In the battle for the thermostat, preferences often fall along gender lines. But the instigator of the conflict is often the building itself, and better accounting for the unique temperature needs of women could lead to an armistice while saving energy, according to new research.
Residential and office building energy consumption accounts for 30 percent of global greenhouse gas emissions, and for decades, engineers calibrated these buildings for men to make comfortable indoor environments.
Specifically, standards were established around the metabolism of a 40-year-old, 155-pound man, who would dissipate 58 watts per square meter of energy. Each person in a building radiates a given amount of heat, which in turn requires a certain amount of cooling to keep in check.
Coupled with a vague measure of clothing insulation, these variables formed the reference tables that engineers around the world have used to calculate their heating and cooling loads since the 1960s.
However, these standards don’t account for differences in size (the average person is now taller and heavier), body composition (fat versus lean), age (older people have slower metabolisms), activity levels and gender: Women radiate as much as 35 percent less energy than the standard man. In general, women prefer higher indoor temperatures, averaging 77 degrees Fahrenheit, while men say they are most comfortable at 71 degrees Fahrenheit.
By focusing only on men, many buildings are wasting energy and making their occupants uncomfortable.
“If your building is 50 percent male and 50 percent female, you’re already over your estimated cooling demand,” said Boris Kingma, a biophysicist in the department of human biology and movement sciences at Maastricht University in the Netherlands.
‘People will adapt their behavior until they are comfortable’
In a study published yesterday in the journal Nature Climate Change, Kingma presented a model that could better define a thermal sweet spot for homes and offices.
“Basically, what we tried to model was what body characteristics can tell,” said Kingma. “What the model is showing is under what environmental conditions the body can maintain its core temperature without shivering and without sweating.”
The model used real-world measurements of metabolism and built on them to establish temperature comfort standards, a bottom-up approach that can be tweaked to accommodate different office cultures, workplace demographics and climate conditions.
“For an accurate vision of thermal demand, you need an accurate vision of metabolic rates,” Kingma said.
Such an approach could shrink the carbon footprint of buildings, which consume nearly half of all energy in the United States, according to the U.S. Energy Information Administration. As new offices get built and old homes are retrofitted, getting the temperature right stands to make a huge difference in energy use.
Kingma noted that many efficiency upgrades fall short of their predicted benefits because occupants undermine the performance of the building, whether it’s using space heaters during the summer or opening a window to let out excess heat in the winter (ClimateWire, Dec. 22, 2014). Up to 80 percent of the variation in a building’s energy consumption comes from how people use the structure. “People will adapt their behavior until they are comfortable,” he said.
Alan Hedge, a professor of ergonomics at Cornell University who was not involved in the study, said the findings were not surprising. “There is a huge functional gender difference in thermal comfort in buildings,” he said. “We’ve known that for a long time, and we continue to ignore it.”
This isn’t simply a matter of comfort; a poor office climate can hamper productivity. In a 2004 study, Hedge found that raising office temperatures from 68 to 77 degrees Fahrenheit reduced typing errors by 44 percent and raised typing output by 150 percent.
Keeping buildings frigid also creates a self-reinforcing cycle. “By having the air conditioning so cold, the body never learns to adapt to the hotter temperature,” Hedge said. “The more you can get in tune with the actual environment, the better.”
Cutting emissions with new wardrobes
In a workplace, part of the efficiency solution lies in changing culture: Offices conditioned to accommodate men in suits usually leave women in skirts and blouses out in the cold. Leveling the dress code would narrow the gender temperature gap.
Hedge noted that in 2005, the Japanese government instituted a program called Cool Biz, in which government buildings set their thermostats at 82 degrees Fahrenheit between June and October. To accommodate the heat, workers were allowed to take off their coats and loosen their collars.
The Japanese Ministry of the Environment estimated that in the first year it went into effect, Cool Biz saved 460,000 tons of carbon dioxide emissions.
While some workers felt self-conscious riding the train in short-sleeved shirts with their private-sector colleagues in worsted wool suits, Cool Biz spawned its own fashion subculture and clothing lines. Following the 2011 Tohoku earthquake and tsunami, which caused electricity shortages, the Cool Biz season was extended from May to October.
In the United States, Google turned down the air conditioners in its data centers and encouraged employees to wear shorts in those facilities. Earlier this year, Wal-Mart Stories Inc. announced that it would raise temperatures in stores and allow a more relaxed dress code for its workers.
It may be a while before we see gabardine kilts and sleeveless button-down shirts on the floor of the Senate, but cool, breathable fabrics like seersucker and linen could be an energy-saving compromise until fashion catches up with efficiency demands in government.
Ultimately, the gender divide will never completely go away, and the future lies in personalized cooling, according to Hedge (ClimateWire, Feb. 10). Passive ventilation and creating microclimates for individuals rather than cooling a whole building would save energy and enhance comfort.
Reprinted from Climatewire with permission from Environment & Energy Publishing, LLC. www.eenews.net, 202-628-6500