Washington
Queston: What I'm wondering is, if it's 15.5degC in my house or office, I'm cold. Even at 21.1 I might be cold. But if it's a 15deg spring day and I'm outside, I'd consider that warm. Why is that?
Answer: We're happy you sent this question. We are frequently chilly ourselves. We've even contemplated purchasing a onsie or two to wear at work - although in the interest of our sense of dignity, we'll probably refrain.
The thing is, though, our office isn't all that cold. According to our building manager, office thermostats are set between 22C and 24.4C during the summer. That seems plenty warm on paper - it's veritable dresses-without-tights weather - so why are we still shivering?
To start with, feeling cold is different from being cold, explained Lacy Alexander, a physiologist at Penn State University. Unless you're ill or hypothermic, your internal body temperature is always somewhere around 37C (although this varies from person to person - Rachel's hovers around a balmy 35C).
The feeling of cold or hot happens in the skin; it's your body's way of keeping your core temperature the same even when your environment changes. When it's chilly, blood vessels in the skin and extremities constrict to keep heat concentrated around the tissue underneath, which is why your hands and feet usually feel cold first. When you're hot, the opposite happens.
Ambient temperature is far from the only thing that influences this process. Our perception of cold is the product of numerous factors both inside and outside our bodies - many of them beyond our control.
The biggest one? Radiant heat. When you're outdoors, energy from the sun streams down all around you. It may be filtered through clouds or reflected off buildings, but it's still warmth. That's why the same day may feel chilly in the shade but pleasant in the sun. It's also why you need a sweater inside a 21C home, but you feel fine at the same temperature on a sunny afternoon in the park.
The amount of air blowing around you will also impact how you're feeling. Wind disturbs the air layer around your skin, accelerating the loss of heat from your body to the atmosphere around you. This might seem like a point in favour of staying indoors - no wind, right? Yet many modern homes and offices are designed to constantly keep air flowing through. The imperceptible “breeze” keeps rooms from feeling stuffy, or hot in one place and cold in another, but it also can make you feel slightly colder.
What's happening inside your body is just as important. A person's ability to retain heat is influenced by size, gender and metabolic rate. Women chill more easily than men - they have lower resting metabolic rates, and their higher levels of oestrogen amplify their blood vessels' response to cold. Having more subcutaneous fat can also help keep a person's body warm. These factors don't influence how you perceive indoor and outdoor temperatures, but if you often feel warmer or colder than those around you, they may explain why.
Even the time of year can change the temperature at which you feel cold.
Christopher Minson, an expert in human thermo-regulation, pointed out that the body makes a number of physiological adjustments in response to long periods of heat. The proportion of plasma (liquid) in our blood gets boosted, we sweat sooner and in larger quantities, and the number of heat-shock proteins - which manage the body's response to stressful conditions - increases. It takes time to scale back this “heat acclimation” at the end of the summer; that's why a 15C day in springtime seems gloriously pleasant, while the same temperature in mid-September will send you running for a sweater.
Minson's lab at the University of Oregon just received a grant to study ways to make indoor environments - particularly offices - more comfortable to people with various temperature sensitivities. He has thought about using heated chairs, special garments and tools that keep hands warm but don't interfere with finger dexterity.
“The same temperature in a building can feel so different to different people,” he said. “It's one of the biggest causes of arguments among people.”
He added that his sister, who often runs hot, has gotten into fights with co-workers over where to set the thermostat.
Things haven't come to fisticuffs over aircon settings here at The Washington Post building. But if they do, now we'll have science to explain why.
Washington Post
* Rachel Feltman and Sarah Kaplan run the Washington Post's Speaking of Science blog.