A new ASTM International standard will describe in detail the design and specification process for water vapor transmission properties of water-resistive barriers and air barriers(WRB/AB) in building construction. ASTM’s performance of buildings committee (E06) developed the new standard, which will soon be published as E3127.
ASTM International member Danko Davidovic says that the new standard will explain how WRB/AB systems perform in different wall and roof assemblies in various climates when the moisture migration by water vapor diffusion is taken into consideration. The standard reflects the current best building science practices with regards to how water vapor transmission properties of WRB/AB impact moisture transport and moisture management in wall and roof assemblies. It also acknowledges the dynamic behavior of WRB/AB and describes the benefits of expanding testing requirements to several temperature and relative humidity levels in order to better describe the behavior of WRB/AB in service.
“The new standard is focused on the most relevant factors affecting performance of WRB/AB, best practices to test, report, and specify water vapor transmission characteristics without going into in-depth analysis and not using overwhelming technical language,” says Davidovic.
Davidovic envisions several ways the new standard will be used:
- Manufacturers can use the standard as a resource to educate themselves about the actual performance of WRB/AB products and use it as a guide to improve the product characteristics of WRB/AB and make it more suitable for certain climates, and building envelope types;
- Regulatory agencies can us the guide to improve requirements for WRB/AB materials and systems in current building codes;
- Architects, designers, and engineers will use the standard to better calibrate requirements and specify water vapor transmission properties in design documents; and,
- The new standard could be a supplemental educational tool in engineering curriculums pertinent to building envelopes in colleges, as well as in industry trade training programs.
This effort relates to the United Nations Sustainable Development Goal #9 on industry, innovation, and infrastructure.
“Recommendations and guidelines provided in the new standard should establish a solid framework for design of more durable wall and roof assemblies that will provide healthier indoor environments for humans and reduce potential risk for moisture-related damage in building envelopes,” says Davidovic. “This could lead to longer lifespan of buildings and reduction in construction waste, which also may result in more sustainable and resilient buildings, advocating construction practices that will support such intent."
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