ABSTRACT
This chapter considers the requirements of an air supply for the wellbeing of building occupants, as well as the effects of air supply on the building fabric. It also considers the various ventilation strategies available to designers. The need to ensure a suitable air supply is not restricted to building occupants: many space and water heating appliances require oxygen for combustion. There are also conditions in which the building fabric needs to be properly ventilated. In order to understand the behaviour of air in and around buildings we need to consider how gases behave as their temperatures and pressures change, and how that in turn affects the movement of air in the earth’s atmosphere. Gas is one of the four states of matter: the atoms and molecules in gases move freely and are separated by much greater distances than those of solids and liquids. The relationships between the volume, temperature and pressure of a gas are predicted by gas laws.
