HVAC In The 1940s

By Jim Olsztynski

The HVAC trade in the 1940s scarcely existed as we know it today. Although air conditioning had been invented by Willis Carrier way back in 1902, the earliest systems were too bulky, noisy and expensive to make much headway in the residential market. Window units, deemed “room coolers,” were invented in the 1920s, but they cost what would amount to thousands of dollars in today’s money and were installed only in the wealthiest homes.

Prior to the 1950s, central a/c was limited almost entirely to commercial and industrial buildings. Movie theaters were a favorite market, offering Depression-era patrons a few hours of entertainment and relief from oppressive summer heat. Old-timers can recall ubiquitous posters outside of movie theaters depicting a fan blowing over an ice block, with bold letters advising, “It’s cool inside!” Those commercial-industrial systems typically operated via water-based chillers, with the work done by union pipefitters.

Heating at the dawn of the 1940s was delivered mostly by stream and hot water boilers, so-called “hydronic heating,” and it was an offshoot of the plumbing and pipefitting trades. Coal-burning furnaces heated about half of American households in 1940, with around a quarter relying on fuel oil and the rest mainly on wood. Wood stoves and fireplaces were especially common in the South, which until post-WWII was an economic backwater, largely because of its oppressive summer heat.

Air conditioning got a boost during the war years from its technological cousin, refrigeration. In 1940 an inventor by the name of Frederick McKinley Jones was issued a patent for a roof-mounted cooling device that would refrigerate the inside of a truck. This device was soon adapted for use on trains and troop ships to provide our soldiers with fresh provisions.

Wartime necessity was the mother of many advances in refrigeration and a/c technology during the mid-1940s. More and more offices and factories installed air conditioning because of studies showing a proven link to increased productivity, a worthwhile investment given the massive demands for wartime goods. But these technologies were expensive and largely unavailable to the average home. Household names like Trane, York, Lennox and Carrier went to work building heating, cooling and refrigeration systems for military facilities, ships and planes.

During this era much research was being done on forced-air HVAC systems, which over the next half-century would eventually come to replace most hydronic systems in the residential and commercial markets. So the HVAC trade as we know it today can be traced to the postwar era starting in the late 1940s.

Postwar America: By the time the war ended, many existing home heating systems were on their last legs due to lack of maintenance and spare parts during the war years. Residential plumbers did a lot of business fixing and replacing boilers and their components, but the real action took place with a new housing boom triggered by pent-up demand and plenty of households with money to spend from wartime savings and G.I. Bill mortgage guarantees. Along with new homes they bought refrigerators and window air conditioners.

In 1947 only around 43,000 window air conditioners were sold, but that number would grow to 1.45 million by 1953, Many early HVAC technicians got their start installing and repairing those window units. It would take a few more decades before unitary central air systems became widespread. Even by 1970, only an estimated 11% of American homes had central HVAC.

One problem delaying progress was a shortage of refrigerant gases. It took several years beyond the end of WWII for supply to catch up with demand. Also, with housing in short supply it was easier and less expensive to fit them with tried-and-true hydronic heating rather than a technology unfamiliar to installers. But as the years and decades passed central HVAC underwent a dramatic market turnaround that would see it surpass hydronic heating as the system of choice in more than 90% of new homes built. Its main attraction, of course, is the ability to provide both heating and cooling at the flick of a switch.

Heat pumps also began to get a boost during the late 1940s. Refrigeration engineers had long known about the reversibility of refrigeration technology to provide heat and well as cooling, but this, too, was an unfamiliar technology to most early HVAC technicians. The need to quickly build homes for all those returning soldiers and their families discouraged innovation in the early postwar years.

Central HVAC continued to make inroads during the ensuing decades and by the 1990s unitary HVAC and heat pumps were dominating the new construction market. Along the way, air conditioning is credited as one of the main factors opening up the Sunbelt to development. Prior to a/c, the South was mostly rural and poor due to heat and humidity that drained productivity from even the hardest of workers. Now, the Sunbelt regions are attracting millions of northerners looking to escape oppressive winters!

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