Wind towers and wind driven ventilation.

Passive cooling techniques driven purely by natural wind forces present a highly attractive environmental solution in the perspective of low energy architecture. The physics governing passive cooling are well understood and have been extensively discussed in the literature. Indeed the necessary design details that must be incorporated to achieve the full potential of the technique, such as exposed thermal massive and good internal and solar gain control, are also well understood. Furthermore, the mechanisms by which occupant comfort is achieved can be quantified allowing various designs to be iterated towards the optimum solution. However, issues concerning the design and sizing of apertures for ingress and egress of the ventilating air are less clear, and in particular, there are few "engineering" methods available to size wind towers and wind scoops. The present paper discusses the wind tower calculation method, developed by Battle McCarthy, in conjunction with Imperial College. The calculation method, derived from extensive wind tunnel testing, provides the designer with an accurate engineering tool for determining the size and number of wind towers and scoops for use in natural ventilation.