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In 1998, NIST published a review of commercial and institutional building airtightness data that found significant levels of air leakage and debunked the "myth" of the airtight commercial building (Persily, 1998). Since then, NIST has expanded and maintained a database of whole building envelope leakage measurements of U.S. commercial and institutional buildings. In addition to building leakage values collected from research publications, low-energy building programs and private pressurization testing firms, the database includes basic building characteristics such as year built, building type, floor area, number of storeys, location, and wall construction type for many of the buildings. The purposes of the database are to support the design and construction of low-energy buildings, to establish default values for building simulation, to estimate the energy savings potential of airtightness requirements in standards and codes, and to identify opportunities for additional improvements in building airtightness performance.
The U.S. commercial building envelope leakage database contains data for almost 400 buildings including about 70 constructed in the past decade. The average air leakage for the buildings is 20% tighter than the average for the 228 buildings included in a similar 2011 analysis. The data were analysed to determine the factors that impact airtightness such as building type and height. Recent additions to the database include numerous buildings constructed to meet the specifications of sustainable building programs such as the U.S. Green Building Council's LEED rating system, as well as buildings designed and constructed with air barriers. The analysis found that the 79 buildings with an air barrier had an average air leakage almost 70% less than the average for the 290 buildings not specified as having an air barrier thus demonstrating the critical need to design and construct commercial buildings with an air barrier to support sustainable building design.