High-Rise Buildings Airtightness Measurements: Practical Advices and Error Estimation

For an ideal building airtightness test, the pressure difference between inside and outside would be constant over time and uniform along the entire building envelope, so that each leakage is equally considered and that the test result does not depend on the test conditions. This is particularly challenging for high-rise buildings as they are more subject to strong stack effects: the temperature difference between inside and outside induces a pressure difference along the envelope directly proportional to its height. In addition, high-rise buildings can have a significant pressure loss through stairwells. These specificities of high-rise buildings conflict with several points of the standard ISO 9972 for the determination of buildings air permeability with the fan method. In particular, two requirements can be difficult to achieve:

• A zero-flow pressure at the ground floor |ΔP_0,ground| < 5 Pa
• A first pressure point at the ground floor > 5*|ΔP_0,ground|

This paper suggests new criteria to replace these two requirements when they cannot be met:

• A standard deviation on the zero-flow pressure measurements of less than 5 Pa
• Averaging results of pressurization and depressurization tests
• The entire building is pressurized/depressurized with a margin of 10 Pa
• H*ΔT < 2000 m.K

The estimation of the error induced by the stack effect is discussed for these two sets of criteria. A parameter study is presented on the maximum error (encountered at the first pressure point) for a wide range of buildings heights (H), temperature difference (ΔT) and leakage distributions. For configurations with H*ΔT < 2000 m.K, the new criteria allow:

• Increased possibilities of tests: a test is possible for every leakage distribution whereas the standard criteria (|ΔP_ground,0|< 5Pa ) allow a test for less than 20% of simulated configurations when H*ΔT > 1000 m.K.
• A reduced theoretical maximum error: remains below 10% and for a given repartition is always smaller than for a test according to the standard criteria.

Additional detailed practical advice are given on how to perform airtightness tests on high-rise buildings.