What is the princiopal source of heating in many office bulidings in moderate climates?

Explanation

we know that organized energy (usable) degenerates into disorganized energy (non-usable). For example , when electricity is used for lighting bulbs in homes and offices, majorportion of electrical energy is converted into heat energy. Even the small part of energy that exists in the form of light, turns into heat energy. it is this heat energy, which is used to warm many office buildings in moderates climates. This explains why the lights in these buildings are kept on most of the time.
It si intersting to note that energy degenerated in the form of heat has no further use. The entire heat energy in a buliding cannot be refused to light even a single bulb and that too without some outside efforts.