INTRODUCTION

It is important that a building is energy efficient and has an acceptable level of air quality and ventilation air for the occupants. If a building is overventilated, it will be energy inefficient, resulting in excessive costs and increased greenhouse gas emissions. Conversely, if a building is underventilated, it can have an impact not only on the health of the occupants through poor indoor air quality but also on the building itself through condensation and mould growth.

Effective ventilation must therefore fulfil a number of essential functions such as:

• providing air for human respiration;

• diluting and removing airborne pollutants, including odours;

• controlling excess levels of humidity (arising from water vapour in indoor air); and

• providing thermally comfortable conditions.