Benefits of an Engineered Rainscreen Cladding System

"I'll just attach galvanized hat channels to the sheathing and fasten the panels to that! I can figure it out, it's not that difficult......"

The phrase that stirs in the bellies of facade consultants yet causes Euphoria in trial litigants through out the U.S.

Common to drained and back ventilated cladding system, few suppliers of rainscreen products in the U.S. offer a system-based solution, let alone one that is engineered and tested. Is this due to the infancy of European rainscreen products in our market, or that there is a shortage of skillsets available that would encourage better practices common to most other exterior facade materials?

In the glazing industry, it is expected that the material supplier engineer, fabricate and assemble the window or curtainwall product (either fully or partially). And numerous standards are available to assess the practical performance of the glazing products (from ASTM, AAMA and NFRC). Equally common in the metal panel industry, we typically find cladding systems that are engineered for windload, seismic conditions, and thermal movements AND are tested to high performance levels for air and water infiltration.

So why is it a common practice that suppliers limit the service that they offer for their products to a "panel-only" sale? Can we assume that the construction community in the U.S. prefers to innovate rather than use solutions tested and readily available? I think this practice has been borne out of necessity on the designers part as well as a shortage of information on "best-practices" for this industry. Fortunately, forces are under foot in the U.S. to develop national standards for rainscreen cladding testing that will establish minimum standards of performance, as well as various classification levels associated with the tested performance values of the rainscreen cladding products (a standard is currently available for pressure equalized systems, and a standard for drained and back ventilated claddings is due out by the end of 2009).

The next step in the evolution of rainscreen products in the U.S. market will be to encourage the use of skilled trades for the installation of these weatherproofing products. Unlike the residential construction market where general trade contractors commonly install siding products, the commercial construction market typcially looks to specialty subcontractors for the installation of exterior cladding products. But for some reason, the installation of rainscreen cladding materials often times follows a different course. Again, I think this can be attributed to a shortage of knowledge about what comprises a quality rainscreen cladding system and what is truly required to install a cladding product that will achieve a long and serviceable life (let alone the minimum standards of performance one can expect with rainscreen cladding systems).

Our next post will discuss the parameters available with rainscreen cladding systems and the performance opportunities that can be achieved by simple design solutions.