Continuous Insulation Rainscreen System from Knight Wall Systems
January 27, 2011
Knight Wall Systems’ CI-Girt is a “drop-in” commercial rainscreen system that simplifies installation of cladding over exterior foam insulation. The “CI” in CI-Girt emphasizes the importance of the system in supporting continuous insulation—insulation installed on a building exterior so that there are no penetrations other than fasteners and necessary openings. In contrast, insulation placed solely between the framing, particularly in steel-framed buildings, can lead to thermal bridging and moisture problems. CI-Girt is specified with all the component parts needed for the rainscreen, including rigid foam insulation (either XPS or polyisocyanurate) and Knight Wall Systems’ cladding options—thin brick, stucco, tile, metal, cement and composite panels, and Boston Valley Terra Cotta. These claddings hang on the same frame, so one building can have several different looks without altering the rainscreen frame or insulation.
Rainscreens on non-residential buildings typically use a metal framework that holds cladding away from the exterior weather barrier. That space between the cladding and the weather barrier supports ventilation of the cladding and drying of errant moisture. But in steel-framed buildings using continuous foam insulation, the clips that anchor the cladding’s framework provide a thermal bridge through the insulation to the building’s interior. A thermal short-circuit like this compromises the nominal R-value of the building shell and can lead to condensation on the building interior, potentially leading to mold. The problem is serious enough that continuous insulation is a standard requirement for steel-framed buildings under ASHRAE 90.1-2007.