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What impact can 3 deg C have? The right air-con setting may boost productivity, and more

SINGAPORE: When Lee Kuan Yew became Singapore’s prime minister in 1959, the first thing he did was to install air conditioners in government buildings. In his mind, air conditioning was the key to working efficiently.

But how cold is cool enough to be more productive? Something like 21 degrees Celsius or warmer instead?

Researchers at the Singapore University of Social Sciences (SUSS) now have the answer.

They got participants in an experiment to solve visual puzzles at two different room temperatures. And at 25 deg C, people performed cognitively faster than when it was cooler.

This is one of the ways in which turning the air-con up has an impact.

That was not the only result. “It was really interesting, physiologically,” said experimenter and SUSS associate professor Emily Ortega. “With skin temperature, it was quite clear that it kept going down in the slightly warmer condition.”

The convergence of lower skin temperatures and faster reaction times points to 25 deg C as more conducive to working, even though many of the participants, before the experiment, thought the colder the room, the higher their productivity.

“Now we have some kind of evidence to suggest that what you think isn’t what you get,” said experimenter Ooi Seok Hui.

The National Environment Agency advises setting the air-con at 25 deg C as an energy-saving tip. And there is also research behind this.

Air-conditioning and Refrigeration Association president Leong Cheng Wee, citing the famed thermal engineer Povl Ole Fanger, said comfortable temperatures can range between 22 and 27 deg C.

WATCH: What is the best temperature to set my air conditioner? (22:25)

“We normally tend to select right in the middle,” said Leong. “This is normally the sweet spot: At least 80 per cent of the target audience is satisfied.”

So why are buildings in Singapore so cold? Because “it’s easier to over-cool than to under-cool”, he said, since people who are cold can wear a jacket, whereas those who are warm cannot really be removing their clothes.


How much savings, then, can turning the air-con up deliver?

In a test done by Giridharan Karunagaran, the director of the Singapore Berkeley Building Efficiency and Sustainability in the Tropics research programme, the air-con in two rooms covering 50 square metres was set at three temperatures.

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The first setting was at 22 deg C, then 23 deg C, followed by 25 deg C, and the power consumption was measured.

The energy savings from going from 22 deg C to 23 deg C amounted to nine per cent, or S$72 yearly if the air-con is used for eight hours per day, 20 days per month, with the tariff rate unchanged.

Going from 22 deg C to 25 deg C delivered savings of 34 per cent, or about S$278 per year. But it need not stop there. “You’ll indeed save a lot more energy for every (one-)degree increase,” said Giridharan.

Besides cutting down on power bills, turning the air-con up can also help to lower greenhouse gas emissions.

Air-con systems remove heat from homes in a process called the refrigeration cycle, the same process that cools refrigerators.


In fact, some Singaporeans may not be keeping cool efficiently.

Aaron Wu of Amyth Aircon Services, who shares air-con tips with his company’s 16,000 followers on TikTok, visited some homes to see if people were inadvertently working their air-con units harder than they needed to.

In one home, he found an air-con unit blasting cold air while a window was slightly open. A thermal camera provided by Talking Point showed heat entering the room.

This also caused cool air to escape, said Wu, and the air-con had to work “very hard” to maintain the room temperature according to the setting.

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