Stack Ventilation & Flushing
We talked earlier about stack ventilation and flushing to help dissipate heat from thermal mass on summer nights.
Stack ventilation has been employed in hot arid areas for centuries and relies on the fact that, due to their relative densities, hot air rises and cool air sinks.
By constructing towers with broad sides facing the midday sun heat gained in the tower induces the warmer air to rise out of vents near the top and suck cooler air into the building below. Conversely, towers containing moisture producing elements within them cool the air by evaporation causing it to sink into the building. Both these systems induce air flow and cooling into buildings that would otherwise have had little air change and made them far more comfortable during the heat of the day.
The use of this natural stratification of warm air can be harnessed to flush out unwanted heat in our homes very simply by opening vents at high level to allow hot air to naturally flow out and opening vents low down adjacent the shadiest part of the house to allow cool fresh air in to replace that vented at the top. This simple system reduces heat build up on summer days and allows cool flushing to vent heat from the house during the night.
Vents can be in upper rooms, at the top of the stair, clerestory windows in split skillion roofs or even specially created solar chimneys to speed air flow by increasing temperature in out flowing air.