Summers are hot in Omaha, Neb., where heat indexes can top 100 degrees. But Molly Mahannah is prepared.
At the office, she bundles up in cardigans or an oversized sweatshirt from her file drawer. Then, she says, “I have a huge blanket at my desk that I’ve got myself wrapped in like a burrito.” Recently, “I was so cold, I was like ‘I’m just going to sit in my car in like 100-degree heat for like five minutes, and bake.’”
Mahannah, 24, who wrote on Twitter that at work she felt like an icy White Walker from “Game of Thrones,” said a female co-worker at her digital marketing agency cloaked herself in sweaters, too. But the men? “They’re in, like, shorts.”
Right. It happens every summer: Offices turn on the air-conditioning, and women freeze into Popsicles.
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Finally, scientists (two men, for the record) are urging an end to the Great Arctic Office Conspiracy. Their study, published last week in the journal Nature Climate Change, says that most office buildings set temperatures based on a decades-old formula that uses the metabolic rates of men. The study concludes that buildings should “reduce gender-discriminating bias in thermal comfort” because setting temperatures at slightly warmer levels can help combat global warming.
“In a lot of buildings, you see energy consumption is a lot higher because the standard is calibrated for men’s body heat production,” said Boris Kingma, a co-author of the study and a biophysicist at Maastricht University Medical Center in the Netherlands. “If you have a more accurate view of the thermal demand of the people inside, then you can design the building so that you are wasting a lot less energy, and that means the carbon dioxide emission is less.”
The study says most building thermostats follow a “thermal comfort model that was developed in the 1960s,” which considers factors such as air temperature, air speed, vapor pressure and clothing insulation, using a version of Fanger’s thermal comfort equation.
It is converted to a seven-point scale and compared against the Predicted Percentage Dissatisfied, a gauge of how many people are likely to feel uncomfortably cool or warm.
Seems simple enough.
But Kingma and his colleague, Wouter van Marken Lichtenbelt, write that one variable in the formula, resting metabolic rate (how fast we generate heat), is based on a 40-year-old man weighing about 154 pounds.
Maybe that man once represented most people in offices. But women now constitute half the workforce and usually have slower metabolic rates than men, mostly because they are smaller and have more body fat, which has lower metabolic rates than muscle. Indeed, the study says, the current model “may overestimate resting heat production of women by up to 35 percent.”
“If women have lower need for cooling it actually means you can save energy, because right now we’re just cooling for this male population,” said Joost van Hoof, a building physicist at Fontys University of Applied Sciences in the Netherlands, who was not involved in the study.
“Many men think that women are just nagging,” he said. “But it’s because of their physiology.”
Physiology and clothing. The authors also note that the model is not always calibrated accurately for women’s summer wardrobes.
But Kingma’s study offers another solution: Change the formula.
The researchers tested 16 women, students in their 20s, doing seated work wearing light clothes in rooms called respiration chambers, which track oxygen inhaled and carbon dioxide exhaled. Skin temperature was measured on hands, the abdomen and elsewhere. A thermometer pill the women swallowed reported internal body temperature.
Researchers found the women’s average metabolic rate was 20 to 32 percent lower than rates in the standard chart used to set building temperature. So they propose adjusting the model to include actual metabolic rates of women and men, plus factors such as body tissue insulation, not just clothing. For example, people who weigh more get warmer faster, and older people have slower metabolic rates, the study reported.
How much warmer an office would become would vary, of course, but the study cites research finding as much as a 5-degree difference in women and men’s preferences. Kingma said a woman might prefer a 75-degree room, while a man might prefer about 70 degrees, which Kingma said is a common current office temperature.
Some experts doubt the proposed formula would be easily adopted.
Khee Poh Lam, an architecture professor at Carnegie Mellon, said even if the industry accepted a change to the long-standing model, buildings often house different businesses or “squeeze more people in” than they were designed for and partition offices so thermostats and vents are in different rooms. Given these improvisations, he added, “whether this actually affects energy, I think that’s a big leap.”
Still, he said, “we need to keep pushing” for improvements because “the phenomenon of women getting cold is very, very obvious,” and cold or hot employees are less productive.
Individualized temperature controls are the eventual answer, said Lam, who helped design a “personal environmental module” in the 1990s that was deemed too expensive for commercial development. Now others are developing systems to let workers make their cubicles warmer or cooler.
Kimberly Mark, 31, would appreciate that. This summer, at a software company in Natick, Mass., she and female colleagues are using space heaters. The thermostat is in the office of “the guy next to me,” she said, “and I’m the only woman in the offices that he controls.”
Ashaki Lloyd contributed reporting.