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

Abstract

Part 1 of this paper examines the uncertainties (errors) inherent in the determination of the low-pressure leakage of a building envelope. Current procedures use high-pressure data (typically 50 Pa) as a measure of the infiltration potential of an envelope. In reality, infiltration occurs at much lower pressures (typically 4 Pa). As a consequence, large uncertainties are inherent in the current procedures. It is shown that a technique for direct measurement of Q₄ could reduce the uncertainty by a factor of three or more. One of the keys to such a measurement is to consecutively measure Dp with and without an imposed flow in a short time. In Part 2 of this paper, a technique is described that enables such measurements to be made.