"At rest, the human body gives off nearly 1,600 calories per minute.
During active periods, the thermal output jumps to about 2,900
calories per minute. In comparison, the human body gives off about as
much heat as a
100 watt light bulb. It's easy to understand,
therefore, why a room full of people grows warm just from the
accumulating body heat of everyone there".
G. Harry, "LIVING IN SPACE", p. 49. (
http://www.amazon.com/Living-Space-liHarry-G-Stine/dp/0871318415)