Determining the adventitious leakage of buildings at low pressure. Part 1. : uncertainties

The uncertainties inherent in the determination of the low-pressure leakage of building envelope are examined in the first part of that paper. High pressure data (50 Pa) is a procedure currently used as a measure of the infiltration potential of an envelope. But in reality infiltration occurs at much lower pressures (4 Pa) so large uncertainties are inherent in the current procedures. A technique for direct measurement of Q4 could reduce the uncertainty by a factor of three or more.