Environmental Benefits of Continuous Air Barriers: Energy and CO_2 Emissions Reduction Due to Building Envelope Airtightness

摘要

The building envelope makes a significant contribution to a building's energy performance, and its energy efficiency is critical because the envelope is expected to perform for the life of the building. This paper describes the environmental benefits of continuous air barriers for air leakage control. The full environmental impact of a building material can be estimated through life cycle-based environmental tools, such as life-cycle assessment (LCA) and environmental product declarations (EPDs). LCA provides information on the entire life cycle of the product, from raw materials extraction and processing, transportation, manufacture, installation, and use through disposal, recycling, or reuse. The LCA of building products often addresses only the upstream stages of the building life cycle, before the construction and building use phases begin ("cradle to gate"). The cradle-to-gate LCA approach does not capture the product potential contribution to energy savings during the building use phase. This paper provides an assessment of environmental benefits of air barrier systems, to include the building use phase. The analysis compares the environmental cost (expressed as energy use and CO_2 emissions) for the production, installation, and disposal of the weather barrier system from LCA, with the environmental benefits resulting from energy savings and CO_2 emissions reduction during the building's operational phase (attributed to building envelope airtightness). Because LCA is system specific, the calculations are based on LCAs of two categories of air barriers: fluid-applied and building wrap systems. The analysis shows that the environmental payback period for these systems is between a few months to a year, much shorter than the building envelope service life. This indicates that a properly installed weather barrier system able to provide an airtight building envelope would result in net impact reductions in the building's environmental footprint relative to a baseline option without such a system.