Beat the heat with these innovative AC alternatives

This summer, many parts of the United States have been sweltering under heat advisories for days or even weeks at a time. During the third week of June, residents of 17 states were sweltering under a heat dome.

In addition to seeking out shade and staying hydrated, millions of people across the country have inevitably been relying on their air conditioners, and understandably so. And while air conditioning can be an essential recourse at times of extreme heat, its widespread use throughout summer comes at a cost.

During the hottest parts of the day, they strain energy grids, “which means that what we do in buildings makes it harder for the grid to do its job of providing affordable, reliable electricity,” explains Amanda Smith, senior scientist with Project Drawdown.

They also contain refrigerants, which are greenhouse gases thousands of times more effective at trapping heat in the atmosphere than carbon dioxide.

If you can’t afford air conditioning or would prefer not to use it, what are the alternatives?

From simple to more complex, here is a selection.

Shades, fans, and barbecues—fast fixes

Instead of cooling the hot air in your house, try to prevent heat from accumulating in the first place. That’s easier said than done in extreme heat, but as a first step, close your windows and pull the drapes or lower your blinds, especially on south-facing windows, in the daytime. Open them back up at night to allow warm inside air to escape and cooler nighttime air to enter.

Fans won’t actually cool your space, but by moving air around, they can help evaporate sweat from your body, which cools you down. (Ceiling fans are particularly effective.) And if you have your own property and enough space planting trees is an excellent, long-term solution.

Something else you can do to cool the house? Cook outside. “Cooking is a huge source of heat,” says Eric Peterson, a civil engineer at the University of Leeds. So, if you’re cooking something that requires heat, “Get a little portable barbecue and put it out on the veranda and do as much as possible of your summer cooking outside.”

New cooling tech enters the home

You’ve closed the drapes and you’re sitting in the shade. What if it’s still too hot?

If you’re in a dry climate, you could try an evaporative cooler. Also known as swamp coolers, these devices are commonly available as window or portable units and pass air over water-saturated pads. The water then evaporates, cooling the air, which is then circulated around the room. Because the cooling air contains water droplets, they are not suitable for humid environments.

These cooling systems are cheaper than traditional air conditioners, and they use only a fourth of the energy to run, according to the Department of Energy.

In some places, such as India, evaporative cooling is also deployed in a low-tech way using clay pots and has been an effective cooling strategy for thousands of years.

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Another increasingly popular option—so popular that they’ve been outselling gas furnaces in the U.S.— is to install heat pumps, which can both warm the house in winter and cool it in summer. More than 30 countries around the world are subsidizing the purchase of heat pumps because the technology can cut a home’s energy use in half, making heat pumps a sustainable alternative to AC.

Most heat pumps work by taking heat from the air outside to warm the home or sending warm air outside to cool it.

Instead of using air to cool (or heat) your house, some heat pumps go one step further and use water, which is more effective at transferring heat than air.

Geothermal heat pumps, another take on these water based heat pumps, combine the efficiency of water with the naturally-cooling properties of the ground. Summer surface air temperatures are warmer than those below ground, and these systems bury water-filled pipes to naturally keep them cool.  

Designing better roofs

Heat can escape through roofs, particularly with inadequate attic insulation, and dark rooftops are similarly responsible for absorbing large amounts of solar radiation and warming the house.  

Green roofs  are roofs with vegetation planted on them. They are popular in parts of Europe, especially Austria, Germany, and Switzerland, and in the Swiss town of Basel they are required by law. They provide shade from direct sunlight and cool the air directly through evapotranspiration (absorbing water through their roots and expelling it through their leaves—essentially the same physics as are used by swamp coolers.)

The downside of green roofs is their weight—they often need fortified roofs and require maintenance and upkeep.

A simpler alternative to a green roof is a cool roof. And the simplest way to a cool roof, says Peterson, is to “paint it white.” White not only reflects solar radiation off your house, he says, “it emits 90 percent of the thermal energy out into space.”

Some companies are developing what they claim are highly efficient cool roof coatings; but in the meantime, says Peterson, homeowners can just “do what they do in Greece and slap some whitewash on every summer.”

Radically rethinking how we build

The very design of many of our buildings is not conducive to cooling them efficiently—which, says Salmaan Craig, an associate professor in architecture and urban design  at UCLA, is a direct result of air conditioning’s existence. “We don’t get high rise glass towers 50 or 100 years ago, because they’re not possible without air conditioning,” he points out.

In some respects, the way forward is to look back at how some cultures in traditionally hot environments have adapted their buildings to be as cool as possible. For example, windcatchers, also known as wind towers or wind scoops, were developed in Persia thousands of years ago, and harness cool breezes that they send into a building while pushing out warm air.

Also characteristic of many buildings in warm climes: building materials that have what is known as higher thermal mass. That includes bricks, stone, concrete, and adobe, all of which effectively absorb heat without radiating it inward into the building.

 Craig notes that buildings in traditionally hot environments are constructed “with what you might call an internal thermal hierarchy: rooms are more inward looking, often into a central courtyard – which may be shaded and have cooling water features, and then you have an outer perimeter of rooms to protect the interior of the house from the heat outside.”

The key, adds Smith, is to ensure that air conditioning doesn't have to be a first resort.

“I want us to think of mechanical air conditioning more as a need for people in extremely hot climates,” she says. “It’s like a cherry on top in terms of comfort.”