Does window AC take air from outside?

Does window AC take air from outside?

No, window ACs do not take air from outside. There is a partition in the middle of a window AC that separates outdoor air from indoor air. 

There’s a common misconception that window air conditioners are sucking air in from outdoors, cooling it, and then pumping it into your living room.

It’s an understandable thing to believe given the design of window air conditioners. We stick them in our windows with half the unit hanging outside. It’s reasonable to conclude that the window AC is at least exchanging air with the outdoors.

But actually, window ACs have a hard partition between the indoor side of the unit and the outdoor side with only a small refrigerant tube passing between them. Most air conditioners are dual-unit systems – an indoor unit absorbs heat from our home and an outdoor unit deposits it outside.

Window air conditioners are single-unit systems. That means they’re basically two-in-one designs with both an external unit and an internal unit attached together as one.

The indoor half of the window AC is tasked with absorbing heat. It does this by passing a tube of cold refrigerant through a long winding coil and circulating air over it. The heat in our home goes into the refrigerant and cold air blows out.

This now-warmer refrigerant passes into the outdoor component. A compressor then squeezes the refrigerant to make it much hotter. The fan in the external unit then blows outdoor air over the heated expansion coil and all that heat goes into the outdoor air.

At no point do the outdoor air and the inside air come into contact with each other.

However, there is an exception to this process. Some window air conditioners have a “fresh air” setting that intentionally pulls some outdoor air into the internal component of the unit. This is an option if you want a bit of fresh air without opening the window to let hot air in.