ASME-Landmark:Milam High-Rise Air Conditioned Building

The Milam Building was the first high-rise air-conditioned office building in the United States. The air-conditioning design team was led by Willis H. Carrier, founder of the Carrier Engineering Corporation, in cooperation with architect George Willis, engineer M.L Diver, and contractor L.T. Wright and Company. The system provided 300 tons of refrigeration capacity with chilled water piped to air-handling fans serving all floors. The original unit has been updated and modernized since its installation.

When it opened in January 1928, the 21-story Milam Building was also the tallest brick and concrete-reinforced structure in the United States. Stores, auditoriums, and theaters had been air conditioned earlier, but high rises require air conditioning to be part of the original design in order to allow for ducting as well as air handling and control equipment.

Carrier's air-conditioning design team studied local weather bureau records and the sensitivity of San Antonians to determine comfortable atmospheric conditions, deciding on a maximum indoor summer temperature of 80 F with a relative humidity not exceeding 55 percent; in winter, their target temperature was 70 F or above with a relative humidity of 45 percent. Further factors adding to the complexity of the design included heat-generating exposure, such as the problem of radiant heat from the sun as it traveled from one side of the building in the morning to the other in the evening. Good air distribution, the re-use of return air, air-leakage concerns, and individual control were other design considerations. See ASME website for more information