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It's hot outside. Why is the office so cold?

It's that time of year: It feels like a sauna outside while the chill in many workplaces has people piling on sweaters or even turning on space heaters.

Editor's Note: With Philadelphia headed for record temperatures today, we pulled out one of our favorite stories on the subject from our archives.

It's that time of year: It feels like a sauna outside while the chill in many workplaces has people piling on sweaters or even turning on space heaters.

Pick your sartorial poison: You can wilt on the sidewalk or shiver at your desk. Or the mall. Or the movie theater.

This raises the question, Can't the thermostat gods keep more of us comfortable?

We sought science on this and discovered there is no simple answer to what seemed a simple question.

Nonetheless, the question takes on extra import as we head into what promises to be an ugly heat wave and 50,000 guests arrive in Philadelphia for the Democratic National Convention.

Anecdotally, it appears that many of those complaining about cold air conditioning at work - or at home - are women in summer clothes, and that men, particularly those in suits and long sleeves, like it cool. There's some reason to believe that large people like it cooler and that many of the elderly like it hot.

But experts on "thermal comfort" said it's not possible to say where to set the thermostat so that a particular group will be comfortable. For complex physiological reasons, we're all over the place when it comes to what temperature feels good, even when you take differences in clothing into account.

"You and I, exposed to the exact same conditions, are going to feel very different," said Gail Brager, associate director of the Center for the Built Environment at University of California, Berkeley

"The science does not enable us to predict what a single person will feel in any given condition."

Differences in temperature preferences between demographic groups are small, she said, while overall variability is huge: 10 to 11 degrees.

"There is no one thermostat setting that is going to keep everyone comfortable," she said.

Comfort, she said, depends on several variables, including the thermostat setting, humidity and air movement.

"Temperature is only one of these various factors, but it tends to be the only factor that we can control in buildings," she said.

William Bahnfleth, who directs the indoor environment center in Penn State University's department of architectural engineering, is former president of an international society of engineers devoted to making indoor environments comfortable. In existence for more than 100 years, ASHRAE, as it's known, addresses the temperature issue in its Standard 55.

Its goal is to keep a majority - 80 percent - of people in a building happy. The standards assume people wear lighter clothes in the summer.

The summer comfort zone is 76 to 83 degrees, with no humidity. More typically, an office strives for 50 percent humidity. Then the comfort zone is 75 to 80.

The air that comes out of the vent in the summer is 40 to 50-some degrees, depending on the air conditioning system, Bahnfleth said. A good part of that cooling is due to the need to remove humidity, but the lower temps also make it easier to cool a space efficiently.

'Wasting vast amounts of energy'

To further complicate things, Bahnfleth said, "adaptive thermal comfort" has been gaining acceptance in recent years. The idea is that, if it's hot outside and you're used to it, you can probably be comfortable in warmer temps inside as well.

What actually happens, though, is that most building managers keep thermostats at the same setting all year, Brager said. In fact, a study of 100 office buildings found that they averaged 73 in the summer - lower than the ASHRAE standards - and 74 in the winter. Yes, that's warmer in the winter. Field studies found that 40 percent of occupants were dissatisfied.

Why are the buildings over cooled?

"That's the million dollar question right there. I don't know why we're doing that," said Brager, who has had to wear sweaters at summer meetings and tank tops in the winter.

"We are wasting vast amounts of energy and we are creating uncomfortable conditions."

She said it is possible that some overcooling is primarily about reducing humidity to prevent mold. Also, in some retail businesses, such as high-end stores, chill has been seen as a sign of luxury.

Brager is a fan of systems that allow more air movement and individualized control.

"One-size-fits-all temperature control needs a paradigm shift," she said.

She said energy-efficient chairs (the pricetag is $1,200) that can heat or chill occupants can improve comfort. Foot warmers and low-wattage desk-top fans also help. In buildings using a system called Comfy, workers use an app on their phone or computer to ask for warmer or cooler air. Over time, the system learns their preferences.

'Cold as we possibly can'

Phil Castellon, vice president, regional property manager for Liberty Property Trust, which operates the Comcast building and offices at the Navy Yard, said buildings are kept between 70 and 74 year round. "Most people are comfortable at those ranges, he said.

Two operators of malls, Simon Property Group and Preit, did not respond to questions about how they choose temperature settings.

Charles O'Donnell, chief operating officer of the Duane Morris law firm, said his firm keeps as many people as possible comfortable by giving employees in "very small work zones" the ability to control temperatures.

For the convention, the existing cooling system at the Wells Fargo Center has been augmented by two 300-ton chiller units.

Morgan Finkelstein, a spokeswoman for the DNC, said there's no specific thermostat setting for the convention. It's not like a sporting event where people come, stay awhile and leave in a group. The meeting will involve a lot of coming and going over four full days.

"Our goal is to make it as cold as we possibly can," Finkelstein said.