by Erik Missio | February 7, 2017 3:08 pm
The September 2016 issue of The Construction Specifier featured the article, “The Thick and Thin of Fluid-applied Air Barriers,[1]” 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.
The letter-writers continue:
While the article discusses potential problems with detailing, it is important to consider a thick-mil manufacturer’s presentation to the Building Enclosure Technology and Environment Council (BETEC) of the National Institute of Building Sciences (NIBS) emphasized the importance of field inspection to avoid sagging of thick-mil materials.
In their article, the authors write:
It is an established fact the thinner a membrane is, the more difficult it is to achieve a complete and uninterrupted film during application. This is based on the marked variations in substrate porosity of exterior gypsum sheathing, concrete, concrete masonry units, etc.
It is important to note this refers to thick-bodied products that lay on top of the surface. They must be applied at a thick millage to ensure membrane integrity. Thin-mil products absorb and fit themselves into the substrate, thus assuring a continuous membrane. That is why thin- mil products have been successfully tested on CMU to demonstrate air barrier performance.
Under the section, “Testing specifics,” the authors write:
Thin-film FAAB performance standards are tested at X mils. However, the specifications may require Y thickness, which is often two to three times that ‘X.’ This leads to the question of what those performance characteristics are at Y thickness.
We occasionally see specs we believe to be oversights, which call for thin-mil products to be applied at thick-mil thicknesses despite the literature of the thin-mil product calling for a thin-mil application. In those instances, we suggest the spec be revised.
The article included a photo showing a sheathing manufacturer’s logo visible through the coating. It is important to note when this occurs, it may simply be a complex interaction of:
In such cases, the coating manufacturer can help sort out these issues and ensure a performing application takes place.
The authors also mention racking forces. It is important to note many thin-mil products meet demanding racking tests imposed by ICC-ES—tests many thick-mil manufacturers have not performed.
Under “Durability and exposure,” the authors write:
Some building envelope consultants have been concerned with the influx of newcomers in the FAAB market, requiring them to comply with various ASTM test procedures. In some cases, they have tested fluid-applied air barriers to ASTM D471, Standard Test Method for Rubber Property Effect of Liquids. This test is intended for rubber ([EPDM]) pond liners, not FAAB.
While our company does not test under ASTM D471, we note the authors emphasize the importance of ASTM C836, which, as mentioned, relates to “cold-liquid-applied elastomeric waterproofing membrane for use with separate wearing course,” and was not intended for FAABs.
Finally, the article closes with some discussion of ASTM Committee E06−Performance of Buildings’s Work Group WK50742, which is writing a new standard, Standard Practice for Assessing the Durability of Fluid-applied Air and Water-resistive Barriers. In our opinion, it is important the ASTM process not be used to perpetuate products with physical properties—such as high elongation—that happen to be features of long-marketed and long-specified products, but do not impact real-world performance. Further, the ASTM process must not impede the introduction and market viability of sound product innovations. As the authors say, “Of course, in any area of building science, newer technologies are not to be ignored, and should be heralded.”
As thin-mil products (especially those marketed with fluid-applied flashing that replaces peel-and-stick and provide project-specific detailing) gain market share, we expect to see continued use of ‘durability’ (there is no abrasion in this application), ‘crack-bridging’ (despite structural defects and thick-mil products requiring pre-treatment of cracks), and ‘high elongation’ (patterns with structural failure) asserted against them. As an old salesman once said, “You have to sell what’s on the truck.” Perhaps some product innovation would be a better course.
We shared the letter with the original article’s authors, who have replied with the following:
Thanks for passing along these comments. Some of the discussion in the letter—such as the relevance of ICC code-compliance of FAABs—deals with topics never referenced in our article. However, I do take particular issue with the explanation that being able to see sheathing logos flashing through thin films is a result of “the logo’s pigment stability,” along with the statements that “substrate absorbency doesn’t matter” and “building up the FAAB” does nothing more than “increase costs.” These points simply do not reflect what we are seeing in the field.
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