Dr. Gary Hunt of the Department of Civil and Environmental Engineering who is leading research at Imperial on the fluid mechanics of natural ventilation explains:

"Many of us have forgotten how to correctly use the sash windows so carefully installed by the Edwardians and Victorians to maximise airflow.

"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."

Using laboratory modelling techniques that accurately replicate the flow of air in small-scale physical models, Dr. Hunt and his team are able to measure and clearly visualise how air circulates within rooms and buildings.

"The trick to getting the maximum flow of air through the window is to slide the sashes so the window is open equally at the top and bottom.

"By separating the in-flow and out-flow, cooler incoming air efficiently flushes the warm air out of the room. The warm air inside the room tumbles out of the top opening and the cooler air form the outside comes in through the lower opening," explains Dr. Hunt.

By applying mathematical analysis and using small-scale laboratory models, the researchers were also able to calculate the size and placement of windows to maximise ventilation.

"The laboratory modelling technique relies on examining the movement of water through a model typically one twentieth to one hundredth of the building size. At this scale water moves through the model room in the same way as air moves through a real room," said Dr. Hunt.

Results show if the windows of a room are too small or their location is not appropr
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Contact: Judith H Moore
j.h.moore@imperial.ac.uk
+44-0-20 -7594-6702
Imperial College London
6-Aug-2003