Jimmy Carter in his Famous Cardigan Sweater
Jimmy Carter was right; when it is cold, the first thing you should do is put on a sweater. He was ridiculed at the time, being Jimmy Carter and all, but the fact of the matter is, until very recent times, the best place to insulate was against your own skin.
Kris De Decker of always wonderful Low Tech Magazine, looks at the issue of clothing as insulation and writes Insulation: first the body, then the home, We have talked about this anecdotally for years; Kris goes beyond the anecdote and shows us the math. Kris writes:
You could fill a library with reports and books describing the importance of energy-efficient heating systems and home insulation. However, not a word has been said or written about the energy savings potential of clothing, even though there has been a lot of progress in this area.
That's not entirely true; Carl Elefante has certainly written about it. He has noted that we let the the engineers take over and give us the modern thermostat era, with heating and air conditioning systems working almost all the time, summer and winter, to keep us in a three degree range around 70 to 73F. He complains that ASHRAE considers a human being to be "a six foot tall grey cylinder with a single data point," whereas a real human being can loosen his tie when it gets hot. Modern heating and cooling systems are passive; you set it and forget it. Elefante (and I) have been discussing systems that are active, where the people in the building participate by opening and closing windows, and adjust clothing to suit the conditions. Steve Mouzon also has made the point 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."
Terri Boake, University of Waterloo
Back in 1963, Victor Olgyay wrote Design with climate: a bioclimatic approach to architectural regionalism, which looked at the issue of personal comfort.
Olgyay also addressed Kris's issue that "nobody has published a research report on the evolution of the average room temperature in winter throughout recent history." That's because there really isn't one; temperature is only one factor affecting comfort. Olgyay shows that comfort is a function of temperature, humidity and air movement; humans are comfortable in a kidney-shaped zone that takes all three factors into consideration.
But again, we let the engineers take over and that kidney was reduced to a tiny little circle, requiring an almost constant input of energy. Over time, as Kris notes, the interior temperatures got warmer and warmer. Yet all of our efforts at insulating and sealing our homes pale compared to the savings that come from turning down the thermostat.
Note that the reduction in energy use for space heating thanks to more efficient homes was less than 20 percent from 1993 to 2005. Lowering the thermostat by 2° C (or 4°F) would thus result in energy reduction comparable to that. Turning down the thermostat from 22° to 18° C would initiate an energy savings of at least 35 percent.
His proposal: make clothing part of our energy saving strategy. It is much more efficient:
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 goes into the math, introducing the "clo", which "equals the thermal insulation required to keep a resting person (for instance, a couch potato) indefinitely comfortable at a temperature of 21° Celsius (70° Fahrenheit)." It is equal to .88R, or about a quarter inch of fiberglass insulation. Kris explains:
The clo is an interesting unit because it allows us to precisely calculate which clothes we have to wear to feel comfortable at any given indoor temperature. According to the "Encyclopedia of occupational health and safety", the required clo-value to maintain a neutral thermal sensation rises to about 2.7 at an indoor temperature of 10° Celsius (50°F). When the indoor temperature drops to 0° C (32°F), the required thermal insulation rises to 4 clo. As a rule of thumb, each change of 0.18 clo units compensates for a 1° C change in air temperature (according to the American Society of Heating, Refrigeration and Air-Conditioning Engineers - ASHREAE).
Not a new idea: Poster from World War II, Hennepin Library Collection
So now we can actually calculate the amount of clothing we need to feel comfortable in a lower temperature. Kris goes on to explain how thermal underwear and high-tech sports underwear can make a huge difference, perhaps almost replacing a home heating system. He concludes:
The energy savings potential of clothing is so large that it cannot be ignored - though in fact this is exactly what is happening now. This does not mean that home insulation and efficient heating systems should not be encouraged. All three paths should be pursued, but improving clothing insulation is obviously the cheapest, easiest and fastest way.
Read the whole thing at Low Tech Magazine
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More on putting on sweaters:
Eco-Tips: Jimmy Carter's Sweater
The Original Green By Steve Mouzon: A Must-Read If You Care About Sustainable Design