No AC? No sweat. How to make a DIY air conditioner and 3 other heat wave hacks

HomeServe reports on DIY hacks for cooling your home during heat waves, including making a simple air conditioner, using shade, adjusting ceiling fans, and managing humidity. (HomeServe/HomeServe)

By Matt Schmitz for HomeServe

No AC? No sweat. How to make a DIY air conditioner and 3 other heat wave hacks​

If your air conditioning goes out just as a heat wave or heat dome hits, the threat level while you're sweating it out — until the emergency HVAC tech arrives or the weather breaks, whichever comes first — can range from discomfort to danger. In a heat emergency, people without access to properly functioning AC need to find alternative measures to stay safe. Whether you're just trying to keep cool enough to sleep through the night or lowering the temperature is a matter of life and death, HomeServe has DIY home hacks that can offer immediate relief amid the summer swelter.

​According to a report from The Weather Channel citing data from the Centers for Disease Control and Prevention as well as the National Oceanic and Atmospheric Administration, some 273 people died from heat-related causes from 2015 to 2024 — making heat the deadliest weather event by far. Older people can be more susceptible to the dangers of heat-related illness, as their bodies often have greater difficulty acclimating to temperature changes due to medical conditions, medications and just the general bodily challenges associated with aging. That's particularly true for low-income, inner-city elderly adults who, according to a 2024 study published in The Central European Journal of Medicine, tend to be more vulnerable to the "urban heat island" effect due to the high concentration of buildings, paved surfaces and insufficient green space, oftentimes compounded by poor insulation and limited air conditioning availability.

​“Social factors such as isolation and lack of access to healthcare services also play a significant role in urban settings, where older adults may live alone in apartments with poor ventilation,” the study’s authors stated.

​If you find yourself without AC during extremely hot weather, try one or more of these heat-mitigating measures:

Build Your Own Air Conditioner

Things You’ll Need

You can make a makeshift “air conditioner” using common household items. All you need is:

  • A disposable cooler
  • A desktop fan
  • An oatmeal container or similarly cylindrical receptacle
  • A small handsaw or knife
  • A marker
  • Ice

Step-by-Step Instructions

  1. On top of the cooler lid, trace a hole around the circumference of the fan.
  2. ​Use your cutting instrument to carve a hole in the lid slightly smaller than the circle you drew.
  3. Cut off the closed end of the oatmeal container so that it's open on both sides.
  4. Trace the opening of the oatmeal container onto the side of your cooler.
  5. Cut out the hole.
  6. Insert the cylinder.
  7. If your hole is too big, don't fret — use duct tape to seal the gap.
  8. Fill the cooler with ice.
  9. Secure the fan over the hole in the lid and turn it on so that it's blowing downward into the cooler.

The focused blast of ice-chilled air from this Rube Goldberg-ian contraption will help cool down your body temperature.

Reflect the Rays to Beat the Heat

We tend to think in binary terms when it comes to extreme temperatures: It's either "cold" or it's "hot" out. But there are important distinctions to be made — and comfort-increasing opportunities to be exploited — by thinking in terms of air temperature versus radiant temperature and vice versa. On a sunny day, simply stepping out of the direct sunlight and into the shade can reduce the temperature by 10 to 15 degrees. So if you have window treatments to help block the surface-heating rays of the sun — or if you're really fortunate to have blackout curtains or shades — pull them shut. But not everyone's home is sufficiently outfitted against the solar sizzle and may be unable to incur the expense of window treatments.

Try the following heatwave-foiling hack, recommended by the Federal Emergency Management Agency, to deflect danger, again using common household items.

Things You’ll Need

  • Aluminum foil
  • Cardboard
  • Scissors
  • Tape

Step-by-Step Instructions

  1. Cut the cardboard into manageable pieces based on the size of your windows.
  2. Cover your cardboard pieces with aluminum foil, with the shiny side of the foil facing out and the dull side against the cardboard.
  3. Place the foil-covered cardboard in your windows, covering as much of the glass surface as possible.
  4. Use tape to secure the pieces in place, if necessary. The foil will reflect the sun's rays outward and away from your home, mitigating the radiant heat effect and cooling your living space by several degrees.

Make Sure Your Ceiling Fan Is Set for Summer

Painfully obvious advice: If your home's AC is out and you have fans, run fans. That goes for your ceiling fan, too, if you have one — but the advice isn't as simple. You may assume using your ceiling fan is as easy as flipping the switch, but changing the direction in which your fan's blades spin depending on the season helps keep your home more comfortable during an AC outage.

The direction you should have your fan blades rotating in is the opposite in the warmer spring and summer months as it is in the colder fall and winter months. Most modern fans have directional controls on either a remote control or wall panel that enable you to adjust which way the blades turn and, therefore, how air is distributed throughout the room.​

So all you have to do is adjust the switch to set your ceiling fan to spin counterclockwise during the summer months. That enables the fan to push cool air down to the floor, evaporating perspiration and creating a wind-chill effect, which makes you feel cooler without actually changing the room’s temperature.

When your blades are set for summer, you should feel air movement while standing under the fan. If you don’t, your fan is spinning in the wrong direction.

For context on why fan direction matters, during the fall and winter, blades should spin in the reverse position, clockwise, and run at low speeds. That pulls cool air upward as the gentle updraft pushes warm air, which naturally rises to the ceiling, down along the walls, and back to the floor, making the room feel warmer.

Adjust Your Whole-House Humidifier

Cliches sometimes become expressions of folksy wisdom because they’re true. To that end: It’s not the heat. It’s the humidity.

If your AC is functioning fine but isn’t sufficiently staving off seasonal saturation of the air, it might be due to the setting of your whole-house humidifier. As opposed to the cold, dry winter, the last thing you need in the warmer, wetter weather is more moisture in the air. So if your house is starting to feel like the wet sauna at your favorite spa, it’s time to set your home’s humidifier for summer.

Step-by-Step Instructions​

  1. Find your whole-house humidifier. If you have one, it'll typically be near your furnace, attached to the ductwork.
  2. Locate the control switch, or humidistat, typically found above the humidifier, and either turn it off or adjust it to the lowest setting.
  3. If your humidifier has a bypass duct damper, adjust it to the "summer" setting to close it — turning it counterclockwise to be perpendicular to the duct — further preventing moisture infiltration.
  4. Turn off the water supply to the humidifier by following the quarter-inch copper or plastic line to the valve and shutting it, again by turning it clockwise to be perpendicular to the pipe.

This story was produced by HomeServe Editorial and reviewed and distributed by Stacker.