I have a multi-split level home with zoned heating (3 furnaces and air conditioners). The furnaces and water heater are located in an unfinished section of the basement. Oddly, the basement is warmer than the adjoining family room, or any other part of the house. What could be causing this? Thanks.

you don't say what type of heat you have, but I'll assume it is forced air.

The heat in the basement could be caused by the equipment itself, plus heat lost from any leaking or uninsulated ducts located within the space, and any uninsulated hot water piping.