Unvented Air Conditioners

Maintaining a cool climate indoors during the hot summer months comes at a price although some unvented air conditioners can cost less than larger, central heating and cooling systems. There are only certain types of cooler that fit that description so we'll take a look at them in this article.

We all know or are quite used to the kind of cooling system that keeps a whole house comfortable during summer and often we just turn it on, set it at the temperature we want and forget about it. It's not until a huge energy bill appears at the end of the accounting period that we smack our foreheads and wish we'd been a little more economic with our energy usage.

portacool portable evaporative coolerHowever, not so many of us are aware of the alternatives that exist. Some of them can actually be very frugal with the amount of energy they use, yet still manage to keep us cool on those really hot days and nights.

Evaporative Coolers

The most popular kind of low running cost cooler we have today is the portable evaporative cooler. It's sometimes referred to as a portable swamp cooler or even as a ventless portable air conditioner, although that last reference is not exactly correct.

An evaporative cooler is not an air conditioner at all, even though it looks a lot like one and produces cool air. It's what is going on under the hood that makes them very different beasts.

Where an AC employs a full refrigeration process to produce cold air, a swamp cooler uses only the power of evaporation. The difference in each process is huge, as is the difference in the amount of energy each respective process uses.

A typical refrigerant-based AC uses 2-3kW of electricity to keep a regular sized room cool, but a comparable output swamp cooler will only use 100-200w - less than 1/20th the energy consumption!


An AC requires a vent to be installed to allow the hot air it produces to be exhausted to the outside. That goes for portable units as well as fixed systems, reducing the portability aspect and introducing an ugly platic pipe into a room that is invariably dangled out a convenient window. This is necessary even in self-evaporating ACs as the hot, moist air produced by the units must be vented to the outside.

An evaporative cooler, on the other hand requires no vent. That's because it does not produce any hot air! The evaporation process simply uses a fan to blow air through a wet membrane which produces only cold, moist air.

That makes for truly ventless cooling that runs at a fraction of the cost of AC yet still provides enough cooling air to make a room comfortable in summer. You might be wondering at this point why everyone doesn't get rid of their costly and cumbersome ACs and switch to ventless, low cost evaporative cooling.

Beware Humidity!

There is one major downside to evaporating moisture to produce cold air. While it works fine when the ambient atmosphere is dry, the effectiveness of the process is severely reduced when the atmosphere become heavily moisture laden or saturated.

In areas of high relative humidity, it is simply not possible to put more cold moist air into already moisture saturated air, which is what happens when the humidity level reaches 100%. At that level, no cooling is produced simply because the air cannot absorb any more moisture.

That limits the areas that evaporative coolers can be used effectively in to only those that have naturally dry air, or humidity levels typically below 60%.

That's great if you live in a desert climate because the daytime air is usually very dry and so this kind of cooling is highly effective. It's not so great if you live in a coastal area or by a large expanse of water or in an area that gets high levels of rainfall.

Where there's a lot of moisture about, a goodly proportion of it will become absorbed into the air making further absorption more difficult. That's bad news for swamp coolers!

The bottom line is that if you want the advantages of ventless evaporating cooling devices, you should check the humidity levels in your area with your local weather station to make sure it is predominantly dry and not humid for most of the time. Also check out this handy resource at https://ventlessportableairconditioner.intervalinc.com that explains the process, its pros and cons at length, as well as this article about portable ACs to keep you up to speed.