There is no easy answer to the question, “Is a material a water-resistive barrier, an air barrier, or a vapor retarder?” Building science will tell you, “It depends.” The answer depends on the material properties, quality of the installation, and how the material and installation are used in a building.” The answer is further complicated by the range of terms used in building codes and construction standards to describe the various control layers within the building enclosure. For example, the International Building Code (IBC)1 and International Residential Code (IRC)2 use the terms “weather-resistant barriers ,” “water-resistive barriers,” “air barriers,” and “vapor retarders” (formerly called “vapor barriers”) to identify different types of control layers. The IBC and IRC do not use the term “thermal insulation”; instead, they refer to “thermal isolation,” “R-value” (thermal resistance), and “thermal transmittance” or “U-factor.” This paper aims to help readers understand how the various control layers in a building enclosure are defined and cut through some of the confusion surrounding the key concepts and requirements related to control layers.
Learning Objectives:
- Explain the purpose of control layers.
- Determine the purpose of each barrier layer.
- Show why and where the confusion comes in when talking about each barrier.
- Discover the steps to demystify the definitions of each term.
Continuing Education Credit:
1.0 AIA LU HSW 
Laverne Dalgleish
Executive Director, Air Barrier Association in America
Mr. Laverne Dalgleish is the Executive Director of the Air Barrier Association of America (ABAA) and the Rainscreen Association in North America (RAiNA). As such, he works to champion energy conservation in buildings while educating the building owners and designers about the benefits of energy conservation such as durability, comfort, reduced maintenance, reduced HVAC equipment costs and the positive impact on the environment. Mr. Dalgleish travels North America on a weekly basis to educate building owners and designers on the benefits of effective and working air barrier systems in buildings. This education mission includes working with standards development organizations, training and education groups, government policy departments, and quality assurance program developers for the construction industry. Mr. Dalgleish is the Secretariat of two ISO Committees, ISO TC61 SC10 Cellular Plastics and ISO TC163 SC3 Thermal Insulation Products. He is also Chair of the ULC Thermal Performance in the Building Environment Standards Committee. Mr. Dalgleish was the key developer of the ABAA Quality Assurance Program for the installation of air barrier systems in buildings. This program is based on ISO9000 and ISO 12576-2 but brings the ISO requirements together with practical applications for the air barrier industry.