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While the importance of air barrier systems in buildings has been understood for decades, it is only in the past decade or so that they have been given appropriate attention in the energy codes of most countries. While at least one country has had air barrier requirements in their codes since the mid-1980s, the “model energy codes” of others have largely ignored the issue until recently. Studies in the United States in the early 2000s that showed the potential for significant energy savings due to airtightness improvements in buildings were instrumental in getting air barriers incorporated into both the ASHRAE 90.1 standard and the International Energy Conservation Code (IECC), both of which form the basis for almost every energy code in the country.
As many in the buildings industry have discovered, getting air barriers into the energy codes was only the first step. Airtightness in buildings is an extremely complicated issue, as it spans so many aspects of both design and construction. If a designer specifies a maximum U-factor for a window system or a minimum R-value for wall insulation, the chances of installed systems varying significantly from those performance levels are relatively small. With air barriers, however, simply specifying a material with a certain air permeance is nowhere near sufficient to achieve that performance on the whole-building scale. The material needs to be properly integrated with all aspects of the enclosure, from below-grade waterproofing to roofing to fenestration. The overall impact on building airtightness now depends on the thoroughness of the detailing, the performance of the adjacent systems, and the quality of installation. This is in sharp contrast to thermal insulation, where the R-value is the R-value regardless of how the material is installed, and performance can be reliably calculated as opposed to requiring field testing.
To account for these concerns, many codes and building rating systems (such as Passive House) have started to include requirements for whole-building air leakage testing to confirm the effectiveness of the air barrier system. Again, this is a good first step, but the practical difficulties of air leakage testing are not widely understood. This paper reviews the development of air barrier requirements in model energy codes, including whole building testing, and discusses the practical limitations of current codes. The authors present strategies for both improving building airtightness through thorough design documentation and construction monitoring and for performing field testing to confirm execution and verify performance. We discuss how both designers and builders can meet these code requirements while considering the practical limitations of the construction process, from constructability to scheduling.