Unintended Infiltration in buildings is responsible for a significant portion of the global housing stock energy demand. Today, the fan pressurization method, also known as blower-door test, is the most frequently used measurement method to evaluate the airtightness of buildings and determining the total air change rate of a building or a building element. However, the localization and quantification of single leaks in the building envelope remain difficult and time-consuming. In this paper, an acoustic method is introduced to estimate the leakage size of single leaks in buildings. Sound transmission measurements and measurements of airflow have been conducted in a laboratory test apparatus. The objective of this investigation is to compare acoustic measurements with airflow measurements of leaks under the same boundary conditions. The test apparatus consists of two chambers, which are separated by a test wall. This test wall represents a single characteristic air leakage path in the building envelope. Various types of wall structures with different slit geometries, wall thicknesses and insulation materials have been investigated. The acoustic measurements have been performed with a sound source placed in one chamber and ultrasonic microphones located in both chambers. The results of the acoustic measurements were compared to airflows through the test wall measured using a flow nozzle to provide estimates of the uncertainty in the acoustic approach.

Today, the fan pressurization method is the most frequently used method to evaluate a building's airtightness. However, the localization and quantification of leaks remain difficult. In this paper, an acoustic method is introduced to estimate the leakage size of single leaks. Acoustic and airflow measurements were conducted and compared in laboratory tests within the same boundary conditions. This work aims to investigate if various leak sizes can be predicted using acoustic measurement methods. The test apparatus consists of two chambers, separated by a test wall. This wall represents a single characteristic air leakage path. Various types of wall structures with different slit geometries, wall thicknesses, and insulation materials were investigated. The acoustic measurements were performed with a sound source placed in one chamber and ultrasonic microphones located in both chambers. These results were compared to measured airflows through the test wall to provide estimates of uncertainty in the acoustic approach, which indicate a linear trend. Finally, these laboratory measurements were compared to the same measurements at a real office building. Although the acoustic measurement uncertainty is still significant (greater than +/- 50%), the acoustic method has the potential to give an order of magnitude of single leak sizes.