Story highlights
• Learn some science-backed techniques to staying cool
• Ideas include tips for house, car and more
We all do our best to survive the Valley’s scorching summer heat, counting down the days until we can once again experience the weather we’re here in Arizona to enjoy.
But sometimes our best is limited to what we have learned over the years about keeping cool — some of which is not even effective.
So what does work?
ASU News spoke to Arizona State University heat mitigation specialists Jennifer Vanos, Ariane Middel and David Sailor to learn what experts do to stay cool each summer.
Sometimes they rely on science-backed techniques you may never have considered. Other times, they employ simple, everyday habits to make Arizona summers more manageable.
Read on to learn more.
Note: Answers have been edited for length and clarity.
Question: What's the most effective way you have found to keep cool in general?
Vanos: The power of evaporation of water. In our dry climate, sometimes we can’t sweat enough to lose the heat we need to lose, so adding water to our skin creates “fake sweat,” you could say, and performs the same function without dehydrating us.
If you add a fan to support evaporation, it works even better. We just don’t want to use only fans in our dry climate when temperatures are above 104 degrees Fahrenheit — in this case, adding water to the skin or clothing (mist, dousing) is very important.
More on the science of sweat
Q: What are some things you do to keep your home cooler?
Middel: We barbecue more during the summer so we don't heat up the kitchen. We also rely on fans instead of lowering the thermostat because fans cool the person, not the room.
Sailor: I installed exterior window screens on two bedroom windows to reduce the amount of the sun's heat entering my house — this is more effective than interior blinds as it keeps the heat outside the home. I chose dark external screens because lighter color screens on the exterior can actually reflect more energy in through the screen mesh and into the window, which is much more transparent to the shortwave energy of the sun than the thermal energy of the warm exterior screens.
I recently had to repaint my house and recoat my flat roof. I chose more reflective colors to help reduce the amount of the sun's heat absorbed by my house and conducted into the building.
Q: Many Arizonans wonder about air conditioning. Is it more energy efficient to turn the AC off when leaving the house, or to leave it running at a higher temperature and let it cycle?
Middel: In general, it is usually more energy efficient to let the house get warmer when you are away rather than keeping it very cool all day. The bigger the temperature difference between indoors and outdoors, the harder the air conditioner has to work. So if no one is home, raising the thermostat reduces that heat gain and saves energy.
That said, I would not recommend turning the AC completely off during an Arizona summer. Homes can heat up very quickly, and extreme indoor temperatures can be dangerous for people, pets, plants and even some materials or electronics.
A better strategy is to set the thermostat higher when you are away, then cool the house back down before you return. A programmable or smart thermostat is useful for that.
So in essence: Don’t overcool an empty house, but don’t let it become dangerously hot either.
Sailor: All houses are somewhat leaky, so if the AC is running when no one is home, much of that cool air is slowly leaking out. For a typical home, about half of the indoor air is replaced by outdoor air each hour. So I find it wasteful to just keep the AC running if you are away for hours at a time.
I like to raise my set point while gone to about 85 degrees Fahrenheit so it doesn't take too long to get the house back to a comfortable temperature, and so the elevated indoor temperature does not adversely affect the surface materials in the house — high temperatures can warp wood flooring and musical instruments, deteriorate paint, make wallpaper peel and cause other issues.
Q: Keeping cool indoors is one thing. But surviving the intense summer heat outdoors is another. When you have to be outside, how do you stay cool?
Middel: In Arizona, carrying a sun umbrella can make a real difference, even though many people don’t do it because it feels weird. It creates portable shade, which directly reduces radiant heat from the sun. I sometimes wish parasols were more normalized here, especially for walking across parking lots, campuses or transit stops.
Also, people often assume less clothing is cooler, but in full sun that is not necessarily true. Lightweight, light-colored, sun-protective clothing can be better than shorts and a tank top if you are outdoors for a long time.
Sailor: First, I use a wide brim hat with a neck-protecting flap. If it is really hot, I use a chill towel around my neck. There are a number of good ones out there.
Vanos: I need to go outside in the middle of the day in the summer when I’m doing fieldwork to study extreme heat.
Some of my strategies include:
Hydrate well the day before and the day of.
- Douse with water on the head, hat and neck when needed.
- Work on acclimatization throughout the weeks and months beforehand, which means I do not avoid heat per se, but I safely expose myself to it over time while doing exercise to gain the physiological adaptations that make me able to handle high heat better when I need to.
Q: Do you have any tricks for cooling down your car quickly or making it more comfortable before getting in?
Vanos: One of my tricks for the kids is putting ice packs in the car seats when we are out and about, so they get to sit in a nice cool seat (instead of one that could burn them) when we get back to the car. I also like to use fans and spray bottles for the kids in the car.
Middel: I always use a windshield shade, and if I know the car will sit for a long time, I'll park in the shade whenever I can. A sunshade blocks solar radiation before it heats up the dashboard and steering wheel, which can make a big difference.
An exterior cover works even better because it keeps the sun from passing through the glass in the first place. But an interior sunshade is usually more practical for everyday use.
Sailor: I'm spoiled in that I can remotely turn my car AC on before getting in my car. Usually just a few minutes is enough to make a pretty good difference.
Q: What are some misconceptions about staying cool in the Arizona heat that you wish people would stop believing?
Vanos: I think I sometimes hear people say that they don’t sweat here! That is false. We sweat, and a lot, but because it’s so dry, it often evaporates from the skin before we notice. In a humid climate, we notice the sweat droplets condensing on our skin because the air above our skin already has a lot of moisture in it, so it’s unable to accept more water vapor as readily as in our dry climate.
So I worry that maybe people won’t hydrate enough because you don’t really perceive that you are sweating. They could be sweating even more than in a warm, humid climate, especially while exercising, so we always need to be keeping hydrated.
Middel: One common misconception is that longtime Arizonans can simply handle the heat better. You may know how to live with it, but your body is still under stress during extreme heat. Cooling strategies still matter: Drink water, seek shade, slow down, take breaks and get into air conditioning before you feel overheated.
Sailor: I'm not sure if it is a misconception, or just an aesthetic preference, but I have noticed that, even with our extreme temperatures, there are many homes that have dark roofs. A black roof absorbs more than 90% of the incoming solar radiation, compared with perhaps 10-15% for a white roof. That absorbed heat makes the roof surface very hot, resulting in more heat conduction into the house and more heat convection into the surrounding outdoor air.
Both of these cause increases in energy use for air conditioning, which, in turn, produces a positive feedback as AC units reject additional heat into the neighborhood.
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