According to "The Party's Over", USA EIA says that residences consume 21% of national energy. So I was wondering why we heat and cool people indirectly (by heating and cooling houses) instead of heating and cooling people directly (for example, through heated clothing)?
Now, I don't know of any such clothing (with a few exceptions, listed below). The reason we don't do this might be that there's no technology to do this, or that such clothing is uncomfortable or too bulky. But the reason might be that potential customers are happy with the status quo and don't want the stress of changing their habits. Or it could be that flaunting wealth is necessary to have status, and that living in an unheated house would be considered "poor". BTW, not all societies demand heated houses:
http://motherearthnews.com/library/1976 ... _Stay_Warm
To find out what's possible, I looked up the thermal conductivity (W/m°K) of various clothing-related materials:
aerogel .017 (but very expensive, see below)
air .024
wool .03-.04
cotton .04 (but cotton absorbs water, so .11 may be more realistic)
silk .04
felt .04
polyester .05 (but it feels "clammy" when wet unless a three-dimensional raised weave is used)
polypropylene .11 (but many web pages say PP is "best" for outdoors use because of it's water-repellance and comfort)
rubber .14
snow .16 (depends on compaction)
acrylic .2
nylon .25
fresh water .561-.679
concrete .9-2
iron 80.2
copper 401
silver 429
link 1 and
link 2 and
link 3 and
link 4
From the information I gathered, it appears that:
1) Right now, polypropylene is the best choice for low cost and lowest heat loss (especially when wet, and in extreme cold, like Antarctica). Wool and silk are also very good. Wearing long underwear made of any of these three materials allows you to comfortably reduce your home thermostat by about 10°F (5°C). But "cotton kills" if it gets wet (for example, from your own sweat) in cold weather.
link(excellent) and
link (Antarctica clothing) and
pdf (compares synthetic clothing fabrics)
2) Aerogel will probably become popular when it becomes cheaper. Apparently it traps air (like wearing clothing made of plastic bubble wrap?). I don't know if it allows sweat out.
"Toasty Feet" aerogel insole liners and
link
3) Insulating clothing keeps you warm by trapping a layer of air against your skin, meaning that the base layer must have a tight fit. But the tight fit is uncomfortable because it reduces your freedom of movement, especially in your arms. So maybe a more practical approach is heated clothing.
jacket heated by AA batteries and carbon fiber heating wire
4) Respiration causes evaporative cooling inside the lungs. The lower the humidity, the greater the evaporative cooling. "Heat exchange face masks" use copper (which has extremely high heat conductivity) to transfer around 80% of the heat and moisture from each outgoing breath to the next incoming breath.
link and
link
5) I didn't find any self-cooling clothing, but it does seem like there are a few possibilities:
* Metals have very high thermal conductivities (copper's is about 17,000 times greater than air's), so it would seem that bare skin touching any large metal object (wearing shorts and sitting on a metal folding chair?) would cool you down extremely quickly (if the metal temperature is lower than your body temperature).
* Loose cotton clothing is apparently much cooler than polypropylene because cotton does not move the sweat away from your skin until the sweat evaporates, which results in evaporative cooling. (Evaporation from liquid water to water vapor takes about 5 times the heat that heating water from just above freezing to just below boiling takes. If the sweat is touching your skin until it evaporates, then that much heat will be removed from your skin.)
link
Put on a hat, for pete's snake.
