Of the government's initiatives to get us to be more environmentally responsible, perhaps the most effective has been the one espousing that office air conditioners be set at 25.5 degrees Celsius. It is a number many people seem to be aware of, as a quick straw poll proved. Whether the knowledge is put into practice is another matter, of course, but the fact that it seems the message has been widely disseminated is impressive. Here the praise must end, though: the information is only partly right.
This is one of those cases where authorities have only done half their job; 25.5 degrees is a summer setting, not applicable to the other nine months of the year. During colder weather, thermostats should be lowered according to the outside conditions. If outdoor temperatures are less than those inside, we are on average doing more environmental harm than good. Every extra degree of cold or heat raises usage - and fuel bills - by 10 per cent, after all.
The government announced in October 2004 that air conditioners in all public buildings should be set at 25.5 degrees during summer. It launched a 'no freezing summer' campaign the following June to encourage the private sector to follow suit. The figure has since been frequently bandied about by officials, most emphatically by Chief Executive Donald Tsang Yam-kuen in 2006 when he removed his jacket and trademark bow tie in front of legislators to promote his 'Action Blue Sky' policy.
His clear message was that dressing more casually meant rooms did not have to be so cold. Less electricity would be needed, meaning lower bills and less pollution from power plants. It was a strategy that cost nothing to implement and would save money and the environment. Brilliant.
The rare image of a dressed-down Mr Tsang could well be the reason so many of us have '25.5' memorised. I am sure it flits subliminally through our minds whenever we drift near an office thermostat. A quick check, an adjustment if necessary, and the working environment is as it should be, we tell ourselves. We get back to our duties, satisfied that we have done our bit for Hong Kong.
Gerry McMahon, the director of the specialist building services company Facilities Analysis and Control, put the problem in a nutshell: attaining a 25.5 degree temperature in winter would, in most cases, mean heating a building to a point where the majority of people would feel uncomfortable. Ambient conditions naturally determined indoor temperatures, so when they changed, air conditioners should be adjusted accordingly. Some heating may still be required to achieve desired temperatures, but the notion of pushing the target up to 25.5 degrees in winter was ridiculous. Why waste energy in winter just because someone had decided the setting would save energy in summer, he rightly asked.