CoatingsPro Magazine

MAY 2018

CoatingsPro offers an in-depth look at coatings based on case studies, successful business operation, new products, industry news, and the safe and profitable use of coatings and equipment.

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Page 68 of 92

68 MAY 2018 COATINGSPROMAG.COM Science Behind It W hat started out as an extensive value engineering (VE) effort on a recent mixed- use multifamily project, the Leadership in Energy and Environmental Design (LEED) Platinum Certified Keauhou Lane project in Honolulu, Hawaii, quickly became a study in exterior envelope assemblies. In an effort to reduce costs from the exterior envelope system that had been carried on the project since its incep- tion, the project's general contractor was proposing to revise the entire exterior assembly. It was to go from a metal panel and cementitious panel rain screen assembly to an exterior insulation finishing system (EIFS). History of EIFS W hen EIFS assemblies started to make their way to market, many of the assemblies were presented as barrier, or face-sealed, systems that did not have a full drainage assembly behind them. is meant that any water that was able to make its way behind a poorly caulked back-wrapped condition, a fairly common occurrence, would not be able to make its way out of the structure. As such, the late 1980s saw a good amount of leak claims and EIFS-related litigation, which in turn gave EIFS as a product a bit of a black eye. e counter argument, of course, was that it wasn't a failure of the product but more specifically a failure of the labor and the installation. (Remember that poorly caulked back-wrap condition? is is where it rears its ugly head.) In recognition of this reality (i.e., even with the best tradesmen on your project, all joints and installations cannot be expected to be perfectly sealed), the EIFS industry and the building codes finally started to change, and they now require exterior exposed assemblies to be drainable assemblies, allowing any trapped water a way out of the envelope assembly. Current Systems Because of the historical issues of EIFS, we needed to agree on a fully drainable system prior to launching into project detailing. Furthering this argument was an understanding of the climate that this particular project was being built in: the hot and humid climate of Honolulu, Hawaii. W hile it is true that some of the older EIFS installations did not reveal major issues in their life cycles in hot and dry climates, it needs to be understood that those climates would allow higher rates of drying due to their climate. Inasmuch, envelope intrusion and moisture damage is typically as simple as understanding the flow rates of the moisture that are allowed to get into the envelope assembly. In short, if the water is not able to dry out and evaporate, which may be the case in dry, hot climates, it needs a path that will allow the water back out of the building. In Honolulu's humid climate with annual rainfall typically exceeding 20 inches (50.8 cm) and humidity that can hang around 90+ percent from August to November, there is little hope that the climate will be your friend and dry out any water in your building envelope. Current drainable EIFS assemblies tend to be fairly similar, and they usually employ a barrier assembly at the exterior over a rigid insulation over a drain- age cavity protected by a weather barrier over sheathing. is combination of assemblies allows any trapped moisture that does work its way into the assembly to run back out through weeps at the base of the assembly. For instance, at Keauhou Lane, we utilized a propri- etary manufacturer's air/water barrier that was applied continuously over the sheathing. In applying the continuous insulation for the system, the product required vertically notched adhesive beads to be employed, which create verti- cal paths of travel for any moisture to make its way to the base of the assembly and ultimately out. W hether utilizing vertical trowel-notched adhesive channels, textured building wraps, or other approaches for drainage, the constant in all approved exterior EIFS assemblies is a drainage plane behind the initial barrier assembly that allows water to escape your envelope once it finds a way in. Mission Critical While the concept of a fully drainable EIFS assembly is far from rocket science, it is very much mission critical. With a well-de- signed and implemented drainable assembly, EIFS can be a viable envelope option for any climate as long as the details and science of the specific project are understood by all. CP Drainable EIFS Assemblies By Phil Camp, AIA, LEED A.P., WELL A.P., Principal at hi.arch.y llp

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