Starting from the premise that condensation in the building envelope is a prime cause of its deterioration, the mechanisms that cause condensation are discussed and control measures explained. The conflicts that arise between some of these measures, the probability of achieving them under realistic construction conditions, and the possible need for fail-safe provisions should complete success not be achieved, are described.
Existing models for predicting air infiltration account for three dominant variables, namely envelope leakage characteristics, indoor-outdoor temperature difference and wind speed. Building shape, wind direction and sheltering, also influence the wind induced component of air infiltration. In this report, these variables are examined analytically and experimentally using wind tunnel data and field infiltration measurements. A sensitivity analysis of a power law infiltration relationship reveals that these factors are most significant at small temperature differences.
General principles of air movement around buildings are stated, indicating where windy areas are likely to occur. Case studies are then described in detail, and lessons to be learnt from these are summarised. Descriptions of wind tunnel measurements around simple model buildings are followed by accounts of the use of meteorological wind data and of the effects of wind on people. A method of predicting wind conditions around a building is developed. Some notes on wind tunnel investigations are given.
The appearance of bubbles used for flow visualisation around bluff bodies in a wind tunnel is illustrated. It is demonstrated that the large diameter and low density properties of bubbles could enable them to represent raindrops in a wind tunnel.
For proper control of the ventilation in a building, it is necessary to know the factors involved. These include (1) the climate, including temperature, wind direction, and wind velocity, (2) the building performance, (the interconnections b
The growing interest in the response of structures to turbulent wind forces and the realization of the important role played by root-coherence in the prediction of such response has led to the proposal of several expressions for the power
A wind tunnel of open-circuit configuration designed specifically for building aerodynamics is described and its performance is discussed. It has a working section 2 m wide x 1 m high x 8 m long with a maximum wind speed of 20 m/sec under
The use of lightwells and courtyards for natural ventilation in high-rise buildings is exaimed using both wind tunnel and field measurements of the pressures and neutral pressure zone caused by wind and temperature differences. Though air flow patterns are complex for complex building designs, air exchange rates in lightwells and courtyards were generally seen great enough to assure clean air for natural ventilation via air infiltration. However the cost of land in urban settings will probably make mechanical ventilation systems the economic choice.
The purpose of this research project is for the Thermal Engineering Section of NBS to conduct air leakage measurements on selected large buildings tovalidate calculation formula developed by Shaw and Tamura, (see Shaw, C.Y., and Tamura, G.T., 'The Calculation of Air Infiltration Rate Caused by Wind and Stack Action for Tall Buildings', ASHRAE Trans., Vol. 83 part 2).
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