With systems dating back into the 1800s, hydronic heating has been around a long time. As with many technologies, a modern hydronic heating system bears little resemblance to one based on the earliest design techniques and hardware. Imagine explaining the concept of a circulator to a design engineer from 1900 who might only know of electricity as something a few scientists experiment with. Think about convincing an engineer of that era that pipes capable of lasting well over 100 years could be made of materials derived from oil.
Hydronic systems were the “norm” in many buildings prior to the availability of central cooling systems, which began entering the U.S. market in the late 1950s. Central cooling was indeed a “game changer” for the U.S. thermal comfort market. It shifted focus to forced air distribution systems, which could deliver that highly anticipated cool/dry air in summer, as well as heated air in winter.