TABLE OF CONTENTS Any building, even with all windows and doors shut, will have a degree of ventilation (referred to as natural infiltration) by virtue of pressure differences across cracks or permeable materials in the structure causing air to flow through the structure. The degree of infiltration is governed by the quality of design and build of the structure and by the pressures generated by wind and thermal buoyancy.
This fortuitous infiltration is essential in otherwise unventilated buildings, since it allows ingress of air providing oxygen for us to breathe and for combustion equipment to burn. The infiltration is, however, effectively uncontrolled, and is often insufficient in quantity, at the wrong temperature or too contaminated to maintain satisfactory internal environmental conditions.
We must therefore be able to define the conditions we need and to design, install and operate systems to provide them. These systems cover three main areas: heating, ventilation and air conditioning. Heating and air conditioning are dealt with in Chapters 16 and 18. This chapter covers ventilation systems, defined as systems providing air movement through a space without artificially heating or cooling the air. It must be said, however, that, in practice, there is often a large degree of overlap, since office ventilation systems often provide heating in winter and complex ducted ventilation systems share much equipment and design procedures with air-conditioning systems.
This chapter is intended to provide guidance towards defining needs, assessing whether ventilation is the correct solution...
