Do You Need to Open Windows for Evaporative Cooling?

A common question that is asked about best usage practice for swamp coolers is: "Do you need to open windows for evaporative cooling to work effectively?"

This may sound counter-intuitive when people are used to running air conditioning with all windows and doors closed, but since evaporative coolers work differently, the ventilation needs are also different.

An evaporative air cooler, sometimes referred to as a vent free air conditioning unit needs to work as efficiently as possible, so where there are windows or other ventilation openings available, these should be kept open while running the swamp cooler.

Why Open Windows?

open window for evaporative coolerOpening windows allows the hot, moist air generated by the device to escape to the outside.

A handy tip for swamp cooler users is that it is best to open any windows or doors to the outside that are closest to the air cooler's vents.

If you have air conditioning vents in your rooms, make sure that the exhaust area of any open windows or doors is at least twice the size of the vent opening.

Evaporation levels will be lower when the air is humid or very moist. This reduces the cooling effect.

It may be helpful to turn the air cooler into "ventilation" mode, and then run the fan at a high speed. If none of these options work and your air cooler still doesn't seem to be working, it may be time for your cooler to be serviced.

Working Principle of Evaporative Cooling

It's important to know that evaporative cooling systems can be much cheaper to run than air conditioning devices.

This is due to the fact that they only use evaporation to cool the air, without any other mechanical operation.

This is in contrast to true air conditioners that use a refrigerant and refrigeration process, which uses a lot more energy. A cooling unit is located outside of the house and forms part of a duct-air conditioning system.

With swamp coolers, the cooling process uses an absorbent pad with water filtering through it from an internal tank.

The cooling pad is cooled by a fan inside the unit. The cooling pad can cool the air drawn in and distribute it throughout your home.

For more information about evaporative coolers and their pros and cons, please visit that page.

Benefits of Evaporative Coolers

An evaporative cooling system can offer many benefits for your home, for instance:

These cooling systems are so efficient that they will run at a fraction of the cost of standard ducted air conditioners.

Evaporative cooling is most effective when you have fresh air flowing through your windows. Evaporative cooling systems use the air that is passed through it to distribute cooler air throughout your home.

You can get the most out of your evaporative cooling system by leaving your windows partially opened. This allows warm air to escape and is being replaced with cooler air.

Your house will be filled with cleaner, fresher air because evaporative air conditioners recirculate air from the outside. This is in contrast to central air conditioning which recirculates the air throughout the house.

Evaporative cooling also has the advantage of being much less expensive to install and maintain than other types of air conditioners.

Disadvantages of Evaporative Coolers

There is really only one major drawback to running a swamp cooler during hot weather. That is when the air is very humid.

High humidity severely limits the amount of additional moisture the air can absorb and as evaporative coolers cool by evaporating moisture into the air, this severely reduces their cooling capacity.

At very high humidity levels approaching 100%, even the most powerful swamp cooler will be little more use than a big fan.

The thing to be aware of in this situation is the local climate and what the average humidity levels during hot weather are. If humidity is high in your area, an evaporative (swamp) cooler will not be an effective cooling solution.

In such a case, the only viable cooling option is traditional, refrigeration-based air conditioning.


While all air conditioning devices do require windows to be kept closed during operation to maintain a cool atmosphere inside and keep the heat out where it belongs, this is not the case for maintaining the effectiveness of evaporative coolers.

Since these coolers produce humidity, which is the very condition that hampers their cooling effectiveness, there needs to be a cross-draft to circulate the internal air and carry it away to the outside.

By opening windows, this air circulation is achieved simply and effectively.

This practice obviously brings up the associated question about whether opening windows will allow too much heat to get inside and render the cooling effect void.

In practice, this is not the case, as the cooler will continue to produce chilled air, keeping the indoor temperature lower than the outside air. Since energy consumption is very low, this is not considered to be such an important factor as it is with an "energy hog" air conditioning system.

So by all means, open some windows and enjoy the cool air produced by your swamp cooler, content in the knowledge that it is not making even the smallest dent in your household energy budget!

Posted: April 7, 2022

[Back to Top]