How to do heating in triplex with basement, 1st floor, 2nd floor

[David McCracken]

Hi BP,

I own an upper/lower duplex. I'm converting it into a triplex by finishing part of the basement into a studio flat. The basement flat is a small space, only about 300 sqft. There is one furnace so the heating is shared. The previous owner set up the thermostat in the common area of the basement.

Now I'll have three flats all with shared heating and one thermostat. In the winter, the temperature is going to vary greatly between the basement and second floor flats. What's the best way to ensure the tenants aren't constantly fighting over the thermostat? Should I make the new basement studio completely electric heat? Should I write in the studio flat's new lease the thermostat must be kept at a comfortable temperature for all building occupants, and recommend them by a space heater to cover any temperature difference?

Any help is greatly appreciated!