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Is it bad to leave windows open while the AC is on?

Unless you want sky-high cooling bills, it is a bad idea to leave windows open during the summer in Phoenix. Air conditioners work best by cooling air in confined spaces, and open windows either let cool, conditioned air drift outside or bring in hot air from the outdoors.

The only exception to the practice of opening a window with the A/C running is when it’s considerably cooler outside than in, as long as the air isn’t overly humid.

Leaving the air conditioner on while the windows are open just after a monsoon storm may seem like a good idea. In reality, though, it will increase the amount of work your A/C has to do. The extra humidity the fresh air brings in will eventually make your air conditioner work harder once your home warms up again.

Temperature Isn’t Everything

One of the reasons a Phoenix summer is tolerable is that it’s mostly a dry heat. You may have seen homes or businesses with evaporative coolers that use flowing water and large fans to cool the interiors. They must leave windows open for the incoming air to exit. The coolers work well until the humidity increases, at which time they become ineffective. The humidity during the monsoon is why so many homes in the valley use central air conditioners instead.

When you leave windows open during the monsoon, you’re pulling in humid air that the A/C will have to remove. It’s impossible to stop the dehumidification process that occurs with air conditioners. When air hits the evaporator coil inside the air handler, the moisture in it condenses on the coil and drains away. When the air is dry, the cold refrigerant in the coil absorbs interior heat faster. It’s this loss of heat in the air that cools your home.

Other Unwanted Side Effects

When you leave windows open, more dust enters. Your air filter may not be capable of trapping the smallest dust particles that will enter the air handler. Dust will coat its exposed parts, like the evaporator coil, electronic components, the fan motor and the ductwork.

Dust acts as insulation in the air handler and too much can cause premature breakdowns and higher energy bills. When it covers the evaporator coil, it slows the cooling process. Dirty filters reduce the airflow through the air handler, which forces the air conditioner to run longer. Couple a dusty evaporator coil with a clogged air filter, and there’s a possibility the coil will freeze over, which has the potential to burn out the compressor.

Alternatives to Open Windows

The HVAC industry has developed an energy efficient solution for people who like to leave windows open in the summer. Energy or heat recovery ventilators (ERVs or HRVs) provide balanced ventilation by pulling out as much stale indoor air as they pull in fresh. Each HRV or ERV uses heat exchange technology that removes the energy from the outgoing air and puts it into the incoming air. While they do use some electricity, it’s far less than when you leave windows open to improve air quality.

It’s also helpful to have Forrest Anderson inspect your cooling system at least once during the summer. As hard as heat pumps and air conditioners work in Phoenix, they need annual attention. The technicians will clean and adjust all the components and check the refrigerant level. A clean and adjusted air conditioner uses much less electricity and lasts longer.

If you’d like to learn more about an ERV or HRV and getting the most from your cooling system, call Forrest Anderson for all maintenance or repair needs.

Contact Forrest Anderson Today!

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