Abstract
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 wind turbulence and the pressure fluctuations on the facades and the roof of the building are being investigated using energy spectra of their signals. Farther analysis of the experimental results is needed to be able to include high frequency wind in the infiltration model.
Highlights
This paper is built upon the results of the work carried out over many years and constitutes a personal perspective/experience on the issue of probabilistic modelling of air exchange in buildings
Probabilistic output in the form of probability density function of air change rate estimated with the help of FORM using the program developed by Czmoch [6] formed a ground for reliability analysis of adequate ventilation
The work presented in actual paper concentrates on the possibility to consider the higher frequency of wind conditions in the air exchange model based on wind pressure measurements
Summary
This paper is built upon the results of the work carried out over many years and constitutes a personal perspective/experience on the issue of probabilistic modelling of air exchange in buildings. The model was applied to analyze the hourly air exchange caused by air infiltration in a building situated near Gothenburg. Contributions of both wind and temperature difference were evaluated. Sensitivity analysis of the influence of wind and outdoor temperature on the air infiltration tested the model outcome in terms of its robustness in the presence of uncertainty It was first presented on the IEA Annex meetings and published at the conferences in 2012/2013. The probabilistic risk analysis along with the effective tools for sensitivity analysis is proposed to be used to support design decisions and to develop better models for evaluation of building performance [10]. It is planned to introduce the rapidly varying fluctuations of wind speed to the model
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