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66 SEPTEMBER 2016 COATINGSPROMAG.COM Never Again O n a s p l i t- leve l b u i ld i n g i n N o r t h Carolina, the fluid-applied (FA) air barrier started to peel away from the co n c rete m aso n r y u n i t (C M U ) a n d gypsum wall sheathing (GWS) within 24 hours of application. The Case of the Peeling Air Barrier By Robert F. Mimmo and Brian H. Neely, AIA, CDT, BECxP Gale Associates, Inc. I n the United States, air barriers have become an integral part of modern construction since the start of the 21st century. Since 2001, several states have implemented the requirement of a continuous air barrier within their building codes. With the introduction of a continuous air barrier in ASHR AE 90.1-2010 Energ y Standard for Buildings Except Low-Rise Residential Buildings and the 2012 International Energy Conservation Code, the adoption of air barriers is expanding. e driving forces behind this movement are to decrease energy costs, address the health and well-being of the build- ing's occupants, and increase facility durability through control of air infil- tration and exfiltration within the exterior building enclosure. Unfortunately, the applications don't always match the intentions… Air Barrier Background ere are three primary types of air barriers: fluid-applied (FA), self-ad- hered (SA), and spray polyurethane foam (SPF). Each of these has its own unique characteristics and properties. However, they all have the following basic principles in common: • Continuous • Able to withstand positive and negative wind, fan, and stack pressures enacted on a building • Capable of transferring the load to the structure • Durable and maintainable • Able to accommodate movement in the structure • Meet air permeability requirements of 0.004 CFM (0.0001 cm/min.) per square foot (0.09 m²) under pressure differential of 0.3 inches (7.6 mm) of water A ir bar r iers do not just stop uncontrol led air inf i ltration. Since air contains moisture, air bar r iers a lso help to avoid the deter ioration and mold caused by moisture condensing w ithin a wa l l assembly. Photos courtesy of Gale Associates, Inc Unfortunately, many installed air barriers fail after a short period of time.