Just spotted this in the grauniad
cheers
Jacob
Scientists' survival tip: go with the flow
Tim Radford, science editor Thursday August 7, 2003 The Guardian
British scientists have just issued a hot tip for survival when the fan has broken down and the thermometer is up. It saves energy and exploits everyday household technology.
Just open a window, says Gary Hunt, who leads research at Imperial College London into the fluid mechanics of natural ventilation. It helps to have a sash window in the right place and at the right height.
"Many of us have forgotten how to correctly use the sash windows so carefully installed by the Edwardians and Victorians to maximise airflow," he said. "If used correctly it is possible to significantly improve comfort in the office or at home without using air conditioning units that place high demands on energy and increase carbon dioxide emissions."
He used a small laboratory model to simulate the average home as a hothouse and keep track of cool airflow through rooms and buildings. It is best to have your sash window open equally top and bottom. That way cooler air flows into the room through the lower opening and flushes the warm air out through the top.
If the windows are too small, or badly placed, however, hot air is trapped at ceiling level and extends down to make the inhabitants unpleasantly hot and muggy.
"Our research shows a good strategy is to leave sash windows in the mid-position overnight - providing it is safe to do so," he says.
"The cool external air flushes the warm air of of the room and also cools the walls, floor and ceiling. The cool walls absorb the heat the following day and prevent the internal from temperatures rising as high."