My fathers parents lived in a mill house with the large grate in the middle of the first floor allowing the heat from the hand fired coal furnace to come up to the 1st floor. On the dining room wall there was a small ornate cast iron pointer with cool --- warm embossed letters on the housing, two small chains from this control went to the basement and operated the air damper below the grates to control heat output. On the 2nd floor all the bed rooms had cast iron grates in the floor that opened to the dining room and living room below, my father and aunts regulated the room heat with these. In the kitchen was a coal fired range with water heating coils and a 30 gallon copper water tank for hot water, the kitchen range was converted to kerosene when I was in 2nd or 3rd grade (early 50's). As typical there was a wood framed coal bunker in the basement near the hot air furnace, I think there was a primitive humidifier in the furnace air plenum, can remember my grandfather adding water to the top of the furnace.