The History of HVAC: Facts for Students & Professionals

From ondol to hypocaust to “apparatus for treating air” to smart equipment, HVAC has an innovative backstory. Since before recorded history, people have tried to cool themselves when it’s hot and to keep warm when it’s cold, in one way or another.

For aspiring HVAC students and professionals, it helps to understand the roots of modern climate-control technologies. The following are the highlights of the inventors and thinkers who brought us heating, ventilation, and air-conditioning to keep us comfortable in our homes and businesses.

Early HVAC Based on the Fact That Heat Rises

We can skip the early cave fires and start with one of the earliest known attempts to control and direct fire heat in buildings. That is the Korean ondol method, which was first used thousands of years ago. It’s so efficient that it is still in use today. The famous architect, Frank Lloyd Wright, used a variation of ondol heating in some of his buildings.

Ondol heating makes use of the fact that heat rises. An outside furnace sent hot air through channels, or “gorae,” underneath the floor. The channels were constructed to direct smoke toward an opening at the far end. The floor was supported by stone pillars, and the channels were overlaid with stone slabs of mica. Mica, particularly the white variety, can withstand very high temperatures and releases heat very slowly. The floors above the channels stayed warm and cozy for hours.

Similar in principle to the ondol, the hypocaust developed by the Romans in the Middle Ages also used rising air to heat their homes and public buildings. Floors were raised by pillars about two to three feet high to make the open space beneath them. They used a continuously burning fire to create heat in the space below the floor. The Romans directed some of the hot air and smoke into vertical flues in the walls to heat them as well.

The pillars and flooring were stone, probably granite. In some installations, heat was “stored” by placing stones on top of the furnace. Radiant heat could persist for hours or even days afterward. In some houses, a “hot plate,” with small holes in it, was placed above the stones. The holes were plugged while the fire was burning. When the fire went out, the holes were unplugged, releasing smoke-free heat into the room. Hypocausts spread through most of Europe, and the remains of hundreds have been found.

The Invention of Thermometers & Later Thermostats to Control HVAC

Traditionally, people didn’t get too involved with measuring actual temperatures. Hot or cold were just part of the natural elements, like wet or dry. But in the late 1500s, Venetian thinkers began considering that heat causes air to expand and cold makes it contract. Galileo was one of these thinkers, and in the early 1600s, he invented the thermoscope, which showed changes in the degrees of heat and cold, but not actual degrees.

Although the thermoscope had little practical use, it led to the development of thermometers by others. Unfortunately, each inventor used his own scale of degrees. Each also used different kinds of liquids to make his measurements. In 1714, a German physicist named Daniel Fahrenheit invented the mercury thermometer and the Fahrenheit scale still in use today. Anders Celsius, a Swedish astronomer, invented the Celsius, or Centigrade, thermometer. He used pure seawater at sea-level pressure to determine its boiling point at 100 degrees Celsius.

William Thompson (Lord Kelvin) invented the Kelvin Scale years later to measure absolute zero, the temperature at which everything, including air, freezes. Kelvin used the Celsius scale, but modified it so that Kelvin zero is absolute zero, or minus 273 degrees centigrade. These early devices led to the thermostats used to control HVAC and comfort levels today.

Gorrie’s Ice Machine: Rudimentary HVAC Refrigeration

In the 1800s, a young physician, physicist, and inventor named John Gorrie settled in Florida. As a doctor, he was concerned about yellow fever and malaria, which took many lives. He also became mayor of the port city of Apalachicola and set to work draining the swamps. As scientists had not yet discovered the link between mosquitoes and malaria, Dr. Gorrie believed that fevers resulted from vapors in the hot tropical air of Florida. He devised an “air conditioning system” that blew air over buckets of imported ice into the sickrooms to reduce fevers.

He further refined his system into an ice machine for which he was eventually granted patent #8080. However, at the time, ice houses were big business, and the operators ridiculed Gorri’s invention so vehemently that all his financial backers withdrew their support. Despite that, his ice machine, which produced both ice and cool air, was used in the first air-conditioned hospital ward. “His process was the predecessor of the compressed-air ice-making machine used almost universally aboard ships in the early twentieth century.”

Gorrie was never able to secure adequate financial support, and he died early, discouraged and financially broken. He was the designer and builder of the first refrigeration machine for comfort cooling, and was regarded by some as the father of air conditioning as we know it today. However, he remains unknown to most people.

Carrier Wanted to Reduce Humidity, but Developed Modern HVAC

A New Yorker named Willis Carrier is widely regarded as the father of air conditioning. Carrier was an engineer employed by Buffalo Forge Company, where he drafted plans to heat and dry various products for clients. He was tasked with solving the problem of humidity causing paper to wrinkle and ink to smear at a publishing company. The company needed precise control of the humidity. After trying an experiment recommended by the company, Carrier resorted to his own creativity.

He devised a system that used cold water flowing through metal coils to balance the temperature of the coils and modify the air temperature. Although the system needed fine-tuning, the first set of coils, fans, ducts, heaters, perforated steam pipes, and temperature controls was installed in 1902. The system was designed to maintain a constant humidity of 55 percent, and it did so wonderfully well.

Carrier’s inventive genius led him to eventually become head of the Buffalo Forge Company, where he directed research and design. His “Apparatus for Treating Air,” which he patented, was only one of his designs for creating customized humidity levels and air temperature for various companies. His successes led Buffalo Forge to establish a subsidiary, Carrier Air Conditioning Company of America. That company was closed down at the start of WWI.

Willis Carrier, along with other engineers, incorporated Carrier Engineering Corporation in 1915 (later renamed Carrier Corporation). Much of the company’s early business involved war effort contracts. After the end of the war, the company continued to sell products advertised as “Manufactured Weather for any requirement.” Carrier continued to innovate, and in 1922, he brought to market the centrifugal chiller. The company has only continued to grow in HVAC and refrigeration since then.

Window Air Conditioners and Central Air Conditioning are the Basis of Today’s HVAC

By the 1930s, people wanted comfort cooling in their homes. Several inventors, including those associated with Frigidaire and General Electric, developed “room coolers” that were small enough for homes but were heavy, expensive, and difficult to operate. They never found a market.

H.H. Schultz and J.Q. Sherman invented a smaller room cooler that could be set on a window ledge. However, they were so expensive that only the wealthy could afford them. Henry Galson, an Austrian engineer, developed a smaller and less expensive window air conditioner. Sales took off, and by 1947, homeowners had purchased 43,000 units.

Although Carrier’s early air conditioners were used in large commercial buildings, such as movie theaters, advances in refrigeration technology and the growth of mass production enabled the equipment to be downsized to fit in residences. By the 1950s, reduced cost and size, increased efficiency, and the development of ductwork led to the installation of central air conditioning units in homes. Although millions of homes now have central air conditioners, window air conditioners remain popular.

The inventors noted above not only used their own creative abilities and engineering knowledge, but also drew on dozens of small innovations and improvements by others. Up-and-coming inventors will continue to build on these and improve technology to design the HVAC systems of the future.

Sandra Smith

Sandra Smith was introduced to the HVAC industry when she worked as a bookkeeper and secretary for a small air-conditioning contractor. She eventually became a CPA and started her own practice specializing in small business taxes and accounting. After retiring from business, she began writing articles for newspapers, magazines, and websites. She also authored four books. Sandra makes her home in the mountains with a rescue dog that naps on her lap as she writes.