EVERY day I see more articles about how to live better or save energy, many of which neglect the most obvious answers. They often report inventions that could increase fuel efficiency by 10 per cent, ignoring the 500 per cent increase you get from packing more people in a car.
Others praise the junk foods with 10 per cent less fat, not the people who eat 90 per cent less junk food. When it comes to keeping warm in winter, likewise, we often overlook the simple.
We use many times more energy keeping warm than our ancestors did, partly for the reasons mentioned in the last column: our houses rarely use the natural energy around them, and they leak the energy many of us import from far away.
Most modern homes are many times larger than traditional ones, giving us far more space to heat. Another reason, though, is that inside these houses, more and more of us are alone.
In 1900 only one per cent of US residents lived alone, and half lived in households of six or more people. By 2012, 27 per cent of Americans lived by themselves, and other Western nations saw similar trends. When extended families gathered under one (small) roof, the entire building could be heated or insulated more easily, and of course when people gathered in the same room, their body heat warmed the air. More people living alone, and fewer people per house in general, means more vast spaces to heat separately.
For another thing, most of us keep our homes very hot these days. One building organisation assumes a normal indoor winter temperature of anywhere from 20 to 27 degrees C (around 67 – 82 F), but a few decades ago it was 12 degrees (53F), according to the UK’s Building Research Establishment.
Some people in central or eastern Europe built masonry stoves, whose winding chimney heated a giant thermal mass of brick or stone — and some had a space for bedding attached to the stove itself, so that the fire would warm the brick underneath the bed. Hot-water bottles accomplished the same purpose with less of a fire hazard, and we still use them in our house through the winter.
Clothes insulate the body the same way that batting insulates the home, by trapping poorly-conducting air pockets between the hot and cold spaces. As Kris De Decker of Low-Tech Magazine pointed out, though, insulating the body means warming only a tiny layer of space between us and our clothes – which costs much less energy than insulating our now-giant living spaces. If we feel warm, however, it achieves the same result.
Since every degree of indoor heat translates to about nine or 10 per cent more energy, a 20-degree change in temperature could bring heating expenses from exorbitant to almost nil. As one of our home builders said, “If you’re wearing a t-shirt in the winter, you’re spending too much money.” As house insulation can be expressed using measures like R-values, clothes insulation is measured in the lesser-known ‘clo’ unit. A clo, developed by scientists in the 1940s, is defined as the amount of clothing needed to keep a couch potato feeling about 21 degrees C (70 F) indefinitely. In physics terms, it’s 0.155 m2 K/W. In architect’s terms, it translates to 0.88 R. Or you could say that it’s about three kilograms of clothing weight — a three-piece business suit.
Every one-degree drop in temperature can be compensated by putting on about 0.18 clo worth of insulation, and organisations like ASHREA and ISO have compiled meticulous lists of clothing and their clo-values, so a t-shirt is 0.1 clo, a sweater (or jumper, if you are in Ireland or the UK) about 0.2 to 0.4 clo, and trousers 0.25 to 0.35 clo. As De Decker points out in his article, if someone in a t-shirt simply put on more appropriate clothes – long underwear, heavy shirt and jumper — they could reduce their heating costs by 50 to 70 per cent.
Finally, one last and often-overlooked factor in winter warmth — most of our ancestors worked hard. Physical activity might be the most important factor in keeping the body warm. Chopping wood warms you twice – once from the chopping, and a second time from the wood.
