Illustrations by Guyco

Before modern cooling machines enveloped civilization in frigid air, humans living in hot climes used all sorts of techniques to stay reasonably comfy. Egyptians fashioned homes with mud and stone. Domed mosques and temples in the Middle East and India funneled hot air upward. Dwelling in subterranean chambers kept denizens of Cappadocia in Turkey and Petra in Jordan from breaking a sweat. Some cultures draped water-soaked fabric over open windows; others topped their roofs with thatch or earth to diffuse heat. Roman emperors had their plebeians haul snow from distant mountaintops and pile it along palace walls. More recently, residents of America's Deep South kept their homes airy with vaulted ceilings, spacious front rooms, wraparound porches, and picture windows.

Then, in the early twentieth century, a tenacious young engineer named Willis Carrier introduced us to the miracle of indoor climate control. Today, the company that Carrier founded earns $11.4 billion in annual sales, but its products, having revolutionized the way Americans live, remain the least efficient appliances in a typical household. They devour 16 percent of an average household's annual energy tab, producing the equivalent of 2,290 pounds of carbon dioxide emissions. "We've always taken air-conditioning for granted," Gordon Holness, president of the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE), told me recently. "We've got into these lazy patterns because energy has been readily available and cheap. Now we're realizing there isn't an endless supply."

The dilemma isn't all that much different from that faced by the automobile. On its evolutionary time line, the air conditioner today is about where the automobile was in the 1970s. It is a pathetically inefficient machine to which we have become both psychologically addicted and economically dependent, blind to its environmental footprint. Since Carrier introduced his "chillers" more than a century ago, the basic mechanics of how we cool air haven't changed. It's fair to say that the most state-of-the-art air conditioner today is akin to a gas-guzzling muscle car from 40 years ago. To carry the analogy forward, the automotive industry finally responded, albeit at a snail's pace, with improved fuel economy, smaller cars, and, more recently, hybrids, hydrogen cells, plug-in electrics, and various types of alternatively powered vehicles. Unfortunately, air conditioners don't have an equivalent of the Prius, at least not yet.

Carrier was born in 1876 near Angola, New York. Those who knew him say that as a child he had "tremendous power of concentration." He excelled academically, winning a state scholarship to Cornell University.

Soon after graduating, Carrier was hired by the Buffalo Forge Company, which manufactured components for ventilation systems. His bosses, William and Henry Wendt, recognized his exceptional analytical skills and assigned him to R&D. In 1902, while waiting for a train in Pittsburgh, Carrier had his "aha" moment. It was a foggy evening, which got him thinking about the interaction between condensation and cooling. This led to an interest in what he termed "dew-point control," the ability to infuse air with very precise amounts of moisture, thus affecting its humidity and temperature.

That same year, the Sackett-Wilhelms Lithographing Company in Brooklyn, New York, enlisted Carrier to solve an ongoing problem with its multicolor printing press. Fluctuating humidity inside the plant caused the paper to stretch, shrink, and curl between passes, and because the overlaid colors wouldn't align properly, text and images were blurred. Carrier invented a network of fans and coils that circulated cold water to lower the air temperature in the press and had some success in maintaining the relative humidity at exactly 55 percent no matter what the weather was like outside.

Carrier still wasn't satisfied. He continued experimenting with humidity control, eventually developing an entirely self-contained unit that used misters to saturate the outside air with water, which cooled it. Next, to remove excess water, a fan pushed the saturated air through a set of vertically aligned metal plates called baffles. Water vapor clung to the plates and then drained into a collection tank. Finally, a heater warmed the chilled, dry air until it reached the desired temperature and humidity.

Carrier's clout as a big thinker was enough to persuade the Wendt brothers to launch, in 1907, a new subsidiary to focus exclusively on heating, ventilation, and humidification. They named it the Carrier Air Conditioning Company of America and installed the 31-year-old only child from rural New York as vice president.

The machines that Carrier invented became a national obsession. He sold humidity control systems to dozens of customers in the film, tobacco, pharmaceutical, textile, and other industries. For the first time, they didn't have to worry about humidity destroying their goods during production.

In 1922 Carrier patented his "centrifugal chiller." Unlike his humidity systems, which targeted industrial applications, the chillers were marketed mainly for personal comfort. Two years later, he installed a unit in the basement of Detroit's J. L. Hudson Company department store. Hudson's ran daily newspaper ads during the summer months proclaiming that "Pure Fresh Cool Air Makes Shopping in the Basement a Pleasure" and "On Warm Days It's 8 to 12 Degrees Cooler in the Basement Store than Street Temperature." Shoppers went gaga, and department stores across the country clambered to purchase their own Carrier chillers.