wind

The fan pressurization method is a common practice in many countries for measuring the air leakage of houses. The test results are sensitive to uncertainties in the measured pressures and airflows. In particular, changing wind conditions during a test result in some pressure stations having more or less uncertainty than others. Usually, it is necessary to fit the measured data to the power-law equation.

Due to the wind induced pressure, different results may be obtained if the inside-outside pressure difference is measured across different locations on the building envelope, i.e. if the external pressure tap of a differential pressure sensor measuring this pressure difference is placed in different positions. Therefore, the position of the external pressure tap may influence an airtightness test result as well.

This paper discusses two particular points of the buildings airtightness measurement method (ISO 9972) in relation with the pressure difference: (1) the nature of the pressure tap and (2) the place of the pressure tap outside. 

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.  

The air infiltration of a building, which fundamentally depends on its airtightness, can be a significant contributor to its heat loss.  It can also be affected by other factors such as external terrain, leakage distribution, sheltering factor and environmental conditions. The infiltration rate of a detached UK house was monitored for 2 months in early 2018 using constant concentration and decay tracer gas methods under various temperature and wind conditions.

The paper presents a numerical methodology to assess the natural ventilation. UrbaWind is an automatic computational fluid dynamics code. It was developed to model the wind in urban environments. The turbulence modelling, namely the dependence of turbulence length on the distance from wall, and the model constants were calibrated in order to reproduce with good agreements flow separation around buildings walls and pressure coefficient field on façades. Numerical results match well with the experiments: separation patterns and pressure field on walls in dense urban areas.

While people need to know tomorrow’s weather to decide suitable activities and precautions, so do the “intelligent” building management systems. The accuracy of the short-term prediction of the ambient conditions is particularly import for the development  of predictive control strategies.

Natural ventilation is increasingly considered a promising solution to improve thermal comfort in buildings, including schools. However in order to support its planning and implementation, quantitative analysis on airflow paths and heat-airflow building interactions are needed. This requires an adequate accounting of both internal effects, from building layout and structure, and external forcings from atmospheric factors.

The aim of this paper is to illustrate the impact of urban wind environments when assessing the availability of natural ventilation. A numerical study of urban airflow for a complex of five building blocks located at the University of Reading, UK is presented. The computational fluid dynamics software package ANSYS was used to simulate six typical cases of urban wind environments and to assess the potential for natural ventilation. The study highlights the impact of three typical architectural forms (street canyons, semi-enclosures and courtyards) on the local wind environment.

This paper describes a re-analysis of internal pressure and building ventilation in a single-opening enclosure ventilated by winds. The dynamics of internal pressure is governed by a nonlinear oscillation equation. An alternative semi-nonlinear approach is proposed for obtaining the amplitude and phase shift of the periodic motion, the resonant frequency and resonant amplitude. Our new approach reproduced two of the commonly used existing linearization results.