Wood rainscreens have become a fairly common occurrence in contemporary design. It is important to understand that a rainscreen is distinct from traditional wood cladding or siding, as a rainscreen is an open joint system. This creates a pressure equalized system between the outside air and the air behind the screen itself such that the wood can be ventilated, but most importantly such that water will not wick itself into the building due to the pressure differential between inside and outside. Much of contemporary geometrically complex architecture also develops through open joint systems as well, such as the open corner joints in Frank Gehry’s Disney Concert Hall. This allows for tolerance in complex geometries, but it also means that we should pay some deference to new roofing technologies that allow these complex geometries to be sealed up as the primary line of defense against moisture. These open joint cladding systems then certainly give the aesthetic finish to the building, but it is also important to understand that this is not just an aesthetic covering, but this exterior finish system in turn protects the waterproof membrane so these two work together as a system.
However, wood rainscreens are most often seen in orthogonal geometries, though exceptions due exist such as the roof of the Savill Building (which provides a nice cross reference with the Gridshell Research Focus area). A great example of where the correlation between straight laths and complex geometries DOES NOT work can be seen in the decks of the Yokohama Terminal – here we have an elegant formal concept that is striated by the IPE decking, while incredibly crafted, these lines cut across the desired form. Probably fair to say in this case that having the IPE decking dictate the terminal’s form would be the tail wagging the dog, nonetheless this research group is going to explore the reciprocity between building form and cladding in straight segments. This research focus area in flexible rainscreens should then primarily be seen as finding the limits of bending of straight laths, and a parametric means to distribute these laths over a master surface. The trick here is understanding the geodesic curve, which I will cover under a separate post. To begin with over the next two weeks, this research group needs to do the following:
- Precedent study / image mining of wood rainscreens and importantly, the different types of wood used in rainscreens.
- Analog Material Studies of what you can do with straight basswood laths.
- Digital Studies using the “shortestpath” command in Rhino to understand how these geodesics work on surfaces.
- Getting into Grasshopper using the Geodesic component and using sliders to control the distribution of geodesics across lofted study surfaces (how much curvature can you apply this too until it fails??).
The quarter research goal is this:
- A GH definition that will develop the geodesic laths with a back-up structure, both of which can be developed as cut files for digital fabrication (whether the cut files happens within GH all depends).
- Curvature Analysis from a real-world test lath curved to the maximum, and applying this curvature analysis to a wall study (I will explain this later) as a means to understand the limits of bending of selected wood material.
- Scaled models and Full-Scale prototypes of a curved wood rainscreen.
To start, begin with the four bullets above.