This paper proposes a new extended power law (EPL) of air infiltration in buildings as an alternative in certain cases to the widely used power law (PL) and quadratic law (QL). Specifics: it separates the airflow rates in laminar and turbulent components; improves the estimation of the leakage area; new evaluation of the airflow rate at low pressure differences. In various numerical comparisons several advantages of EPL are revealed and we appreciate that will raise interest and adoption by the software platforms that evaluate the airflow in buildings. Based on the measurement data (MD) of the Passive House Politehnica from Bucharest (Romania), EPL is validated and compared with other laws of infiltration. Four statistical indicators (PCC, RMSE, MBE and MAE) show that EPL has the best fit to MD. A generalized function of air leakage is developed and may serve in certain cases for a higher level of processing the MD for improved evaluations. An inverse problem approach finds the leakage area of the cracks in linear-perimetral and in circular compact distributions respectively. They are alternative to the consecrated notions ELA and EqLA. The leakage areas are estimated to be from 5 cm(2) (the case of LFCorrLA(1*) at pressurization in circular-compact formulation) up to 2085.7 cm(2) (the case of LFCorrLA at depressurization in linear-perimetral formulation). Among the surveyed leakage areas we appreciate that CorrLA offered the most realistic result. Through linear extrapolation of the laws of infiltration at low pressure difference EPL is compared with PL and QL and the differences are discussed. (C) 2017 Elsevier B.V. All rights reserved.