Earlier this week, residents of Louisiana and Texas who were just pounded by Hurricane Laura endured a heat index of 109 degrees Fahrenheit (42.8 degrees Celsius). This weekend, California is expected to see its second record-breaking heat wave in three weeks. That’s just the U.S. this week; nearly every corner of the world is facing more dangerous heat waves as the climate crisis turns up the temperature.
To weather these oppressive temperatures, people are increasingly cranking up their air conditioners, a trend that is expected to continue as the world continues to warm. A recent analysis from Climate Central found that air conditioning use could rise 59% in the U.S. by 2050. Globally, demand is expected to triple over that time, according to the International Energy Agency (IEA).
As demand for air conditioning rises, the question of how to make the technology sustainable will become all the more important. One answer will be pursuing serious policy changes to promote efficient, climate-friendly cooling. But just as importantly, we have access to a number of low-tech strategies for cooling which can be implemented alongside plans to clean up air conditioning, solutions that are available right now.
The reality is that air conditioning is most needed in places where many don’t yet have access because of cost and even lack of access to electricity to run it in the first place. As of 2018, just 10% of India’s population had air conditioning. In the world’s hottest regions in Africa, Asia, Latin America, and the Middle East—home to 2.8 billion people—only about 8 percent of the population owned an air conditioning unit. All told, a 2019 study found that between 1.8 and 4.1 billion people living in the developing countries who regularly experience temperatures that can spur heat-related stress lack access to cooling technology.
“In the developing world, air conditioning is a luxury item,” said Narasimha Rao, an assistant professor of energy systems at Yale University at co-author of the 2019 study.
Access to air conditioning is set to increase with rising wages. In India, for example, the IEA predicts that 45% of the population will own an air conditioner by 2050. But that will still leave the majority of the population vulnerable to extreme heat, which is expected to get dramatically worse by then.
It’s clear that the world needs a plan to help global populations beat the heat. Scorching temperatures aren’t just uncomfortable, they can spur heat stroke and increase instances of stroke and other health crises. In the U.S., extreme heat is the single biggest weather-related killer.
But the cruel irony is, without major changes, upping the world’s use of air conditioners will dramatically increase global warming. That’s due in large part to the refrigerant chemicals that power air conditioners. Most cooling technology emits greenhouse gases called hydrofluorocarbons (HFCs), which warm the climate thousands of times more than carbon dioxide.
More climate-friendly alternatives to HFCs—like hydrofluoroolefins (HFOs), ammonia, and propane—exist. But those alternatives come with issues, too. HFOs are less harmful to the climate than HFCs, but when they break down in the atmosphere, they create a compound called trifluoroacetic acid that could potentially damage the environment. Ammonia and propane can both be harmful when they leak, and are prone to catching fire, which is obviously not a good thing.
“You don’t really want the refrigerant running through your air conditioner to be the same as the fuel running through your barbecue grill,” said Stan Cox, the author of Losing Our Cool: Uncomfortable Truths About Our Air Conditioned World and fellow at the Land Institute.
There’s also the problem of where electricity comes from. Even air conditioners powered by these relatively clean alternatives would run on the world’s largely fossil fuel-powered grid. According to a recent United Nations report, air conditioning and refrigeration accounted for 17 percent of global energy demand in 2018.
More air conditioning that relies on our current electricity mix would be a disaster for the climate. The best solution to this would be to rapidly transition away from dirty energy altogether. But the more energy demand increases, the more difficult it will be to keep up.
An important way to decrease electricity demand from air conditioning is to make the technology more energy-efficient. A 2018 International Energy Agency report notes that the average air conditioner sold today uses over twice as much energy as the most efficient models. The least efficient technology, which is often found in low-income households, uses even more energy, making it more climate-warming and expensive. But while switching over to more efficient technology is definitely a good idea, it could be difficult to keep pace with rising demand.
“Improvements in efficiency generally cannot keep up with growth in consumption,” said Cox. “For example, between the mid-1990s and mid-2000s, energy efficiency of U.S. residential air conditioning equipment in use improved by 28%, [which is] pretty good. But during that same period, total electricity consumption by residential air conditioning increased by 37%…because more households were using air conditioning, houses were getting bigger, summers were getting hotter.”
There’s another complimentary way to decrease energy demand for air conditioning: We could use less of it.
That’s not to say people should be forced to bear extreme heat, or that we shouldn’t expand air conditioning infrastructure to those who need it. As global temperatures continue to climb, air conditioners provide important and sometimes life-saving relief from the heat. But there are plenty of low-tech ways to keep buildings cool without driving up greenhouse gas emissions, too.
For one, buildings can be constructed with cooling in mind. Homes with poor insulation, for instance, tend to let far more heat in and make residents reliant on expensive, constant air conditioner use, racking up high energy bills and increasing carbon and HFC pollution. In the U.S., the most poorly insulated homes tend to be low-income ones.
Rather than merely providing those living in these areas with high-powered air conditioning, we could completely overhaul inefficient buildings. Retrofitting and weatherizing homes may not be as sexy as fancy new air conditioners, but doing so would better regulate temperatures. That could go a long way to decrease the need for air conditioning while lowering energy bills, too. A comprehensive program like the one laid out in the Green New Deal for public housing alone could also create hundreds of thousands of jobs.
This isn’t just a solution for the U.S., though. The 2019 paper Rao co-authored shows that in some parts of the Global South, up to 20% of the population lives in slums, which tend to have homes that are poorly insulated and energy inefficient. Rao highlighted the problem with metal roofs, for instance, which are “the worst thing to have in terms of ventilation.”
Unlike metal, some construction materials, such as brick, slate, concrete, and stone, have a high thermal mass. That means they can absorb and release heat more slowly, rather than quickly warming when the sun beats down. It’s this principle that keeps big stone churches cool in the summer heat. Providing global populations with adequate housing using these or other building materials that lock in cool air is a necessary step in closing what the paper calls the “cooling gap.”
Structures can also be designed to maximize the cooling potential of gusts of wind. Wind towers, for instance, can be constructed like chimneys atop homes to draw in the cooler breezes that swoosh around above buildings. This can be made even more effective by placing cooling ponds of water beneath these towers. These design elements may sound futuristic, but they have been used for thousands of years, notably in ancient Persia.
Strategically planting trees to provide shade can also play a role. One 2019 study suggested that tree cover can lower a neighborhood’s summer daytime temperatures by as much as 10 degrees Fahrenheit (5.5 degrees Celsius). The same principle can be applied to roofs by installing rooftop gardens, which can help regulate a building’s temperature variability, insulating it from cold or hot air outside. A vast array of research shows that green space also has enormous benefits for mental health, a strong co-benefit to the cooling properties of more tree cover.
These plant-based methods could be especially effective in locations where concrete and other paved surfaces lock in high temperatures as part of the urban heat island effect. These areas are disproportionately occupied by low-income people of color dealing with inefficient housing, underscoring that there are multiple avenues to help people most in need of cooling.
Roofs can also be painted light colors to reflect the sun’s rays, which can help decrease temperatures inside a home. Advances are ongoing, with a study published this summer highlighting a new blend of paint that can reflect 98% incoming sunlight. Scientists have even developed photochromic glazes for roofs, which become more transparent when there’s less sun and more opaque when there’s more, like transition-lens sunglasses.
Similar glazes for windows have been developed, too. Spectrally selective window coverings block out the sun’s infrared rays, while still letting the daylight in.
Though these low-tech (and, in the case of photochromic roofs and windows, high-tech) cooling methods may sound like they belong in the realm of aspirational tiny house YouTube channels. But some of them are actually used in public housing in Singapore and Vienna. These strategies won’t eliminate the need for air conditioning altogether, and we should still push for more equitable access to it. But for the climate’s sake, as we expand access, there are ways to make the world less reliant on the technology.