The fan pressurization method is a common practice in many countries for measuring the
air leakage of houses. The test results are sensitive to uncertainties in the measured
pressures and airflows. In particular, changing wind conditions during a test result in
some pressure stations having more or less uncertainty than others. Usually, it is
necessary to fit the measured data to the power-law equation. Using the ordinary least
square (OLS) fitting method, the pressure exponent and flow coefficient can be
determined, and the reported data at high pressures can be extrapolated to small pressures
where natural infiltration occurs. However, this fitting method neglects the existing of the
uncertainty of these measurements, which may lead to errors in the prediction of flows at
low pressures and therefore to unreliable input data for energy simulations. The weighted
line of organic correlation (WLOC) takes the uncertainty at each pressure station into
account and minimizes the fitting residuals for both pressure and flow. This paper shows
the results of a statistical analysis of an extensive data set of over 7.400 fan pressurization
test of six houses in 109 different leakage configurations. It was found that in over 90 %
of the analyzed cases, WLOC enables a more reliable prediction of pressure exponent and
flow coefficient at low pressure compared to OLS and appears to be a better fitting
technique.