I have a small 950 sq ft single floor house, with a crawl space and force air heating. I have a portable Air Conditioner that has a large Intake and Exhuast tube.

The issue is that none of the windows in the house will work with the brackets it includes. The AC recommends sliding windows to use the brackets. My windows open up out at an angle, as it's an older home.

I do not have the money to upgrade the windows yet, but I noticed in the crawl space, there are barely any ducts for heat. It appears as though it just lets the heat rise.

My question is, can I put the Exhaust tube under the floor, and the Intake on the same floor, and still run this air conditioner? Or is it an absolute requirement to keep the exhuast and intake going outside? I do notice the exhaust gets very hot after about 15 minutes of running on AC mode.

  • There's nothing preventing it, other than a willingness to live with degraded performance. Modifying an existing window (e.g. replacing a glazed section with solid material plus the exhaust hose nozzel) might be a middle ground alternative depending on how well your aesthetic sensibility aligns with your construction craftsmanship. If the plan is to replace the windows anyway, that is an additional consideration.
    – user23752
    Jul 16, 2014 at 14:47

2 Answers 2


Air conditioning works by moving heat from inside the house, to the outside. If you dump the heat under the house, it will surely find its way back in.

  • Crap... where I live, temperatures fluctuate between -40 and +40c. I'll have to look for another method. Thanks Jul 16, 2014 at 2:22
  • Useful conversion mnemonic for us USA types: "30's hot, 20's not, 10 cool breezes, zero freezes." 40C is 104F. -40 turns out to be the same temperature in either system.
    – keshlam
    Jul 16, 2014 at 2:28

You could try running an insulated duct under the house to the side of the building (with appropriate provisions to keep rain and/or rodents from running into it). That might avoid/reduce having heat come right back up through the floorboards.

Remember that you also need to draw outside air INTO the hot side of the heat exchanger. If it draws from inside the house, that has to be made up with hot air drawn into the house from outside. So we're looking at two extended ducts, not one.

Personally, given that the portable ACs tend to be less efficient than the traditional boxes anyway, I'd suggest you consider a through-wall installation of the latter. (Or upgrade one window now so you can use an in-window unit), and do the others later.)

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