Schemes for staying cool have often been extravagant, inefficient and expensive, but the advent of the air conditioner in the early 20th century made beating the heat feasible. In 1979 Time magazine writer Frank Trippett commented, “It is…no exaggeration to say that Americans have taken to mechanical cooling avidly and greedily. Many have become all but addicted.” That still rings true—and Americans aren’t the only ones chilling out anymore.
Back in the third century, Roman emperor Elagabalus dispatched 1,000 slaves to the Alps to gather snow, transport it to the capital by mule train and pile it next to the imperial villa. In a similarly impractical scheme, those tending U.S. president James Garfield, mortally wounded by an assassin’s bullet in July 1881, kept their patient comfortable by blowing air through cotton sheets doused in ice water. The arrangement lowered the room temperature by 20 degrees but consumed half a million pounds of ice in two months. In modern times avoiding soaring temperatures is a less strenuous activity. Air-conditioning was a hit as soon as it was switched on at J.L. Hudson’s Department Store in Detroit in 1924 and the Rivoli Theater in New York’s Times Square on Memorial Day weekend in 1925. It was standard in offices by the 1950s, after studies showed that workers were more productive in cooled environments. Today more than 85 percent of American homes contain one or more air-conditioning units. Compared to Elagabalus’s profligate version, modern air-conditioning is an affordable luxury that nevertheless comes at an environmental cost: Cooling an average American home emits about two tons of carbon dioxide each year.
When a Roman emperor wanted to cool off two millennia ago, he merely commissioned a huge reflecting pool to chill the hot breezes, as Hadrian did at his villa in Tivoli, outside Rome. In the 16th century Cardinal Ippolito d’Este, son of Lucrezia Borgia, beat the summer heat with even more elaborate water features at the nearby Villa d’Este, where among the cascades, pools and fountains, a statue of the goddess Artemis of Ephesus still squirts water from each of her 20-odd breasts. Ding Huan, a Chinese engineer, had a grandiose but slightly more straightforward vision for bringing relief to ruling members of the Han dynasty: a giant rotary fan requiring a small army to operate. Of course, most folks over the centuries have had to employ simpler means of staying cool. Ancient Egyptians achieved a kind of refrigeration by fanning clay jars filled with water, causing the temperature to drop as the contents slowly evaporated. Medieval Persians built wind towers above their houses to capture prevailing breezes and circulate them through the rooms below, which kept out desert heat with thick walls and small windows. Modern air-conditioning combines both concepts, removing humidity from the environment and circulating chilled air.
The simple hand fan was in use in China 3,000 years ago, but the Han dynasty took the concept to a new extreme a millennium later with a fan machine consisting of seven 10-foot-wide rotaries that were turned manually. Chinese-style temperature control became even more elaborate in the eighth century, during the Tang dynasty, when Emperor Xuanzong chilled in a “cool hall” equipped with huge fans that moved air over a series of fountains. Despite these early innovations, the home air conditioner was virtually unknown in China as late as the 1990s. Change came quickly: Today as many as 50 million units are sold a year in China, and sales are estimated to be growing by 20 percent a year there and in India. The developing world is falling under the technology’s spell—as the U.S. did in the 1950s, when a Carrier air-conditioning advertisement promised, “There’s something masterful about flipping switches and turning knobs, and then seeing and feeling how your air-conditioning responds.” The newest challenge is to master ways to stay cool without warming the planet. Refrigerant gases currently in use could represent 27 percent of the contribution to global climate change by 2050.
In the early 19th century, Boston businessman Frederic Tudor made a fortune harvesting ice from New England lakes and shipping it around the U.S., especially the South, and to points as distant as Japan, India and Australia. Henry David Thoreau, watching Tudor’s ice cutters at work on Walden Pond, described the commercial venture poetically: “The sweltering inhabitants of Charleston and New Orleans, of Madras and Bombay and Calcutta, drink at my well.… The pure Walden water is mingled with the sacred water of the Ganges.”
Tudor made ice a household staple and proved there was money in offering relief to the sweltering. The cooling industry took a leap forward in 1914, when the Charles Gates mansion in Minneapolis became the first mechanically air-conditioned home. However, the apparatus—seven feet high, six feet wide and 20 feet long—did not lend itself to widespread use. Nor did the first window units, introduced in 1931, which cost between $10,000 and $50,000 ($120,000 to $600,000 today). By 1953, though, annual sales of affordable window units hit one million in the United States, and by the 1980s the U.S. was using more air-conditioning than all other countries in the world combined.
In De Architectura, probably written in the first century B.C., Roman architect and engineer Vitruvius claims that maintaining comfortable temperatures is all about situating rooms properly—for instance, “summer dining rooms to the north, because that quarter is not, like the others, burning with heat during the solstice.” The wealthy augmented such passive techniques by channeling water from aqueducts into pipes running through their walls. Many Roman homes had a central atrium with a shallow pool of water, the evaporation of which tempered the air that flowed into the surrounding rooms.
Benjamin Franklin and chemist John Hadley also experimented with evaporation as a cooling method. Using bellows to blow air over the bulb of a thermometer to which they continually applied ether with a feather, they caused ice to form and lowered the thermometer’s temperature to seven degrees Fahrenheit while the rest of the room remained at 65 degrees. Franklin attributed the drop in degrees to the effect of the evaporating ether. Since evaporation is a principle behind modern air-conditioning, Franklin’s comment on this discovery was prescient, if a slight exaggeration: “From this experiment, one may see the possibility of freezing a man to death on a warm summer’s day.”
Benjamin Franklin, it is claimed, stumbled upon the idea that evaporation correlates with temperature reduction when he perceived that he stayed cool while wearing a wet shirt that slowly dried in a breeze. Willis Carrier, an engineer, also observed the relationship between temperature and humidity, after waiting for a train on a foggy night in 1902. Carrier was later hired to solve a moisture problem at the Sackett & Wilhelms Lithograph Company in Brooklyn, New York. The company printed the humor magazine Judge, running each page through the press several times to apply different colors; the pressroom’s fluctuating humidity levels caused the paper to absorb moisture and expand, so the colors would not line up properly on successive print runs. Carrier remedied the problem with his Apparatus for Treating Air, which forced air across pipes filled with a cooling agent; because chilled air loses moisture, the environment became less humid. The process also dropped the ambient temperature—and the rest is air-conditioning history. Carrier’s method of forcing air across coils filled with compounds known as refrigerants is the basis of modern systems. American Heritage magazine called Carrier “a Johnny Icicle planting the seeds of climate control all across America.”