When to open windows vs. use AC in late summer, early fall

When to open windows vs. use AC in late summer, early fall

Late summer has an reinvigorating energy to it that no other part of a season can claim. Travel and vacations wind down, kids are headed back to school and all those school-related activities start to pick back up.

At night and early in the mornings, there may be a chill in the air that signals autumn’s arrival is approaching fast. Homeowners could be tempted to take that signal as a reason to turn off their air conditioners, open up their windows and let fresh air fill their homes.

There are some undeniable benefits to cracking a few windows in the home when possible, which we’ll cover in this post. You could potentially save a few dollars on the month’s utility bills if you are smart about when you decide to open your home’s windows.

After all, less AC use means lower utility bills, right? It’s possible, but there’s a strategy to when you should rely on the AC and when it’s OK to open up some windows in the house. Let’s get started on breaking down that strategy to help you stay comfortable and maybe save some money on energy costs.

Can I open windows at night and use the AC during the day?

It’s a common strategy in late summer to open windows in the home at night when the air outside has cooled down. During the day, the AC can kick back on and keep the house cool.

Though this strategy looks like it makes sense at first glance, it may not always work. First, you could be wasting energy. Once you open your house’s windows, that air that’s been inside will escape and the air that’s outside will enter.

In some cases, you could be letting in air that is warmer, even if just slightly. When you turn your AC unit back on, it will have to work that much harder - and cost you that much more - to get the indoor air temperature back to where you want it.

You could also be letting in humid air. Even if it’s closer or cooler than the indoor temp, air with moisture locked in it will be more uncomfortable for people indoors. That moist air will also be absorbed by furnishings and carpet. Everything is going to feel just a little bit off at best - or downright sticky at worst.

Extra moisture in the air could make AC work harder

By opening your windows when the air is still humid, even if it’s cooler, you are letting in all that extra moisture. Results from a study conducted in Florida still ring true today. In that study, researchers focused on a central Florida that had typical furnishings and a lot of carpet. During the day, the home was air conditioned. At night, the windows were opened up at night. This allowed moist air into the home.

Now, when moist, humid air comes into a home, the air conditioning unit has to work that much harder. That’s because moist air carries more heat than dry air. Many who live in the Midwest can relate to this. It’s not the heat; it’s the humidity, right?

But that moisture in the air, while also making everyone inside more uncomfortable, makes the air conditioning work harder, too, the study found. At night, according to the study, nighttime ventilation increased the amount of moisture that had to be removed by about 5 gallons per day more than a house that had its windows kept closed at night.

There was not as much energy saved either as you might expect. The study found that elecricity use did in fact drop by about 30% when the AC was not used at night. However, the added work needed to remove the moisture in the air increased power usage during the day when the AC was on by about 21%.

Open windows once the weather cools

This does not mean opening the windows later in the summer and in early fall is not an option.

If you live in a cooler, northern climate, where late summer outdoor temperatures average around 70 degrees or less in the evenings, then you could see the benefits of turning off the AC and opening windows, as long as humidity levels are low.

If you are able to take advantage of letting in cooler air from outside and shutting down the air conditioning for the night, then there’s even more you can do to trap the cool air. Once you wake up in the morning, close all the windows plus window blinds to keep all that cooler air inside.

Don’t wait too long, though. With open windows, the air in your home will heat up as the outdoor temperature rises. That’s why it’s a good idea to close the windows when it’s still cooler out.

Keeping windows open more often is better for you

No, seriously. When you get the chance, crack open a few windows in your home. It could improve your health.

It’s that fresh air that makes the difference, according to a National Post article. Keeping your windows closed up for too long can lead to a buildup of toxins that are already in your home. That includes mold spores, dust, smoke, viruses and bacteria. If you keep breathing in the same air cycling through your home, you stand at a higher risk of becoming sick.

Breathing in all that not-so-clean air can lead to feeling tired and drowsy. In more severe cases, it could also cause headaches, dizziness, nausea and irritation in your eyes, nose and throat.

Keep your AC running at its best

No matter your comfort preferences this time of year, your air conditioning unit depends on smart energy use habits and regular servicing to stay operating as efficiently and reliably as possible.

Comfortec can help you keep your home’s entire air conditioning system running at its best. Take the first step in protecting your AC by setting up a service call today. We are also available 24 hours a day for emergency service.

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