Air Barrier Performance and Life Cycle from Inception to Installation

Abstract

An air barrier system is the combination of interconnected materials, assemblies, sealed joints, and components of the building enclosure that control airflow between conditioned and unconditioned spaces or between spaces that are conditioned differently. For it to perform its intended function to control airflow across the building enclosure, the air barrier must be air impermeable, must be continuous, must maintain structural integrity, and must be durable in its installed and long-term application. When these performance requirements are met, a continuous air barrier will provide energy savings, comfort for the building occupants, durability, and a reduced environmental footprint. The first portion of this paper will describe the air barrier’s environmental benefits by comparing the “environmental cost” of an air barrier system throughout its life cycle assessment (LCA) with the “environmental benefits” due to building envelope airtightness during the building use phase (estimated through whole building energy simulations). The analysis of two air barrier systems shows that the environmental payback period is between a few months to a year and that the energy saved through airtightness over the operational phase of the building amounts to significant energy and CO2 emission credits. The second portion of this paper will discuss design- and construction-related items that are critical to air barrier and, ultimately, to whole building performance. Since the interface between the air barrier materials and adjacent systems (e.g., roofing, fenestration, waterproofing, penetrations, etc.) is oftentimes where whole building performance is most influenced, the designer must clearly illustrate the continuity of the air barrier across all interfaces, transitions, and penetrations. Examples of such details will be discussed.