see it too. So some kind of UV protection needs to cover the sheathing and exterior insulation. Don't have a 50-year cladding with a 10-year life span because of UV! Same with water control and air-control layers.

Now, this same technology is used in the 2-stage joints of vinyl and aluminum extruded windows where you have both an inner seal and an outer seal. This is differently than wood windows. These traditionally rely on a face seal. But that is changing! Eastern bloc countries are now using the 2-stage technology.

So, open-joint cladding systems with drainage and back ventilation are a magnificent way to build a wall assembly.

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