Why Air Conditioners Vent to the Outside

One of the things that many people don't know about air conditioning is that it produces hot air that needs to be vented outside the building for the system to work most efficiently and keep the interior cool.

It surprises people to discover this, as most fixed units look like they are just attached to the wall with no visible ducting.

However, the truth is that all true air conditioners really do produce a lot of hot air. Often they produce more heat than the cold air that keeps us all nice and cool in our homes during the heat of summer.

For those just discovering this amazing little nugget of knowledge, I have created this short article to explain why AC needs to be vented and how it is accomplished.

A Lot of Hot Air

portable air conditioner window vent kitThe process that produces that lovely chilled breeze emanating from the AC unit incorporates a refrigeration system that is in many ways like any domestic refrigerator, just bigger.

A special gas that rapidly cools when compressed is used as the heart of the system and it is this chilled gas that cools the air for our enjoyment and comfort.

To compress the gas, a heavy duty compressor unit is put into service. But just like all mechanical devices, this compressor produces heat as a by-product of the work it has to do. The bigger the compressor, the more heat is created.

That's why you only notice a little heat coming up from the back of your fridge in the kitchen. The fridge's compressor is relatively small because it only has to produce enough "cold" to keep the small interior of the fridge at the right temperature, so it only produces a small amount of heat.

An air conditioner has to cool a very large volume of air by comparison - the entire cubic volume of atmosphere in a room! That takes a pretty big compressor which in turn produces an awful lot of heat.

Thankfully, that excess heat is easily taken care of by pumping it out the back of the AC unit, through a pipe in the wall to the external unit which acts as a condenser and extractor all in one. It extracts the hot air and blows it out into the outside atmosphere and condenses the excess moisture created by the refrigeration process, allowing it to also escape to the outside.

Portable AC Vent Hose

While central or fixed mini-split AC uses concealed ducting or other exhaust methods to deal with the unwanted heat from the compressor, portable units don't have the ability to do this.

They must get rid of the heat they produce and putting the flexible plastic vent hose pipe through an open window is usually the most popular way.

What About Portable Ventless AC

You often hear about the mythical beast known to many as a vent free portable air conditioner, but sadly, such a thing does not really exist.

Even with an advanced, current technology and engineering behind it, free standing climate cooling appliances still produce hot air that must be taken out of the building via some form of vent or exhaust ducting.

While fixed units can do this quite covertly, by sending the exhaust through a pipe installed through the wall directly behind it, effectively hiding it from human eyes, portable units are dogged by the highly visible and unsightly vent hose pipe that protrudes from the rear of the unit and is either connected to a window venting kit or unceremoniously dangled out of a slightly open window.

To be honest, that was exactly how I did it during my student days as I couldn't afford the extra cost of a window kit. I just opened the window, pushed the end of the pipe through and stuffed old sweaters and cushions into the gap to stop the hot air from coming back into the room!

The only truly ventless air cooler appliance is not real air conditioning at all, but an evaporative or "swamp" cooler. This kind of device doesn't have a refrigeration process and so does not produce any heat. That means no ugly vent hose!

There are limitations to swamp coolers as I will describe them in their own article that you can read by following that link. Or visit ventlessportableairconditioner.intervalinc.com for more information.


So for those that need a way to stay cool during the summer and it has to be AC, be aware that it must be vented to the outside to exhaust the hot air out of the building, whether you have a fixed system or a portable unit.

They all have their place and to some people are an absolute necessity regardless of the downside of having to put up with an ugly plastic hose hanging out a window or paying the extra to have a fixed system installed.


Posted on Sep 7, 2018