Hospitals use 2-3 times more energy than other commercial buildings. And HVAC energy is 2/3 to 3/4 of their energy use. Heat energy is the largest consumption and much of it goes to ventilation requirements and air changes per hour rates (ACH).
Until 1800s, people believed that diseases came from polluted air such as malaria (malaria in Italian means bad air). Until Louis Pasteru introduced the idea of microorganism. Many diseases belived to be airborne, such as cholera, chlamydia, etc, do not transmit via air. So by early 1900s, the public health and medical communities started to put less emphasis on air as the main cause of diseases. This has affected the hospitals and their indoor climate.
Source: ASHRAE Journal June 2016 by Travis R. English