First published: 24th November 2006
Warren Russell ("Cool Conditions", letters 2006/11/23) proposes a simple solution to pollution and global warming: banning airconditioning when the temperature is below 25.5°C. Unfortunately, like many simple solutions, it is unworkable.
Is 25.5 the average or a maximum? Do we sweat in our offices during the day because the nights are cool? How long do you get to switch off when the temperature dips?
More seriously, our buildings contain many heat sources that raise the temperature: lights, office equipment (computers), machinery, and, of course, people. Opening windows only has a small effect (nil on calm days) and larger offices will find fans (which use electricity anyway) inadaquate. Overall, an office might be several degrees warmer than outside, and some rooms may be uncomfortably warm. This can be clearly seen in data from my office, for example, on 19th November, when the Observatory average was 24.1°C, but the external wall of the building reached 31.3°C, and some rooms almost reached 30°C.
I do think that saving on air-conditioning will be important in reducing Hong Kong's pollution, in fact, we saved one third on electricity last year, compared with the previous five years. This was mainly by insulation of walls and windows, and temperature monitoring so we could use the air-conditioning more selectively. I suspect that many other buildings could benefit from insulation.
Philip Bowring's proposal for an energy tax would increase the incentive to save energy, perhaps by installing insulation.