I'd like to cool one of my rooms with an ac but noise is a big limiting factor. Is it possible/feasible to put an ac in one room and somehow have it vent the cool air out into another room with a long hose? It's about 10-15 meters between the rooms. Would I need extra fans along the hose? Would moisture be an issue? Control circuits? Something else? I'm thinking of a dual hose portable ac since I live in an apartment with no place to mount an ac, so that seems like my best option.

EDIT: I'm not thinking of venting the hot air into another room in the apartment. I'm thinking of a two-hose portable ac unit, with both hoses out the window, and a third hose moving the now cold air into another room, so I can put the noisy ac unit far enough away that the noise doesn't reach me.

  • 2
    Sure, you could get some insulated flex duct, attach it to the A/C with a plastic bag and duct tape, and route it to the other room. Is it pretty? No. Will it work? Sure, as long as you don't care about aesthetics.
    – MonkeyZeus
    Jul 15, 2021 at 15:08
  • 10-15 meters is quite a bit: you might need to consider if the fans blowing the air will be capable to push the air through that distance, or if you will need additional fans, specifically made to push air along tubes (not every fan will do). You might need to calculate the pressure drop and compare it with the fan specs pressure-drop.com/Online-Calculator See also jay613 answer.
    – BlueCoder
    Jul 16, 2021 at 10:36

5 Answers 5


No. It will actually make your room hotter still.

Here is a technology briefer on portable A/Cs.

The deal-killer is that "one hose" thing. In your case, you're going to get it coming and going. You can only make this work if both the A/C and your passage are "two-hose".

Here's why that won't work as-is.

In the room with the one-hose A/C unit, the unit is ejecting hot air outside, via the one hose. That's how those units work. That air is being replaced by air being sucked in from anywhere possible - window leaks, door cracks, etc. And the air coming in is hot, wet outside air -- which defeats the purpose of air conditioning.

But it'll be worse with your setup. This vacuum on the A/C room will also draw air from your room. That will be replaced with hot, wet air from outside! In your room!

It's not just the heat. It's the humidity.

The biggest problem with "sucking hot/wet air from outside" is the wet. Humidity is just as important as temperature to your feeling of heat.

Now, stop and research the latent heat of vaporization. Removing humidity from air requires air conditioning - but all this air conditioning is poured into the latent heat of vaporization - turning water vapor into liquid water. This doesn't even cool the air (but it makes the air feel cooler because of lower humidity).

The upshot is that WET air coming in from outside is BAD NEWS. You need to minimize the amount of air being sucked in from outside, because you have to dehumidify it and that would steal a lot of your A/C capacity.

Two hoses - both places

The A/C unit makes some air hot, as you know. The air that it makes hot doesn't need to be air conditioned. Wet, hot outside air will work just fine for that. That's why two-hose portable air conditioners work just fine.

You need a 2-hose portable A/C (or hack your unit into being 2-hose) because if you use 1-hose, it'll suck hot wet air into your room, and that will defeat the entire purpose.

But also, when you pump air from the A/C room to your room, you need a 2-hose passage there too. You don't want conditioned air being pushed out of your room to ??? (because that's a waste) and then other air being sucked from ??? into the A/C room because that is likely to be more of that hot, wet air we don't want.

So that's it. Think 2-hose and it'll work. Take the default 1-hose and this won't work well enough to even bother.

  • 2
    Sorry, I was unclear. I was imagining a 3 hose setup. Two out the window for the ac unit, and one for putting the newly cooled air into another room Jul 15, 2021 at 17:28
  • @Filip Well the 2 hoses for the A/C is good, but. you really need a 4th hose for return air to your room, or else you'll be opening the loop and the make-up air will come from ????. You don't want air from ???? in your loop. Jul 15, 2021 at 17:40
  • Ironically a one-hose config on the hot side won't do as much harm if the unit is not in the room it is cooling. In fact, if the intermediate room is cooler than outside, it might do slightly better than a two-hose job. But two hoses to the cooled room is essential. And I don't think any portable A/C will do well through two 15 meter hoses. But there's one way to find out.
    – jay613
    Jul 15, 2021 at 18:33
  • 2
    "Wet" only matters in wet climates. If you're trying to air-condition a room in the desert, it doesn't really matter whether the air is 8% humidity or 10% humidity.
    – Mark
    Jul 16, 2021 at 1:06
  • 1
    Are these portable units reversible? I wonder if you could put it in another room (or outside), use your room as the vent, and then set it to heating.
    – user253751
    Jul 16, 2021 at 9:32

Yes it is possible. Assuming the AC is a portable unit in the long term it will heat your facility unless vented outside. If it does not vent outside in the long term it will heat your facility as it is only moving heat from one location to another plus adding adding its own heat mainly the heat of compression. Another consideration is it probably was not designed for this tube which in itself is not bad but it will cause a restriction in air flow. This will change the balance in the refrigeration system probably causing the condenser (the cold part) to build up with ice. This build up of ice will restrict the airflow even more eventually shutting down all cooling. However not all is bad, you could put a fan on one end of the tube and blow it into the other room with the inlet close to the AC, or the tube pointing at the fan, this will keep the proper airflow over the condenser (very important). I think this may be the easiest solution. The smoother the inside of the tube the better. Moisture should not be a problem as it should have a condensate tray with a way of removing the water.

  • A duct booster fan is what you are thinking of/want.
    – crip659
    Jul 15, 2021 at 15:27
  • That would work nicely!
    – Gil
    Jul 15, 2021 at 15:30

I do not think this will work well.

  1. Portable A/Cs are usually small and designed to cool one room. That room is expected to be somewhat isolated with doors and windows closed. A portable A/C cools by continually circulating that room's air through the A/C. Your portable A/C will have an air inflow and outflow. You will need to run TWO hoses to the other room, and ensure the other room is reasonably isolated so the air from that room circulates through the A/C. If you only run one hose, you'll be pushing air into the cooled room but sucking air in from the uncooled room, perhaps circulating it through the entire apartment. The A/C will not work well this way unless it is big enough to cool the entire apartment, in which case you don't need hoses, you just leave all the doors open and let it run. To cool one distant room you need two hoses. And also a third hose from the A/C to the outside for the hot air.
  2. The fan in a portable A/C is designed to produce flow, not pressure. Trying to run air through two 15 meter hoses will definitely require some "assistance" from additional fans designed for that purpose unless you use very big hoses, like half meter diameter. Getting all the fans to work together to produce good flow will be a science experiment.

Maybe if you install a window A/C in the desired room you can get used to the noise. Maybe you can install a quiet ceiling fan instead of an A/C.


Two hose portable unit would probably work if you can come up with an adequate adapter for connecting cold air discharge vent of unit to flex duct run to the desired cooling space. One thing I didn't see mentioned here is temperature control. The portable unit is going to cycle based on it's setpoint and the ambient temp in the space it's located. This could potentially result in over cooling of the space you're trying to condition if the spot where the unit is physically located is considerably warmer.


I'm using a portable AC in another room, and I get useful cooling just by setting up a fan to blow air from one room to the other - no duct, just increasing mixing. Whether this works well for you will depend on the layout of your rooms, of course, and the room with the AC will always be colder.

The advantage of this over your proposed hose setup is that it is not restricting airflow through the AC, which could make it less effective or damage it.

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