I have an outdoor building (327 sqft with tall ceilings) that I am using as a gym. It is basically 2x4s and plywood with a concrete floor. I want to put in an air conditioner for the summer months and I need some help/advice/opinions.

I was considering an in wall air conditioner, but they're expensive! So, I started looking into window air conditioners. I know they have the vents on the side, but seeing as the walls are just plywood, I thought it would be fine. I was going to install a platform for it to sit on.

There is a window in the wall between the gym and the garage. I don't know if I would be able to put it there instead of an external wall?

Is the external wall or the internal window a better choice? Will the window a/c work with a simple plywood wall? Is there a better way to do this? I've included a picture (pre-gym stuff moved in) to give a better picture of the room.


Editing to add some more info: I know that insulation would be ideal, but since I'm going to redo it, I'm not going to be spending the time/money doing that. I'm only going to be using the AC while I'm working out. It's more for humidity than for cooling. I know it's not the best situation, but I just need it to work for now


  • 3
    As it is now you want an AC to try to cool an oven. Insulation in the walls and ceiling will make an AC work much less, unless you use it in the middle of the night. A window is just a hole in a wall, so no problem making a hole for a window that is just the size for a window AC.
    – crip659
    Apr 11, 2022 at 13:39
  • 3
    Option 1 - Buy & install insulation. Option 2 - buy a huge air conditioner, and pay a lot of money to your electricity supplier.
    – Ecnerwal
    Apr 11, 2022 at 13:46
  • 1
    As noted, there's no requirement that a "window" have any amount of fixed or moving glass. Also, if you just set the AC unit on a platform, you'll get a cool breeze on one side and a very hot puddle of air on the other. Natural air circulation (cold air dropping, that hot air rising) will quickly mix the two and you'll end up with the same temp in the room as when you started with the added bonus of the extra money spent on your electric bill.
    – FreeMan
    Apr 11, 2022 at 15:31
  • If this is just "temporary", then go ahead and do whatever you want. Note, I put "temporary" in quotes on purpose - temporary installations have a bad habit of being far more permanent than ever intended...
    – FreeMan
    Apr 11, 2022 at 17:19

2 Answers 2


"window" of window air conditioner is because in a typical building that's the only way to install something that has both inside and outside. A hole cut in your external wall would work just as well, along with some support for the air conditioner as your plywood won't hold it by itself. Do NOT install in the window to the garage unless you want an incredibly hot and humid garage.

Seriously consider some insulation in your walls - it will significantly increase efficiency of any air conditioning (and heating in the winter).

  • Thanks - good point for the humidity in the garage. As I said, I'm hoping to get the whole thing redone, so I'm not going to be adding insulation at the moment. It's something I've considered
    – Brandy
    Apr 11, 2022 at 15:35


I agree with others that a window A/C won't help much on a hot day in this space. You should just install a couple of ceiling fans and keep those big doors open. This will beat A/C especially if you use this as a gym. You'll be sweating. The ceiling fans will help evaporate away your sweat. That's how A/Cs work! You'll feel cool, you'll use less electricity, this will actually work and will make less noise.

Who says a hole in the wall is not a window?

To answer the question, if the walls are just plywood, and you cut a hole in one of them, you effectively have a window! Who's to say it isn't? The added benefit is the "window" will be sized exactly for the A/C you buy so you won't need those crappy plastic louvers they all come with. Add a piece of nogging, oops, I mean a "window sill" above and below to support the A/C and you'll be in good shape, at least as far as the installation goes. You can even set the "window sills" to provide natural slope to the outside as you should.

  • The one drawback to this solution is that with those big doors open, the neighbors can see you working out. Not everyone works out to be an exhibitionist. Other than that, it's perfect! If that's a consideration, a mesh curtain across the door should help block the view while still allowing for plenty of air flow. It might also be desirable if bugs are a concern in this location.
    – FreeMan
    Apr 11, 2022 at 15:33
  • @jay613 - Unfortunately, a ceiling fan will not accomplish what I need. The biggest worry is humidity in the summer. I know it won't be perfect, but it just has to help alleviate it while I work out. A window sill is a good idea. I was just going to use one of those metal shelves on the outside. The sill would be good on the inside
    – Brandy
    Apr 11, 2022 at 15:37
  • 1
    @FreeMan - Lucikily, the big doors face the back of my house and it's far from the road. I currently open one of the doors on nice days.
    – Brandy
    Apr 11, 2022 at 15:38
  • 1
    @Brandy If you install a horizontal 2x4 block below the opening (and I'd suggest one above the opening, too), you shouldn't need anything supporting the outside of the AC. They're designed to be supported by the window sill itself.
    – FreeMan
    Apr 11, 2022 at 15:39
  • Well if you're going to go with the A/C ... it will hopefully at least keep the humidity down if not the temperature. Paint the outside walls a light color, especially any south-facing one, add insulation as suggested by others here, add some weather proofing around those doors and keep all the doors tightly closed.
    – jay613
    Apr 11, 2022 at 16:22

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.