A simple model is developed for the estimation of annual infiltration rates in single- family houses using indicators for both house tightness (air changes at 50 Pa) and site climate (the leakage-infiltration ratio). This technique is best suited to low-accuracy, large dataset problems where detailed data are not available. The method is similar to the method attributed to Kronvall and Persily (i.e. the K-P method), but is derived from a physical model, the LBL infiltration model. The estimation technique is developed assuming a typical, single-story dwelling; correction factors for common variations in building and environmental conditions are tabulated. A map of the leakage-infiltration ratio in the U.S. for the reference case is also presented.