Purpose of the work
Clear and substantiated instructions for airtightness measurements of high-rise buildings, taking into account the particular requirements resulting from building height
Content of the contribution
Because of the major effects of wind and thermal conditions on high-rise buildings, when conducting blower door measurements special procedures must be followed. The standards EN 13829 and ISO 9972 do not provide sufficient guidance for this. This paper is intended as an aid for carrying out airtightness measurements of high-rise buildings.
In [Rolfsmeier/Simons 2017] practical experience from measurements taken at a 16-storey high-rise around 60 m in height is described. The appreciable influence of wind and the marked effect of thermal updraft with a natural pressure differential between the ground and the 16th floor of about 30 Pa are evident. During adverse wind conditions the pressure situation is unclear. Depending on which side of the building the instruments are placed, measurements are influenced to varying degrees by the wind.
The most favorable situation for airtightness measurements at large buildings is therefore calm weather and a small temperature difference between the inside and the outside. Since measurements must take place during construction, though, such conditions are rarely encountered.
The influence of temperature difference and building height on the pressure differential between the ground and the top of the building that causes thermals is about 48 Pa, like for an 80 m high building and a temperature difference of 15 K. This results in pressure differentials that are no longer negligible for the measurement results. This example illustrates that the requirement set forth in the standards for the pressure differential not to exceed 10% at any point within the building envelope can never be met.
In order to still be able to conduct measurements at a high-rise building, practical suggestions for doing this are derived and presented. Instructions are worked out for how to proceed, where the fans can be positioned, which measured values cannot be evaluated and which additional measurements must be made. Also explained is the measurement error due to the non-linearity of the air flow formula.
Results and assessment of their significance
With the help of these instructions, airtightness measurements at tall buildings are facilitated and standardized. It is important to note that additional measurements at different sides of the structure have to be taken in the uppermost floor as well as in the ground floor. In addition, only measurements for which the entire building is pressurized or under a negative pressure may be evaluated.
[Rolfsmeier/Simons 2017] Rolfsmeier, S.; Simons, P.: Airtightness measurement in a large and high passive structure (multi-family housing) in windy conditions and with thermal updraft (in German) in: Proceedings of the 21st International Passive House Conference, Passive House Institute, Darmstadt, 2017
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