Is It Bad to Leave My Windows Open When the Is AC On?

In a word: YES!

In fact, this is the worst thing to do when you are running your air conditioning. The reason: you are essentially un-conditioning the house while the air conditioning system is simultaneously trying to do its job, which is to improve the home’s indoor air quality—and your comfort—by lowering humidity levels and adding cooler air.

How air conditioning works
The primary functions of an air conditioner, which make up the conditioning process, are to cool, dehumidify, and filter the air within your home. The central AC does this by absorbing the heat and moisture indoors and transferring them to the outdoors.

How this works:

• The warm indoor air gets absorbed by the system’s air handler as it blows over its (cold) internal refrigerant coils.
• The liquid refrigerant turns the warm indoor air into a gas, which is then pumped to the outdoor condenser coils and released into the outside air. Essentially, the heat is pulled out of the house and sent outdoors.
• Further conditioning occurs when the unit extracts excess moisture from the air as condensation forms on cold evaporator coils. This prevents the home’s air from feeling clammy—that damp, sticky feeling in the environment.
• Airborne particles such as dust, pollen, and other allergens pass through the system’s filter, trapping them there so that the circulated conditioned air is not only cooler, but also cleaner.

The result is newly chilled, conditioned air that is circulated through the house in a continuous loop, based on the thermostat’s set temperature.

Why it is bad to leave windows open when the AC is running
Doing this sabotages the hard work your AC system is doing to keep your house comfortable, and will run up your energy usage and expenses. Your system will use more electricity than it typically needs because it ends up running constantly or more frequently than usual.

Plus, the system can take 24-48 hours to effectively re-condition a house to comfortable levels if windows are left open, making that inefficient and costly. Compounding the problem is that when people open windows in certain rooms, they often forget to close at least one of them (we’ve all done it!). This leads to unnecessary service calls because the central air conditioner is being overtaxed needlessly. Continuous running overheats the compressor, which shortens the lifespan of your unit.

We advise that if you want fresh air during air conditioning season, install an energy recovery ventilator (ERV system), a whole-home solution integrated with your HVAC system that will bring in fresh conditioned air and exhaust stale air. If you are replacing your existing central air conditioner or are installing a new HVAC system, ask us about connecting an ERV to your equipment.

Other options are to turn off the AC completely and then open the windows to let in the natural breeze and fresh air, and run a ceiling fan or box fan to circulate the air.

Looking to stay cool this summer? Contact Bloomfield Cooling, Heating & Electric.
Whether you experience an AC breakdown and need service, want to replace your outdated central air conditioner, or need information about installing a new HVAC system, the team at Bloomfield Cooling, Heating & Electric is here to help. Contact our office at 973-237-0505 or fill out the form on our website to schedule a consultation.