Should you keep windows open with evaporative cooling? – Air Conditioning Perth

Yes, you usually need to keep some windows open with evaporative cooling. Unlike refrigerated air conditioning, an evaporative system draws fresh air into your home continuously, so that air needs a way out. Dacs Air Conditioning & Electrical helps Perth homeowners understand this essential difference: closing everything can restrict airflow and leave rooms feeling uncomfortable. Purpose-designed relief vents can provide an alternative exhaust path in some installations.

As Perth’s spring weather warms up, it is a good time to check how you operate your system before summer arrives. The right window arrangement helps cooled air travel through the rooms you use.

Keep suitable windows or external doors partly open while your evaporative cooler runs, unless your installation has an approved alternative exhaust arrangement. Follow your model’s ventilation instructions, distribute openings across occupied rooms, and keep airflow paths clear. Closing the house as you would for reverse cycle cooling can reduce comfort.

Why does evaporative cooling need an escape path?

An evaporative cooler uses a fan to draw outdoor air through water-soaked cooling pads. Evaporation cools that air before it travels through ducts into your home.

The incoming air then needs to pass through the living space and escape outside. Think of the system as a continuous flow rather than a sealed circuit.

A window opening is therefore part of the cooling arrangement. It gives incoming air somewhere to go, helping it move through the room instead of meeting a restricted exit.

This explains why habits that work with a split system do not necessarily work with an evaporative cooler. Before changing windows or controller settings, identify which type of cooling you are using.

How far should you open the windows?

There is no universal window gap suitable for every home. The required opening depends on the system, airflow, room layout and manufacturer’s instructions.

Start with the guidance for your particular model and speak with Dac’s team to get the best advice and guidance.

This is why advice such as “open every window five centimetres” can be misleading. A small sliding-window gap and a partly opened large door provide very different exhaust areas.

If you cannot find the manual, ask your installer or service technician to explain the required ventilation for your home. Once you know the intended arrangement, you can operate the system consistently instead of guessing each time the weather changes.

Which windows should you open?

Choose openings that help air travel across the room before leaving the building.

Manufacturer guidance recommends opening windows or doors farther from the cooling outlet where possible. An opening immediately beside an outlet may give air a short route outside rather than encouraging it to move through the occupied space.

Look at each room as an airflow path:

• Where does cooled air enter?
• Where can it leave?
• Is a closed internal door interrupting that route?
• Does the arrangement serve the rooms you actually use?

Avoid assuming one open door near the kitchen will provide the best ventilation for every bedroom. Different layouts need different arrangements.

Evaporative cooling versus reverse cycle: should windows be open?

The operating difference is straightforward.

If your home has both types, make sure everyone knows which system is running. The window arrangement should match the cooling equipment in use.

Not sure? Speak to the team at Dacs to find out what is best for you to get the best value of out your air conditioner.

How to check your window arrangement step by step

Use this practical checklist before deciding your cooler needs repair.

1. Confirm the system type. Check that you are operating evaporative cooling rather than refrigerated air conditioning.
2. Read the ventilation instructions. Use the manual for your installed model as the starting point.
3. Provide suitable exhaust openings. Arrange windows or external doors according to those instructions.
4. Check internal airflow paths. Where air must travel through a doorway to reach an external opening, keep that route clear.
5. Confirm the operating mode. Cooling mode and ventilation-only mode serve different purposes. Check your controller’s instructions.
6. Record what you notice. Note whether every room is uncomfortable or whether the problem affects only one area.

Change one thing at a time. Adjusting several windows, doors and controller settings together makes it harder to understand which change helped.

These checks also give a technician useful information if the problem continues.

Why can the house still feel muggy?

Window position is only one part of evaporative cooling performance.

Evaporative systems depend on outdoor conditions. Humid weather can limit the temperature reduction they achieve, even when the equipment is operating correctly. Restricted exhaust openings can also make it harder to remove moist air from the house.

Opening more windows is therefore not a guaranteed solution to every uncomfortable afternoon. First check the intended ventilation arrangement, then consider the weather and controller settings.

When contacting Dacs, describe the symptoms clearly: whether airflow feels weak, whether the air feels cool at the outlets, and whether discomfort affects the whole house. Those observations help guide the assessment.

Can you close the windows overnight?

If the evaporative cooler remains running, it still needs its intended exhaust path.

Do not assume night-time operation removes the need for ventilation. Some installations have purpose-designed relief arrangements that allow operation with windows closed, but you should confirm whether your system has that provision.

Security matters when choosing openings. If you cannot provide suitable ventilation securely, ask about an appropriate solution for your installation rather than running the cooler in a sealed house.

Once the cooler is switched off, windows can be closed as normal.

When should you ask Dacs to check the system?

Arrange an assessment if comfort remains poor after checking the operating instructions and ventilation arrangement, particularly if performance has changed noticeably.

Prepare a short description of the issue, your controller settings and any displayed fault code. Leave rooftop inspection and component checks to a qualified technician.

For Perth metro homeowners, Dacs can help assess the system and explain the next step. Learn more about Dacs’ evaporative cooling services or call (08) 9313 4645.

Frequently asked questions

Do all windows need to be open with evaporative cooling?

No. You need sufficient, suitably positioned exhaust openings, rather than every window fully open. Follow the ventilation instructions for your model and provide airflow paths through the rooms being cooled.

Can I use an open door instead of a window?

Yes, an external door can provide an exhaust opening if its position and opening area suit the installation. An internal door alone does not let air escape outdoors.

Does opening windows waste the cooled air?

For evaporative cooling, exhausting air is part of normal operation. The system continuously supplies fresh air, which must pass through the home and leave through suitable openings.

Why is one bedroom warmer than the others?

Possible causes include an unsuitable exhaust opening, a restricted airflow path or an issue with the outlet or ductwork. Check the room’s ventilation arrangement first, then arrange an assessment if the problem continues.

Can evaporative cooling run with every window closed?

Only where the installation has a suitable alternative exhaust arrangement, such as purpose-designed relief vents. Without an approved exhaust path, closing every window and external door can restrict airflow.