I need to install a window ac unit into a room without a window, so my idea is to vent into either the bathroom or the living room. I can't use the central AC at night (and there is no solution for this). So just accept this is the only solution left.

I can't move, which would solve the problem. I can't cut a large square hole in the wall to install a permanent window unit through the wall, because the outside wall is concrete and I am renting.

A mini split is too expensive and I'm not allowed to drill a hole in the wall anyway.

My room is a difficult room. This room has a sliding glass door which opens on the OUTSIDE, so I cannot just crack open the door to install a window or portable AC unit, or anyone can just walk in.

Here's the unusual sliding door instead of a window, no way to block it. It opens outside along the exterior wall, as shown.

enter image description here

So the idea is that I install a window unit inside of my interior doorway, and build a door frame to hold the window ac unit, so the door will open and close like a normal door. Or, I can just buy another same door for $50 and cut a hole in it to mount the AC unit.

The problem, then, comes with which room to vent it to, and how to do it.

If I vent into my bathroom, it will be easier to drain the ac directly into my sink, and I can leave on the vent fan all night to vent the heat and humidity. If needed I can also run a dehumidifier.

bathroom door location

If I vent into the living room, I could also install another window unit in the living room to vent the hot air from my room outside. I could also open both doors in the living room every morning to vent out the living room. And then run a tube from the window ac drain port across my room into my bathroom.

living room door location

Here is my layout, and my two proposed locations, in blue and purple:


As shown with the cubic feet, the living room is nearly 4 times larger than the bedroom. So, I'm thinking that may be the best solution.

Which door is a better location, and will this work?

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    The problem isn't (primarily) the condensate drain, it is the heat. For every drop of "cold" you put in your bedroom, you will add a corresponding drop of "hot" to another room. Unless you vent through one of the other windows. Have you considered something like this? The basic idea is you have a "window air conditioner" but instead of it sitting in a window where it can get air in, add heat from your room to Feb 22, 2022 at 19:17
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    I'm ok with heating the rest of the apartment during the 8 hours of night, then cooling it in the morning by opening the doors for air flow and using the central AC. I'm ok with increased electric costs. And I can mitigate it by putting another window AC unit over there in the living room window.
    – diy
    Feb 22, 2022 at 19:22
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    Option #3, bedroom exterior slider, hung in a piece of plywood and using blocking to secure the door.
    – Mazura
    Feb 22, 2022 at 19:25
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    how big is the kitchen window? You can get some pretty big A/C units that could handle the space, just add some fans to help circulate. I find that just having one A/C will reduce the humidity combined with a bedroom ceiling fan is enough to sleep comfortably.
    – rtaft
    Feb 22, 2022 at 19:30
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    It's not your question, but contemplate better ideas than having an A/C swinging on hinges on a makeshift door! How about putting the A/C on small casters, and attaching a door-sized piece of hard foam insulation? Then you just wheel the thing into the doorway at night. Or, heavy plastic sheeting with velcro to attach it to the door frame.
    – jay613
    Feb 22, 2022 at 20:41

1 Answer 1


I'll regard this as one of those (similar) situations where the room to be cooled is deep in the interior of a building, with no outside surfaces. That will avoid a lot of questions about where and how to install A/Cs.

The A/C has to be able to get heat to the outdoors or neither of your solutions will work. Over the course of eight hours, the living room cannot absorb and retain all the heat that the A/C will produce. It's not big enough. The heat has to go outside.

The bathroom idea might work well if the exhaust fan works, and if there is a way for fresh (outside) air to get INTO the bathroom. From your plan drawings it looks like the only opening is into the bedroom being cooled, so that really can't work. On the other hand if you could create air flow through the closet towards the kitchen, and open the kitchen window a little, the bathroom fan would draw in outside air from the kitchen window. If the exhaust fan is of sufficient size, and functioning well, that MIGHT be the better approach (of the two you propose) to removing heat from the bedroom and to the outside. The bathroom will hopefully remain 5 to 15 degrees above outside temperature all night, as its fan draws outside air through it.

The living room way might work. I think you'll have to experiment. Say it's 90F outside and also in the living room. Say you cool your bedroom to 75F. The temperature of the living room will start to rise, and once it gets above 95F or so the air conditioner's efficiency will reduce, and the effect of heating the living room will accelerate. This will eventually reach an equilibrium. The question is, where will that be? Will it be where your bedroom is 75, the living room is 100, and the kitchen window is expelling heat as fast as the A/C is producing it? Or will be be where your bedroom is 90 (producing nothing useful for you), the living room is 115? Is there any temperature, at least 1 degree below the outside temperature, where the kitchen window will remove heat as fast as it's being produced? Or will the living room temperature keep rising until the A/C fails completely?

I think the only way to find out is to try it. I think the equilibrium state will happen within an hour or two.

It's possible that putting a second A/C in the kitchen window will expel heat faster than if you just leave it open. That's worth trying if you have a second A/C. It's also possible that putting the largest A/C you can squeeze into the kitchen window and leaving the bedroom door open will, on the whole, produce the best cooling effect, even if it's not that great.

  • Closet only opens into the room, it's a walk-in closet. It doesn't open into bathroom or living room.
    – diy
    Feb 22, 2022 at 20:11
  • Closet only opens into the room, it's a walk-in closet. It doesn't open into bathroom or living room. House will be 69 degrees at night right before bed. Then, the bedroom needs to maintain 69 degrees for 8 hours at night. During summer, it could get to 70s/80s during the night in summer. It's 60s at night this time of year ("winter"). It will never have to cool from 90s/100s. It doesn't get that hot at night here.
    – diy
    Feb 22, 2022 at 20:18
  • I think you're right when you say I'll need to experiment. Just hoping for any more tips before I move forward. This did help because now I know I need two window units, not one. One of them has to go in the living room window.
    – diy
    Feb 22, 2022 at 20:21
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    I used 90 in my illustration intentionally, because window A/Cs become less efficient above 95. If you can find that "equilibrium" while keeping your LR well below 95, this might come together.
    – jay613
    Feb 22, 2022 at 20:33
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    Exactly that. You could also set your central A/C to 95 as an escape hatch to keep things from spiraling .. unless the thermostat is in the bedroom.
    – jay613
    Feb 22, 2022 at 20:36

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