The September 2016 issue of The Construction Specifier featured the article, “The Thick and Thin of Fluid-applied Air Barriers,” written by Scott Wolff, CSI, CDT, and Todd C. Skopic, CSI, CDT, LEED AP.
PROSOCO Inc.’s Paul Grahovac (building envelope codes, standards, and field support), Joelle Lattimer (strategic account manager), and Dave Pennington (building envelope group manager) contacted the magazine with concerns about the piece. These comments have been edited into the following response to the article:
The water-resistive barrier (WRB) and air barrier sections of U.S. codes do not specify thick- or thin-mil products. (The fact ARCOM lists thin-mil products shows they are indeed suitable for use.) Generally speaking, thick-mil manufacturers have not qualified their products under the International Code Council Evaluation Service (ICC-ES) Evaluation Report process, but many thin-mil manufacturers have done so. This circumstance led a prominent specifier to state during an Air Barrier Association of America (ABAA) conference call, “Do you know what jeopardy you place specifiers in when you do not have ICC-ES evaluation reports corresponding to your products?”
In the article, the authors write, “It is important to acknowledge all other ‘sides’ of the building enclosure ‘box’ similarly employ thicker membranes in the prevention of water and air infiltration.” They cite foundations covered with 60-mil (i.e. 1.5-mm [0.06-in.]) styrene butadiene styrene (SBS) self-adhered sheet waterproofing or single or two-ply fluid-applied waterproofing, along with roofing membranes being applied in larger thicknesses. However, it is important to note foundation products are subject to back-fill abrasion, and roofing products are subject to windborne abrasion.
Fundamental systems engineering principles require products meet the needs of their specific application. However, air barrier materials are not subject to abrasion. They are not going to get thinner over time. There is no evidence thick-mil air barrier products last longer than thin-mil ones.
Under the article’s “Differences in thickness” section, the authors list various ASTM standards on which they say maximum air water vapor permeance of fluid-applied air barriers (FAABs) is based. However, ASTM E2178, Standard Test Method for Air Permeance of Building Materials, and ASTM E2357, Standard Test Method for Determining Air Leakage of Air Barrier Assemblies, are air leakage tests. For vapor permeability, the standard of performance is established by ABAA with ASTM E96, Standard Test Methods for Water Vapor Transmission of Materials. ABAA has no requirement other than reporting the results.
The article also states “thin-film membranes’ application are inherently more difficult to control (to achieve correct wet/dry film thickness),” but this is not so. Common sense indicates thin coatings would be easier to control. While the piece states thick-film air barriers typically need only one application, thin-mil products are typically only one application on gypsum sheathing, and two for concrete masonry units (CMUs).
Under the section titled “Crack-bridging performance properties,” the authors write:
A standard commonly used by thick-film manufacturers is ASTM C836, Standard Specification for High-solids-content, Cold-liquid-applied Elastomeric Waterproofing Membrane for Use with Separate Wearing Course. Some thin-film manufacturers may state “crack-bridging,” but neglect to reference the specific standard to back up the claim. (Thicker membranes have more body and mass to span the cracks.)
ABAA accepts either the ASTM C1305, Standard Test Method for Crack-bridging Ability of Liquid-applied Waterproofing Membrane, crack-bridging test embedded in ASTM C836 or the ICC-ES Acceptance Criteria (AC) testing for coatings used as water-resistive barriers. When an attempt was made at ABAA to require exclusively ASTM C1305, evidence was provided that the National Concrete Masonry Association (NCMA) considered the 3.2-mm (1/8-in.) movement of ASTM C1305 to be indicative of a structural defect in the CMU wall—the effort was then dropped. Curiously, some thick-mil manufacturers specify if a crack is present and is of a moving nature prior to product application, the crack is to be pre-treated with a more robust material. Why this is so when the thick-mil products are promoted as crack-bridgers remains a mystery.
With respect to tensile and elongation properties, neither ABAA nor ICC-ES have testing requirements on these parameters. If buildings moved sufficiently to exercise the high elongation of thick-mil products, they would likely fall apart—unless the authors are saying their products prevent that?
Under the section “Single-source opportunities,” the authors write having a single-source supplier helps ensure compatibility. To us, the phrase “aces in their places” comes to mind. Why settle for a disadvantageous air barrier and flashing system (i.e. one that cannot be applied to damp substrates or immediately rained on) just so a warranty on the other, unrelated membranes on the project can be provided from the same company?
In fact, in some cases, a single-source situation may actually work against the owner—in terms of construction defects, insurance companies base their settlements largely on avoiding the cost of defense. Since there is only one insurance company to settle with, the single cost of defense covers all the products on the project. With multiple manufacturers, each insurance company chips in their cost of defense, and the owner is made whole much faster, more easily, and less expensively than going all the way to trial trying to get money out of a single insurance company.
