Efficency of electrical heat and light

[hollis]

We are having a disagreement about the fact I maintain that in an electrically heated home, during the winter months you may as well leave lights on if you want to because the energy from the lights will contribute to the total heat of the room the same as electrical resistive heaters. Ie, if a vessel (home/room) would need say 2000 w of elect heaters on to maintain 70 degrees. I say you would get the same amt of heat from 10- 200 watt bulbs,.or a hundred 20 watt florescent ones,.. 4-500w clothes irons or a 2000W motor. My partner says that in the case of the bulbs that the light energy is lost but I will guess that and light (or more infrared emissions) hit objects in the room, walls etc and heat it up to the same amt as anything else. I know some elderly people that live a rather dark,molelike existence by turning off most lights to "save money" in their all electric homes. Same with some people with S.A.D. that could use the extra light.
If that's the case could you not also keep some of the heat costs down by coating the inside of exterior or less heated walls with coatings that reflect radiant energy back into the room slowing down its loss to the outside? I understand that there are some new paints that are light colored but look pretty conventional that reflect a fair amt of IF radiant energy.

 

[chroot]

hollis,

Your instinct is correct -- incandescent light bulbs are actually more effective at producing heat than light. In a perfectly insulated house, a string of light bulbs would be just as effective as central heating.

In a real, imperfectly insulated house, the rate of heat transfer across the insulation depends on the temperature gradiant across the insulation. Loosely speaking, if you put all the heat in one spot (say, the ceiling above a lamp), you'll lose more of it through the insulation than you would if the same heat were distributed uniformly through the volume of the house.

- Warren