Stringent energy codes are making fully adhered air and water resistive barriers (AWBs) and continuous insulation (CI) common place for new building construction. Since AWBs require continuity to perform successfully, design professionals are paying more attention to specific detailing requirements. Mechanical penetrations, structural members and fenestration openings are obvious points for scrutiny. But what about cladding attachments, particularly through CI?
Several thermally efficient systems are marketed today to attach cladding through CI. The main types are clip and rail; low-conductivity girts; and furring with long screws. Each has a unique attachment method, with varying potential effects on air and water tightness and the overall thermal performance.
Recently Carlisle Coatings & Waterproofing (CCW) partnered with Knight Wall Systems (KWS) which offers several engineered systems for attaching cladding through CI. KWS’s HCI system was chosen for evaluation because it is the company’s most thermally efficient system for cladding attachment over rigid foam CI. KWS HCI is a “furring with long screws” type system. The team was interested in evaluating the water tightness of the assembly, since this type of system does not allow any detailing of fastener penetrations made through the AWB membrane (if the AWB is under the CI).
The team contracted with York, PA-based Intertek to test the water tightness of a wall assembly built with CCW Barritech VP as the AWB, Hunter XCI Foil (Class A) polyiso as the CI, and an open-joint cladding by Swiss Pearl which was attached through the CI and AWB with the KWS HCI system. To evaluate water tightness, the wall assembly would be punished with the toughest version of the wind-driven rain test, ASTM E 331. Go here to see the test results.