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With one heat wave after another rolling across the country this summer, you may be spending more time indoors. But if you’re simply lowering the thermostat when it’s extra hot outside, experts say you’re using your AC all wrong. Chances are, you’re making more mistakes than you realize when it comes to keeping your home cool.
“Comfort is about more than your thermostat setting,” says indoor air quality expert Stephanie Taylor, M.D., M.Arch., medical adviser for ThinkLite Air. “The radiant heat coming in through windows, the movement of air, and indoor air quality also have an impact on what people perceive as comfortable.”
However, the biggest issue with comfort is humidity. Think about how sticky it feels outdoors when humidity levels soar. It’s no different inside your home. “If you pay attention to the humidity level indoors and manage your indoor environment according to that, you’ll be more comfortable,” says Taylor.
Read on to learn how to use your air conditioner properly to keep your space livable, even on the hottest days.
How Air Conditioning Works
It’s helpful to know the basics of this technology so you can use it as efficiently as possible. In a nutshell, air conditioning absorbs heat and humidity from your indoor air and transfers it outside.
“Inside the space, your system is rotating air across a cooling coil, which changes the moisture content in the space,” says Robert Bean, retired engineering technologist and American Society of Heating, Refrigerating, and Air-Conditioning Engineers fellow. “Moisture is collected and removed, making dehumidification a byproduct of the cooling process.”
Ideally, the AC unit should be properly sized for your home, because bigger isn’t necessarily better. A unit that’s too large will keep shutting off. “We don’t want the air conditioning to cycle on and off. You want it to run for a longer period of time to remove the moisture from the air,” says Bean.
However, you shouldn’t think that turning the thermostat to a lower temperature is going to speed up the cooling process. “It cools at one rate, regardless of where you set the thermostat,” says Taylor.
With that in mind, where should you set your thermostat? There’s no one-size-fits-all recommendation because there are too many variables, such as your home’s age, weather conditions, and personal preference. But you can use an inexpensive hygrometer to monitor your indoor humidity level, rather than relying on the thermostat alone. The aim is to keep humidity between 40 and 60 percent (the ideal range for both health and comfort) by tweaking your thermostat accordingly, says Taylor.
Should You Turn Your AC Off if You’re Not Home?
Shutting off your AC if you’re leaving the house or going on vacation is a bad idea. That’s because everything in your house, from the building materials to the furnishings, retains heat.
“Your home stores heat like a thermal battery,” says Taylor. “The air temperature drops first, but the walls, floors, furniture, and carpet keep releasing heat. That is why comfort can lag behind the thermostat.”
You also shouldn’t turn your AC way, way up when you’re away for the day. Setting the thermostat to a higher temperature when you’re at work sounds like it will save money, but that’s simply not true.
“If you choose a high setback temperature, such as 80 degrees Fahrenheit, the house needs a huge head start when it is time to start cooling,” says Wes Davis, director of technical services at Air Conditioning Contractors of America.
Additionally, if you start cooling in the afternoon, the unit has to cool your house during the hottest part of the day. “This is a recipe for discomfort and very little energy savings because the unit must run long into the night to cool your home,” says Davis. Essentially, it’s playing catch-up.
How to Help Your AC Do Its Job Better
There’s not just one single change you can make to improve your home’s comfort level, but these expert tips can help you feel more comfortable, even during a heat wave.
Get a Tune-Up
Just like you take your car in regularly for an oil change or tire rotation, your AC system needs periodic maintenance because coils can get dirty or refrigerant loses its charge.
“Some customers are skeptical about maintenance, but it’s less expensive to invest in upkeep than waiting for something to break,” says Matthew Lefler, vice president of franchise operations for Service Experts. “We want to help you keep your system running well so it lasts and you stay comfortable.”
Change Filters Regularly
Check filters monthly during peak season. A clogged filter makes it harder for air to move through your unit, so change them regularly, says Lefler. Set a reminder on your phone if that makes it easier.
Cover Windows
Lower blinds and draw drapes, such as blackout drapes, to keep heat out in the first place. Do this in the morning before the sun begins to stream indoors, says Bean. One study showed thermal comfort and energy savings improved most with the use of honeycomb cellular shades. You also can look for window coverings with AERC ratings that show energy efficiency levels.
Limit Cooking
If there’s a heat wave, plan ahead and treat yourself to takeout, throw something on the grill, use a slow cooker, or make sandwiches. Anything that adds heat and/or moisture to your home isn’t a good idea, says Bean.
Don’t Do Laundry at Midday
Save that task for the cooler parts of the day. Also, make sure to run your bathroom vents to get rid of moisture from showers and baths, says Taylor.
Run Fans When You’re in the Room
Turn them on only when you’re in the room because they don’t cool the air itself. Instead, the air movement increases evaporative cooling by removing moisture from your skin, says Taylor.
Open Windows at Night in Cool Climates
If you live in a cool climate, you can open the windows to allow fresh air to circulate in the evening, says Bean. Side note: Of course, this isn’t always possible if you have seasonal allergies, air quality concerns, or security concerns.
Invest in Exterior Shading
Keeping heat off your home helps tremendously. Consider long-term solutions such as installing outdoor awnings on west- and south-facing windows to reduce radiant heat gains, says Davis.
Plant Trees
This isn’t a short-term solution, but shade helps keep the building cooler overall, says Taylor. Studies have shown that trees that directly shade buildings decrease demand for air conditioning by shading surfaces to reduce the heat transmitted to buildings. Of course, trees also improve air quality, manage stormwater runoff, provide habitat for wildlife, and beautify your yard, so it’s a win all around when you plant trees.
