I smoke in my home office room which is 20x30 feet. I have a wall mounted 12000btu aircon in the wall, and want to put a window fan, one of those 10 inch high and as wide as the window with twin fans to suck some of the smoke out.
I vaguely remember getting lectured as a kid that running aircon with an open window is like trying to aircon the world. But I just can't remember what exactly the drawback is besides the room not being as cold as it can possibly be? Power bill increase or Damage to aircon or something toxic oozing out of the aircon?
I need to explain this to a non native english speaker who never lived around aircons and Googling for this answer only produces results for ceiling fans, since I guess everybody knows not to do it, so need to write about the reasons...
Thank you in advance.