The Australian Institute of Tropical Architecture

ANZASCA’98 - Wellington

NATURAL VENTILATION; DEALING WITH THE UNPREDICTABLE.

By Richard Aynsley and Regan Potangaroa
The Australian Institute of Tropical Architecture
James Cook University

SUMMARY

Architects often design buildings, particularly in humid tropical climates, to take advantage of natural ventilation. From a wind rose for the general area, architects note the typical wind speeds and prevailing wind directions for the hotter months of the year. The architect uses this information during design in deciding the size and location for natural ventilation openings.

If thermal comfort enhancement is the design objective, what is the probability it will be achieved or more importantly what is the probability it will not be achieved? Even eliminating influences such as metabolism and clothing, there still remain strong influences from air movement, air temperature, humidity and radiant heat gain. Careful design to limit indoor surface temperatures can avoid indoor radiant heat gain.

This paper suggests a statistical method for estimating the probability of natural ventilation equaling or exceeding that required for thermal comfort based on long term 3 hourly simultaneous data on temperature, humidity and wind. Using simultaneous temperature, humidity and wind data avoids the difficulties of estimating multivariate probability of variables, which are not strictly independent. Finally, preliminary work using neural networks is introduced.

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