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.