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Weston Urban

The First Office Tower Air Conditioning System Designed by Willis Carrier Himself

There are many famous buildings, renowned for their engineering feats or revered for their historical significance. But some important buildings don’t have the kind of notoriety that they rightfully deserve. Despite their significance to our cultural and scientific history they remain relatively unknown except for some local fanfare. The Milam Building in downtown San Antonio is one of these.

Built right before the great depression hit in 1929, the twenty-story building was the first highrise built without steel girders, using reinforced concrete instead. More important than its structural reinforcement were its mechanical systems. The Milam Building was the first air-conditioned highrise building in the world. Plenty of other buildings already had air conditioning, mind you. Things like shops and theaters were already using air conditioning to draw in customers quite successfully. But until the Milam Building was built, no one had connected the dots about what it would mean for the value of an office building.

The hulking, 210,000 square foot neo-gothic Milam Building was intended to be a monument to the state of Texas. It was named after one of the heroes of Texas’s war with Mexico and to this day the only flag that flies above it is for the Lone Star State. It was also intended to give its occupants a respite from the punishing South Texas heat. 

The architect for the building was George Willis, former head draftsman for Frank Lloyd Write. The look of the building is rather muted, especially compared to the other highrises being built at the time, but Willis wanted to push the envelope not with the building’s architecture, but its functionality. So he employed Willis Carrier, the original inventor of the air conditioning system, which was created not to cool down humans but rather to help printing factories control their humidity. 

Originally installing “Carrier’s Manufactured Weather,” as it was called at the time, in the building was touted for its health benefits. Installing a cooling system allowed occupants to keep its windows closed in the summer, reducing the amount of dust and pollution that would come in from the street outside. (Little did they know that this same outside air would later be seen as the solution to poor internal air quality, not the cause of it.)

If you think adding air conditioning to a tall building seems like an easy task then you obviously do not design HVAC systems. To make things more complicated, since the practice of cooling offices was so new, every lesson about how to cool a highrise had to be learned on the spot. Before Carrier even designed the system he had to first understand how cool he would even need to get the building. He studied local San Antonians to see what weather conditions they considered comfortable, knowing that every degree he needed to heat or cool the building would come with enormous energy and equipment costs. Finally he settled on a temperature that would be downright unbearable to us spoiled 21st century workers. He guaranteed that the building would not exceed 80 degrees Fahrenheit and 55 percent relative humidity even in the hottest part of the summer.

To do this he installed massive chillers in the basement of the building. These giant machines pumped out over 300 tons of refrigeration and originally used river water and were assisted by placing large blocks of ice next to them in the basement. The building also uses a large water chilling tower that can help cool the building even if the chillers fail. In order to get the cold, heavy air from the basement all the way to the top floors, which are generally the hottest, Carrier had to bring in a special pump from Germany that was used to circulate air in mine shafts. 

One of the hardest challenges Carrier and his team faced was what they called the “traveling sun.” Unlike shorter buildings, a tower absorbs a lot of heat from the sun shining on its side. Not only does this increase the temperature in the building, it does so in an uneven way. The side of the building that is exposed to the sun also changes with the season, making it an even harder to design a system that would disburse the cool air to where it was most needed. To combat this effect, The Milam Building was equipped with special window blinds, adjustable air dampers, and a plethora of thermostats throughout the building. Sometimes the temperature was so uneven that the building engineers would have to heat the overchilled areas. Inefficient, I know. For decades the Milam Building was one of the largest, if not the largest, consumers of power in all of San Antonio. 

Despite the inefficiencies by today’s standards the system worked well. It ran continuously all the way until it was replaced in 1989, a project that was celebrated. It also sparked a new era of office comfort. After word of the Milam Building spread Willis Carrier was commissioned to install a manufactured weather machine on a train  for a rail tycoon and in the oval office for President Hoover. Offices that invested in cooling systems eventually came to command a 15 percent premium, a financial incentive that almost every building owner was eager to take. 

So if you go to San Antonio, pay homage to the building that pioneered the comfortable workplace. Or, maybe even better, just sit in front of an AC vent and think about how lucky you are to not have to work in an office in South Texas before 1929.

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