The following article appeared in the February 1999 edition of Energy Design Update, a technical newsletter published by Cutter Information Corporation.
ASTM Task Group to Write New Standards for Weather-Resistive Barriers
We have some good news…and some bad. The good news is that the American Society for Testing & Materials (ASTM) has formed a task group, under the able leadership of architect Tom Butt, to write new standards for “weather-resistive barriers.” The bad news is that the task might be compared to untying the Gordian knot and could take two or more years to yield meaningful results.
As things stand now, the three main types of weather-resistive barriers—building paper, house wrap, and asphalt-saturated organic felt—are tested and described under dozens of different performance and material standards. This makes it impossible for designers and product specifiers to compare key performance characteristics; strength (tear, tensile, and burst), water resistance, water vapor transmission, and air penetration.
“As an architect, I want test methods and criteria by which I can look at these various weather-resistive barriers, compare them, and select the one that’s most cost-effective for the job,” says Butt, who is president of Interactive Resources, Inc. (Richmond, California). He tells EDU that the committee’s first priority will be to collect in one place all of the standards that apply and then find out what committee members like and dislike about them. One weakness that’s common in most existing standards is that they fail to recognize how temperature and humidity can affect the performance of weather-resistive barriers.
Once the committee members have hashed through the existing standards, they will define performance criteria and try to achieve a consensus on test methods. Part of the difficulty in reaching such a consensus is that there are at least three different industries represented at the table: the paper industry (building paper), the plastics industry (house wrap), and the roofing industry (asphalt-saturated organic felt).
Another challenge will be to resolve the question of testing material properties versus system performance. At the committee’s last meeting, several members pointed out that the performance of weather-resistive barriers is highly dependent on installation techniques. How, for example, do you test a weather-resistive barrier for water resistance when it’s typically installed behind a weather-resistive finish material? Do you vary the test according to type of finish?
Yet another roadblock to establishing an effective new standard is the vested interest that suppliers have in emphasizing the strengths of their products and downplaying the weaknesses. Thus, the rules must be written so that producers cannot manipulate the tests.
“These various materials are being sold as weather-resistive barriers not because they are ideal for the purpose, but because they exist and offer some good characteristics that can be emphasized,” Butt says. “None were developed with the end use in mind. In fact, it’s widely believed—both inside the committee and out—that the ideal material is not even on the market, but could be developed.”
Should the committee come to a consensus on a new standard, the final challenge will be to get manufacturers to actually retest their products and publish product specifications based on the new standard. Experience has shown that a new standard may be widely ignored by suppliers (e.g., ASTM E1677-95, Standard Specification for an Air Retarder Material or System for Low-Rise Framed Building Walls) unless there’s a follow-on effort to have it incorporated in building codes.
Despite all the hurdles before him, Butt describes himself as optimistic. “We have all of the right players at the table,” he says. “And I think everyone feels that it’s a worthy cause.”
The next meeting of ASTM Task Group E06.55.07 (Weather Resistive Barriers) is slated for April 18-21 in Seattle, Washington. For information, contact Thomas Butt, Interactive Resources, Inc., 117 Park Place, Richmond, CA 94801. Tel: (510) 236-7435; Fax: (510) 232-5325; E-mail: tom.butt@intres.com.
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