Sunday, December 26, 2010

Temperature oddity (updated)

Does anybody else have the experience that even when the room temperature is the same, you still feel colder when it's frost outside?
Physically, I mean. Very odd, I think.

Update:
I think I got it!
TCGirl found this...
"Believe it or not, your body and all other objects are always giving off or absorbing heat by radiation. Heat transfer by radiation goes from a hotter object to a cooler object - like from the sun to earth, or from hot coals to you, or from your body to the cold walls of a lonely castle on a dark and stormy night."

Doesn't quite explain it, but I realized: the thermometers, unlike a body, are probably only reading the air temperature.
The other source of heat which we normally don't think about is radiation heat. From the walls! In warm weather, it's considerable, in frost it goes away, and this might well make it a lot harder to keep a good body temperature.

Which says to me that a building in a cold climate really should be very well insulated all around, otherwise you might never be really comfortable. I don't think higher air temperature is a good substitution for all that radiation, it warms the body in a very different way. (Not sure how, yet.)

Ray said:
One trick I use is to have a fan circulating the air, just to make sure that the heat is distributed evenly. Sometimes, that can make a difference, because without that, the heat may be going up the walls toward the ceiling without warming central parts of the rooms. Seems to work for me.

Update:
A said:
There is a scale called the Bedford Comfort index which takes account of air temperature, humidity, radiant temperature of surrounding etc to come up with an index. I was able to demonstrate to a class of students that their subjective estimate of comfort within a classroom matched pretty well with values using this scale from appropriate measurements.


Well, there you are then, thank you. Interesting.

8 comments:

Bruce W said...

I have been told that there is scientific support for this. As the outside temperature goes down, your home loses heat faster than at higher temperature, and your body detects this increased rate of heat loss. Even with the heat in your home on, it is still flowing out faster, and the loss makes you feel colder.

Sounds reasonable to me.

eolake said...

Mmmyeah, I'm not sure. Unless we attribute perceptions reaching out many meters from the body (which might be true), I don't know how the body would sense that the house is loosing heat if the room temp is the same.

...........................Ray said...

Maybe when you see evidence of colder temperatures, your brain sets you up to become warmer by convincing you that you are cold.

Another factor is less indirect - when did you last restore your body's heat source with a meal?
Sometimes, if it has been several hours since I had a good meal, I'll feel cold even when the thermometer says I should not be.

eolake said...

Yes!
I've only discovered this after some psycho-somatic change or other made me loose the snacking-addiction, some time in 2009. Before that, I never got actually hungry, because I snacked all the time.

TC [Girl] said...

I think that, unless a building is well-insulated and the windows are "dual-glazed" (at least; they make triple glaze as well!), the heat just moves out of the building faster than when the temperatures outside are closer to those inside.

eolake said...

(Post updated.)

Anonymous said...

There is a scale called the Bedford Comfort index which takes account of air temperature, humidity, radiant temperature of surrounding etc to come up with an index. I was able to demonstrate to a class of students that their subjective estimate of comfort within a classroom matched pretty well with values using this scale from appropriate measurements.

eolake said...

Wow, thanks. I knew there had to be something to this.