My bedroom gets ridiculously hot and I taped tin foil over the window. It didn't help much. I'm thinking of getting an air conditioner but the ledge on the window is small and the window doesn't open very much. I was looking at the portable air conditioners on Amazon and wonder, how do they work? Does the hot air get ejected through a hose that I could put out the window?

My window opens like this one so I take it a window AC is out of the question? outside opening window

  • Based on the update with the picture, the only way you could put a window unit in this window is to remove the window first. Oct 3, 2012 at 20:25

4 Answers 4


Often the actual pane unit for awning and casement windows can be removed (especially in newer and higher end windows). If this is the case, you can install a standard window air conditioner.

You would use an "L" shaped bar, called angle "iron" or angle stock (actually aluminum is probably more convenient), placed at the top of the unit instead of the upper sash to hold the unit in the frame.

angle stock

The flat inside face of the angle iron would overlap and be screwed into the frame at the edges. The horizontal edge of the angle would be trimmed to fit inside the frame.

The air conditioner can be centered in the gap and the AC units side filler panels can be used to cover the gap. In the alternative, filler panels (clear plexi or any other thin weatherproof material) can be cut to fill the rectangular gaps on either side of the unit in place of the AC unit's fillers, which usually do not seal too well. In the alternative, the unit can be centered and one panel used to fill the gap. Be sure to seal around the AC edges and around the panels in either case.

Because most awning windows are not too tall, you may need a low profile AC unit such as this one

low ac


Window unit air conditioners rely less on the ledge and more on the window itself to keep from falling. The unit is surrounded by a frame. You carefully set the unit in the window with the frame tilted forward some towards you. You then lower the window until the A/C frame can rest on the frame of the window itself.

Portable air conditioners usually (as I understand it) have an exhaust hose that you use to vent the hot air outside. You could put this hose out the window - but you'll want to make sure the rest of the opening is blocked off so as to not allow outside air back in while you're pumping out the hot air.

  • Most portable A/Cs have outside air intake and exhaust. Outside is taken in, run across the hot condenser coils, then expelled. This is to avoid wasting cool indoor air to expel heat. Some portable A/Cs have two separate air hoses, others may have the intake and exhaust chambers packaged into one hose. Oct 3, 2012 at 20:08

Portable A/C units send warm air outside through a hose (typically a 4" or larger hose, similar to a dryer), and also produce water as a result of condensation that has to be dealt with. There may be a hose for the water that has to go to a drain (or outside), and some units have a reservoir for the water which must be drained periodically.

Portable or not, A/C units can use a fair amount of power, so you may need a dedicated circuit. Check the specifications, it should indicate the current draw and typically the higher the BTU (cooling power), the higher the current draw. Make sure if you're adding this to an existing circuit that already has stuff plugged in, that you don't exceed the maximum draw (typically 15A). This may mean you're limited in how big a unit you can buy, so don't just rush out and buy the highest BTU unit you can find.

There are also single- and dual-hose units.

  • Single hose units use the air inside the room to cool the unit as well, and exhaust some of this air out of the hose. This means some of your cooled air is being sent outside, and also that there is negative air pressure in the room, which means air will be drawn in under doors and through vents to replace it. If the air being drawn into the room is hot, it'll make the room hotter.
  • Dual hose units have two hoses, one to take air in and one for exhaust. They use outside air to cool the compressor, and have a completely separate system for the cold air in the room. No outside air mixes with inside air, and you don't get any pressure change in the room. Since these units are using warm air to cool themselves, they're slightly less efficient theoretically than the single-hose units, but because they're not creating negative air pressure, they may actually make the room feel cooler.

Here's an idea for a temporary installation:

  1. Open the awning as far as possible and latch it to keep it open.
  2. Set up the small portable AC unit as usual (with side wings).
  3. Screw a 1" x 2" board across the window where the top of the unit will be (in the same place where the window would normally hold it).
  4. Install the unit, and fill in the gap above unit with plywood, Plexiglas, or whatever you've got.

It might look kind of funky but who cares if you are dying from heat!

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