1.1 本文件涵盖了指定高等级防水屏障和空气屏障（WRB/AB）的水蒸气传输（WVT）特性的指南，这些屏障通常安装在北美建筑结构构件和构成建筑围护结构外侧的覆层之间。 1.2 本指南适用于所有类型的防水屏障和空气屏障产品，包括多功能产品，无论制造工艺、材料类型或安装技术如何。 1.3 本指南提供了规定和报告WRB/AB水蒸气传输特性的一般规定，该特性是根据这些产品在建筑围护结构内通常经历的使用条件，通过标准化测试方法确定的。 1.4 针对特定使用条件优化WRB/AB的水蒸气传输特性超出了本指南的范围。 具体使用条件应考虑室内和室外气候、覆层类型、覆层材料的储湿能力、墙壁和屋顶组件的隔热措施、空气流动和蒸汽扩散控制策略的变化。 1.5 本指南不涉及WRB/AB与其他墙壁和屋顶组件的正确安装和集成。 1.6 以英寸磅为单位的数值应单独视为标准。在正文中，括号中所示的国际单位制仅供参考。每个系统中规定的数值并不完全相等；因此，每个系统应独立使用。将两个系统的值合并可能导致不符合标准。但是，可以使用适当的转换因子在系统之间转换导出的结果（请参见 表1 ). 1.7 本标准并不旨在解决与其使用相关的所有安全问题（如有）。本标准的使用者有责任在使用前制定适当的安全、健康和环境实践，并确定监管限制的适用性。 1.8 本国际标准是根据世界贸易组织技术性贸易壁垒委员会发布的《关于制定国际标准、指南和建议的原则的决定》中确立的国际公认的标准化原则制定的。 ====意义和用途====== 4.1 随着建筑行业向基于性能的设计转变，与预期使用条件一致的材料性能规范对设计过程至关重要。 在规定水蒸气传输特性时，重要的是要确定在与预期使用条件相关的测试条件下测量的WRB/AB产品的水蒸气传输性能。本指南提供了一个基于性能的框架，用于表征WRB/AB的水蒸气传输特性。 4.2 在指定WRB/AB时，水蒸气渗透性是一个重要的属性，需要考虑正确的湿度管理以及使用中的墙壁和屋顶组件的功能。在北美，传统上按照测试方法测试防水和隔气材料的水蒸气传输性能 E96/E96M 。本指南采用ASTM E96/E96M 试验方法作为WRB/AB水蒸气传输特性的主要信息来源，除非设计专业人员另有指示。 4.3 大多数标准测试方法都依赖于一组有限的稳态测试条件来评估材料的水蒸气传输特性。用于测量和报告WRB/AB水蒸气传输值的测试条件应尽可能接近被测材料的使用条件（即，应涵盖产品安装在墙壁和屋顶组件中时将经历的温度和相对湿度条件范围）。当测试使用中预期的温度和相对湿度范围时，许多WRB/AB材料的水蒸气渗透性可能会变化超过一个数量级。因此，在为特定项目指定材料或组件设计时，应使用或评估材料最有可能在使用中经历的整个环境条件下的WVT特性。

1.1 This document covers guidelines for specifying water vapor transmission (WVT) properties for above-grade water-resistive barriers and air barriers (WRB/AB), typically installed between building structural components and cladding that compose the exterior side of building envelopes in North America. 1.2 This guide applies to all types of water-resistive barrier and air barrier products, including multifunctional products, regardless of the manufacturing process, type of material, or installation technique. 1.3 This guide provides general provisions for specifying and reporting the water vapor transmission properties of WRB/AB determined by standardized test methods, in accordance with in-service conditions these products typically experience within building envelopes. 1.4 It is beyond the scope of this guide to optimize the water vapor transmission characteristics of WRB/AB for specific conditions of use. The specific conditions of use should account for variations in indoor and outdoor climates, cladding type, moisture storage capacity of cladding materials, thermal insulating measures for wall and roof assemblies, air movement, and vapor diffusion control strategies. 1.5 This guide does not address proper installation and integration of WRB/AB with other wall and roof components. 1.6 The values stated in inch-pound units are to be regarded separately as standard. Within the text, the SI units shown in parentheses are provided for information only. The values stated in each system are not exact equivalents; therefore, each system shall be used independently. Combining values from two systems may result in non-conformance with the standard. However, derived results can be converted between systems using appropriate conversion factors (see Table 1 ). 1.7 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. 1.8 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee. ====== Significance And Use ====== 4.1 As the building industry shifts towards performance-based design, specification of material properties consistent with anticipated in-service conditions becomes paramount to the design process. When specifying water vapor transmission properties, it is important to identify water vapor transmission properties for WRB/AB products that are measured under test conditions relevant to anticipated in-service conditions. This guide provides a performance-based framework for characterizing the water vapor transmission properties of WRB/AB. 4.2 When specifying WRB/AB, water vapor permeance is an important attribute to consider for proper moisture management and functioning of wall and roof assemblies in service. In North America, water vapor transmission properties of water-resistive and air barrier materials are traditionally tested in accordance with Test Methods E96/E96M . This guide adopts the ASTM E96/E96M test methods as a primary source of information for water vapor transmission properties of WRB/AB unless otherwise instructed by the design professional. 4.3 Most standard test methods rely on a limited set of steady-state testing conditions for evaluating the water vapor transmission properties of materials. Test conditions used to measure and report water vapor transmission values of WRB/AB should represent the in-service conditions of the tested material as closely as possible (that is, should cover the range of temperature and relative humidity conditions the products will experience when installed in wall and roof assemblies). The water vapor permeance of many WRB/AB materials can vary by more than an order of magnitude when tested for ranges of temperatures and relative humidity expected in service. For this reason, WVT properties over the full range of environmental conditions that the material will most likely experience in service should be used or evaluated when specifying a material or assembly design for a specific project.