In 1998, Persily 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. This paper updates the earlier analysis for the United States by including data from over 100 additional buildings. The average airtightness of 28.4 m3/hm2 at 75 Pa is essentially the same as reported by Persily in 1998. This average airtightness is in the same range as that reported for typical U.S. houses and is also similar to averages reported for commercial buildings built in the United Kingdom prior to recent airtightness regulations. Additionally, the trend of taller buildings being tighter and the lack of correlation between year of construction and building air leakage observed are consistent with the earlier report. This new analysis also found a trend (with considerable scatter) towards tighter buildings in colder climates. Although this study more than doubles the number of buildings in the air leakage database, any conclusions from this analysis are still limited by the number of buildings and lack of random sampling.