Measuring Airtightness of High-Rise Buildings (Lessons Learned)

Measuring the airtightness of high-rise buildings presents significant challenges due to the effects of wind and thermal lift (stack effect). Small indoor/outdoor temperature differences, combined with the building's height, can create substantial natural pressure differences on the building envelope, while winds induce pressure fluctuations. The international standard ISO 9972 provides insufficient guidelines for dealing with these high and fluctuating natural pressure differences. In addition, it is crucial to achieve a uniform internal pressure distribution during the test. This paper discusses the airtightness testing of high-rise buildings up to 125 m tall using portable blower door devices, following the "airtightness measurement of high-rise buildings" Passive House guideline. Differential pressure sensors were placed on the ground and top floors to record the effects of wind and thermal lift, and additional sensors helped to achieve a uniform pressure distribution within the building. The readings from the ground and top floors ensured full depressurization and pressurization during testing. The setup of the measuring fans, mainly on the ground floor, was supplemented with additional fans on higher floors to maintain pressure uniformity within a 10% tolerance. To be able to conduct a multi-point regression test, it is recommended to limit the product of the indoor/outdoor temperature difference and building height to <= 1250 mK and to achieve a coefficient of determination of 0.98 or higher, a wind speed <= 3 Beaufort. The study concludes that an airtight building envelope and larger internal flow paths, such as stairwells and elevator shafts, simplify the measurement.