Building envelope airtightness is important for residential energy use, occupant health and comfort. Weanalyzed the air leakage measurements of 134,000 single-family detached homes in US, using normalizedleakage (NL) as the metric. Weatherization assistance programs (WAPs) and residential energy efficiencyprograms contributed most of the data. We performed regression analyses to examine the relationshipbetween NL and various house characteristics. Explanatory variables that are correlated with NL includeyear built, climate zone, floor area, house height, and whether homes participated in WAPs or if theyare energy efficiency rated homes. Foundation type and whether ducts are located outside or inside theconditioned space are also found to be useful parameters for predicting NL. We developed a regressionmodel that explains approximately 68% of the observed variability across US homes. Of these variablesconsidered, year built and climate zone are the two that have the largest influence on NL. The regressionmodel can be used to predict air leakage values for individual homes, and distributions for groups ofhomes, based on their characteristics. Using RECS 2009 data, the regression model predicts 90% of UShouses have NL between 0.22 and 1.95, with a median of 0.67.