Why does this house have 240V outlets in all rooms?
I have seen this several times in the PNW higher wattage plug in heaters used to be very cheap.  In this case they used portable heaters, not safe in my opinion but legal, if they had 15 or 20 am devices there are different types of receptacles that are legal for 220-240 devices dryer receptacles are 30 amp and would not be legal for smaller loads but a portable heater would be legal.