The most popular post on TreeHugger right now is 6 Energy-Saving Portable Electric Space Heaters, as people look for ways to keep warm in a shoulder season where the apartment building furnaces are not yet delivering heat, or people don't want to heat the whole house when they think they just need one room.
There are many ways to keep warm, including cuddling puppies in front of fireplaces. Not everyone can do that, and renters and students can't make expensive changes, so one can see why electric space heaters are popular. There are alternatives, but before we go there, we have to discuss what thermal comfort actually is about, and it is a lot more than just air temperature. Engineer Robert Bean notes that "We don't inhale comfort, we sense it through our skin...yet 99.99% of all thermostats exclusively measure air temperature and fail to measure what we experience." Our comfort is determined by the 166,000 thermal receptors in our skin, not the thermostat on the wall. Those receptors are sensitive to air temperature, radiant temperature (a function of the temperature of the interior surfaces) , humidity, air velocity, activity rate and clothing.
Changing any one of these affects how you feel; Go to the comfort calculator on Robert Bean's site and play with it. (This is why passive houses are so comfortable: the interior surfaces are really warm and the radiant temperature is high. It's also why I think smart thermostats are a dumb idea- they only measure one thing.) So instead of going out and buying a portable electric heater, here are 5 alternatives based on making you feel warmer, rather than just heating up the room.
1. Get some long underwear
Comfort is a function of the rate of heat loss from our skin, so the first thing to do is reduce that by putting on the right kind of clothes. Steve Mouzon has noted that "because we are too lazy to put on a sweater or take off a jacket, we have let the thermostat and the mechanical engineer behind it change the way we make buildings." Kris De Decker of Low Tech Magazine notes:
Insulation of the body is much more energy efficient than insulation of the space in which this body finds itself. Insulating the body only requires a small layer of air to be heated, while a heating system has to warm all the air in a room to achieve the same result.
Kris says there is nothing better than the high-tech thermal underwear that the sports clothing industry is producing; the tight-fitting synthetic thermal kind that you can buy at REI or MEC. "One layer of thermal long underwear allows you to turn down the thermostat with at least 4° C (7.2°F) , saving up to 40% on space heating energy." I agree; I must have half a dozen sets of varying thickness, from thin silk to thick double-layer Helly Hanson's that I wear all winter.
And put on a hat. Robert Bean notes that of the 165,000 thermal sensors in our skin,
here’s a very amazing consideration…these nerve endings are not distributed in a homogenous pattern as one might imagine, but in higher concentrations in the exposed areas of the body, that being your feet, ankles and calves, hands and wrists and neck, face and head.
So while it has been proven that you don't lose more heat through your head, you feel like you are.
2. Be a draft-dodger
You don't have to skip out to Canada to beat the draft; you can do it with a tube of strippable caulk that you install in the fall and pull off in the spring. Not only are you reducing your heat loss, but reducing air movement makes you feel warmer.
You can make your own draft excluders to put at doors and window sills, and stuff them with anything from rice to foam. Here are DIY instructions from the Guardian.
3. Get a hot water bottle.
Seriously, we are not just showing 19th century solutions here; this hot water bottle is in a jacket made of phase change material that absorbs heat from the hot water when it is really hot, and then releases it as the water cools, evening out the temperature and ensuring that it is never too hot. More at Unikia
4. Do something, like cleaning the house.
Our activity rate is one of the factors that determines our comfort level, and almost any movement generates body heat. You could do a few squats or other exercises, or you could get out the vacuum cleaner;
According to CalorieLab, you can burn a lot of calories cleaning your house. Whatever keeps you moving.
5. Bake a pie.
Seriously. This works two ways; the heat of the oven will warm you and your home, and just doing stuff warms you up; CalorieLab calculates 102 calories per hour is burned. In the end you get... pie. Here's Maggie's recipe for graham cracker crumb apple pie.
And if you want to feel even warmer, bake gingerbread. There is a Japanese study that determined that ginger "increases adrenaline secretion via the activation of TRPV1." and warms you up.
The key point is that an electric space heater that costs you money to run and has its own carbon footprint is only one of the many alternatives that can keep you warm and toasty. And the others are a lot more fun.