Complex sentence: Central heating had existed since the 18th century, but could not be easily extended to serve larger buildings; in the 1850s, a system using low-pressure steam and steam-operated fans became adopted in the construction of the later skyscrapers.
Split into simpler sentences: Central heating had existed since the 18th century, but could not be easily extended to serve larger buildings. In the 1850s, a solution was found using low-pressure steam and steam-operated fans, which was quickly adopted in the construction of the later skyscrapers.