In many countries, the fan pressurization method is the most frequently chosen approach for measuring the air
leakage of houses. The measurements are usually performed at pressures that far exceed pressures to which
buildings are exposed to under normal conditions. A fit of these tests to the power-law formulation allows an
extrapolation to data points outside the measured pressure range. With the Ordinary Least Square (OLS) fitting
method, the pressure exponent and flow coefficient can be determined. However, the measurement results are
highly sensitive to uncertainties induced by external factors like changing wind conditions during the tests,
which is neglected by OLS. This may lead to errors in the prediction of flows at lower pressures. The Weighted
Line of Organic Correlation (WLOC) is an alternative approach and takes measurement uncertainty into account.
In this paper, a statistical analysis of an extensive data set of pressurization measurements has been performed.
Both regression techniques have been compared for almost 7500 fan pressurization measurements of six houses
in 109 different house leak configurations. The variability in predicting pressure exponent and flow coefficient
for both WLOC and OLS regression was analyzed using probability density functions. It was found that the
Weighted Line of Organic Correlation significantly decreases the uncertainty in predicting pressure exponent,
flow coefficient, and other low-pressure air leakage metrics compared to the Ordinary Least Square fitting. The
authors highly recommend the implementation of WLOC in current measurement standards and test equipment