It seems like the best place to install the 12,000 BTU air conditioner in our house is in a window in the living room. On the other side of that window is an enclosed porch, approx 27x7 feet. Because the windows jut out into the room, there would be about 4-5 feet between the end of the AC and a window. Here's a diagram of the house. The porch is the lower part and the red is where the AC will go enter image description here

The online consensus seems to be that installing a window AC between two rooms like this is bad news but I'm wondering if it might be more useful in this situation since the porch has some airflow and the unit would be relatively close to a window. I have two main concerns: airflow and drainage.

Drainage seems relatively easy, as I could hook a hose up to the bottom of the unit and run the water right out a window.

Airflow seems the larger issue. Even though it's almost entirely windows, would the porch heat up so fast that it would ruin efficiency (and maybe the AC unit condenser)? And if that's the case, could I try to run a duct from the back of the AC to the window about four feet away? Would that make it feasible or should I just find another window?

Your thoughts? Thank you!

  • 1
    A window unit is cheap, but exhausting onto a closed porch would make the porch unbearably hot, humid, and noisy. Look at low end mini-split a/c units that can run on 120 V, are quiet, can fit in a wall requiring only a 3 inch diameter hole between the air handler inside and the condensing unit outside. This hole is for the refrigerant lines, power, and condensate drain. Jun 11, 2017 at 21:59
  • 1
    I believe you would definitely have to have a duct going from the condenser coils output to the window. The water could be carried outside in tubing, but the whole thing would still be noisy and would make the porch a very unpleasant space to be in. Jun 11, 2017 at 22:08
  • That might work for us, @JimStewart as we never go out there. It's basically a room for junk. I will look into a mini-split system regardless but not sure we're in a position to buy new right now. If we set up a duct, would I do it from the very end of the AC unit to the window so air still flows through the vents on the side of the unit, or should the duct basically go from window all the way to window? Jun 11, 2017 at 22:27
  • I believe that air flows into the unit through the side vents, or at least through one of the side vents, then out the back and maybe out the other side too. Note that the air flow paths inside and outside are completely separate from each other. The hot air flowing out the back came from outside through one (or both?) of the outside side vents. On the inside air flows into the unit (usually at the bottom), passes over the cold evaporator coils, and then back into the room (usually at the top). Jun 12, 2017 at 9:11

2 Answers 2


If you have a forced air furnace for heating, you could install the window unit in another window and run the furnace fan to circulate the conditioned air throughout the house. My son did this in his first house. As for using the window you mentioned, you could do it your way if you can insure good air flow in and out of the porch area to keep that area the same temperature as the outside. Window fan/fans, may be needed. If the porch area heats and has high humidity that will affect the operation of the A/C unit and could ruin the porch area. All window A/C units produce lots of heat and humidity when operating. So you will have to make sure you address these issues. A split system or other type of cooling unit would be preferred. Depending on where you live a 12,000 BTU unit may be a little undersized.


If we set up a duct, would I do it from the very end of the AC unit to the window so air still flows through the vents on the side of the unit . . .?

I would say yes. And open windows near the sides, i.e., away from where the heated a/c air goes out the window.

  • I've seen a throogh window air-con installed in an interior room with ducting carring the hot exhaust across two offices to the exterior of the building, the drain went into a sink. its purpose was to a small computer room cool, so the noise wasn't a problem.
    – Jasen
    Nov 24, 2018 at 5:06

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.