Probabilistic modelling of wind induced air exchange in buildings
Paper in proceedings, 2019

The work presented is the continuation of the research on the probabilistic modelling of air infiltration carried out by the author over many years. The approach has consisted in considering uncertainties coupled to the climatic/environmental input data to the physical models, or to the threshold criteria for a good performance. The concept of risk/reliability evaluation of building/environment system performance was proposed and exemplified for the air exchange model.
Air exchange in buildings is driven by pressure difference across the building envelope caused by wind and difference in density between external and internal air. The evaluation of the influence of wind on the air change rate is usually limited to the analysis of the hourly mean wind speed. Wind is a random phenomenon characterized by the broad energy spectrum. The high frequency part can be responsible for the oscillation of the air through the openings resulting in the increased air exchange. Wind pressure coefficient on the leeward site mostly depends on the form characteristics of the object in relation to wind direction. The analysis of wind speed and wind pressure on the facades in frequency domain can deliver interesting data to air change rate model.
Some of the results of continuous measurements carried out on a single-family house for 8 months are presented in frequency domain. The statistics of wind speed, wind direction and pressure differences across the 6 building components are calculated. The influence of wind turbulence on pressure fluctuations on the facades and the roof of the building are investigated. The samples of the energy spectra of pressure differences are examined. Farther analysis of the experimental results is needed to be able to propose the more detailed model.

wind

infiltration

power spectrum

turbulence

Probabilistic modelling

air exchange

Author

Krystyna Pietrzyk

Chalmers, Architecture and Civil Engineering, Building Design

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Other Civil Engineering

Building Technologies

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