The paper briefly describes the AC pressurisation method of building airtightness measurement and the disadvantages of earlier analysis methods. A new analysis method is described, based on fitting a non-linear function of the unknowns to data. The function is derived from the differential equations of the system components. The new method performed well with simulated data. With real data, the method produced good estimates of the leakage flow rate at 4 Pa pressure loss, leakage length/area and enclosure flexing, but poor estimates of the leakage exponent. It is suspected that this problem was due to measurement errors.
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