Fridge question

In a physics lesson at school we were asked whether a working fridge with the door open in a sealed room would increase, decrease or not change the temperature of the room. I answered that it wouldn't change but the teacher told me that it would increase.

I now think I was -  if not right, exactly - not wrong anyway.

If this experiment is taking place in an idealised universe then there is no reason that the fridge cannot be 100% efficient and therefore it will cool by exactly the amount it heats. In which case I would be right, there would be no change in temperature in the sealed room.

The teacher was treating this as a real life fridge which would then be less than 100% efficient and would produce more heat than cooling. But if this is the case then there is no such thing as a perfectly sealed room either. Some of the heat gain will be dissipated through the walls even if they are insulated. How much is unknown and could be less than or more than the amount generated by the fridge. So the answer is unknown in this situation.

So the answer is: either no effect or any of the options.

So there.