Good day! I have a 2.4 HP window type air conditioner that instead of opening to the outside world, opens into a small 3x4x5 ft space with a screen on the opposite end. The space gets really hot when the aircon is running and I'm afraid it is affecting the aircon's efficiency. I am renting the unit so any major construction changes is out of the question. Would putting an exhaust fan on the other end help? Hope you can help me out. Thanks in advance.

Why are you concerned about the heat is it feeding back into the building? I have seen this sort of thing done you might want to see what is happening to the waste water or you might have a mold problem. I'm assuming the building owner installed this unit so you should discuss your concerns with him or the rental agent