States it is often assumed that commercial and institutional buildings are fairly airtight and that envelope air leakage does not have a significant impact on energy consumption and indoor air quality in these buildings. Furthermore, it is assumed that more recently constructed buildings are tighter than older buildings. Reports on an analysis of envelope airtightness data obtained by fan pressurisation testing from 139 commercial and institutional buildings around the world, assembled from the published literature. The buildings include office buildings, schools, retail buildings, industrial buildings and a number of other building types. Summarises them in a table. States the data show significant levels of air leakage in these buildings. Finds no correlations of airtightness with building age, size or construction. Taller buildings are shown to be tighter. Points out that the small number of buildings and the fact that they are not random samples of the building stock at large limits the generalisability of any conclusions.