Peter Semenenko (AJ 27 5.99) makes a rational point in saying that windows should be for light, not ventilation.
However, people must be irrational, as they repeatedly say they want openable windows (viz: 89 per cent of responses to the Harris survey Tomorrow's Workplace in 1994). When they have them - and particularly if they sit near them - they also become more tolerant of internal conditions, often allowing less capital, energy and management time to be spent on.controlling the environment.
Why should this be? An open window provides wider sensory awareness of the outside - often an advantage. People are less tolerant of environments controlled by others than ones in which they can make adaptations , though they don't want to take control action too often.
People get particularly upset if they reach their 'threshold of discomfort' and can do nothing about it. An openable window then provides a safety valve: good ones also give you fine control and let you decide where to put the draught.
Openable windows are no panacea, as Adrian Leaman (AJ 4.3.99) has demonstrated. In design, therefore consider: gentle background ventilation, natural and/or mechanical (don't go to byzantine lengths just to avoid a fan - but make sure it is small and efficient); openable windows available to alleviate discomfort or enhance delight if the occupants want to use them; mechanical cooling installed and used only if absolutely necessary; selecting and integrating the appropriate items from the above; identifying and minimising serious clashes; and providing simple, effective, usable controls.
Some of the very best survey results for occupant satisfaction in energy- efficient buildings occur where sparing amounts of mechanical ventilation and/or cooling have been carefully combined with openable windows
Let's get the best of both worlds where we can!
William Bordass Associates
NB The author has a list of references if anyone would like them.