{"id":18259,"date":"2016-08-26T10:00:16","date_gmt":"2016-08-26T14:00:16","guid":{"rendered":"http:\/\/www.constructionspecifier.com\/?p=18259"},"modified":"2017-02-07T15:11:47","modified_gmt":"2017-02-07T20:11:47","slug":"the-thick-and-thin-of-fluid-applied-air-barriers","status":"publish","type":"post","link":"https:\/\/www.constructionspecifier.com\/the-thick-and-thin-of-fluid-applied-air-barriers\/","title":{"rendered":"The thick and thin of fluid-applied air barriers"},"content":{"rendered":"
\"OLYMPUS
All images courtesy Henry Company<\/span><\/figcaption><\/figure>\n

by Scott Wolff, CSI, CDT, and Todd C. Skopic, CSI, CDT, LEED AP
\n<\/strong>The fluid-applied air barrier (FAAB) concept was originally a Canadian-developed technology from more than 40 years ago. Back in the early 1970s, the genesis was an adhesive combining air- and vapor-retarding characteristics\u2014eventually, this material would find its way into building codes.<\/p>\n

The earliest FAABs were heavy-bodied products with predictably thick wet film\/dry film applications. As it turns out, thicker membranes would have many advantages. Industry organizations such as ARCOM\u2019s MasterSpec<\/em> created the \u201cfluid-applied membrane air barriers\u2019 specification for these membranes with \u201cnot less than 40 mils dry film thickness (DFT),\u201d that is,
\n1 mm (0.04 in.).<\/p>\n

It is important to acknowledge all other \u2018sides\u2019 of the building enclosure \u2018box\u2019 similarly employ thicker membranes in the prevention of water and air infiltration. Foundations are commonly covered with 60-mil (i.e.<\/em> 1.5-mm [0.06-in.]) styrene butadiene styrene (SBS) self-adhered sheet waterproofing (e.g.<\/em> rubberized asphalt) or single or two-ply fluid-applied waterproofing. These are commonly in the 60 to 120 mils (i.e.<\/em> 3-mm [0.12-in.]) DFT range. Roofing membranes, such as single-ply membranes, are also applied in larger thicknesses\u2014typically in the 60 to 80-mil (i.e.<\/em> 2-mm [0.08-in.]) DFT range or higher.<\/p>\n

Enter the \u2018thin-film\u2019 era of air barriers. This phenomenon began approximately 15 years ago and was born out of the exterior insulation<\/em> and finish<\/em> systems (EIFS) industry. EIFS manufacturers provide single-sourced water-resistive barrier (WRB), insulation, and finished exterior wall assemblies. All may be well and good, but within the past 10 years, MasterSpec<\/em> eventually addressed this new class of FAAB with a new specification titled \u201cAir Barrier Coatings.\u201d<\/p>\n

In this specification, DFT values are listed at 14 and 17 mils (i.e.<\/em> 0.35 and 0.43 mm [0.014 and 0.017 in.]) for vapor-retarding and vapor-permeable \u2018coatings,\u2019 respectively. Absent in the air barrier coatings specification language for DFT are the words \u201cnot less than.\u201d Essentially, these \u2018coatings\u2019 can be even less than 14 mils.<\/p>\n

\"AB06
Thick-film FAAB installation over plywood sheathing. As an alternative to the sheet membrane detail strip over the plywood sheathing joints, an approved sealant can be also be used.<\/span><\/figcaption><\/figure>\n

In 2015, MasterSpec<\/em> decided to combine the two specifications into one. Gone is the \u201cAir Barrier Coatings\u201d title while the \u201cFluid-applied Membrane Air Barriers\u201d remains. This new version contains three sections in Part 2\u2212Products and Part 3\u2212Execution for different thicknesses:<\/p>\n