If you’re constantly bundling up against your office building’s air conditioning, blame Povl Ole Fanger. In the 1960s, this Danish scientist developed a model, still used in many office buildings around the world, which predicts comfortable indoor temperatures for the average worker. The problem? The average office worker in the 1960s was a 40-year-old man sporting a three-piece suit. But fear not, those for whom the “work sweater” has become a mandatory addition to office attire: Researchers say they have built a better model.
The biggest problem with Fanger’s approach—which assumes a 21°C (70° Fahrenheit) office would be the most comfortable—is that it doesn’t take women into account. Men typically have faster metabolisms than women, and thus generate more heat. In addition, women tend to have much stronger vasoconstrictive reactions than men—when they get cold, their blood vessels close faster, and their sensitivity to temperature increases. Cue the work sweater.
It’s not just women who suffer. “When I have to go to conference halls they’re often way too cold,” says Wouter van Marken Lichtenbelt, an ecological energeticist at Maastricht University in the Netherlands. “It feels like there’s a winter draft blowing. Even in warm temperatures I’ll take a sweater with me if I know I have to attend a meeting.”
So in the new study, Lichtenbelt and Boris Kingma, a human biologist also at Maastricht, decided to update Fanger’s approach. They wanted a model that fosters a thermoneutral zone (not too hot, not too cold) for as many people as possible. That meant incorporating biophysical data on heat production in the body for both genders. They measured average skin temperatures and body temperatures of females in the office and adjusted the metabolic average in the biophysical model to represent a true average for a thermoneutral zone.
The result: a model that suggests office temperatures should be set at a happy medium, about 24°C (75° Fahrenheit), the team reports online today in Nature Climate Change.
Lichtenbelt and Kingma say they hope their work will not only keep everyone comfortable, but also conserve energy in the process. According to the study, residential buildings and offices currently account for 30% of global carbon dioxide emissions.
Still, not everyone is going to agree that 24°C is an optimal temperature, notes George Havenith, an environmental physiologist at Loughborough University in the United Kingdom who was not involved with the study. So he proposes a more low-tech solution, which he and his colleagues implement in their own office. “We usually cope by opening windows, or having a fan,” he says. “But mainly, we put on shorts.”