Which of the following are the two main types of HVAC systems?

The two main types of HVAC systems are central and decentralized systems. Central systems are designed to control the temperature and air quality for multiple spaces or an entire building from a single, centralized unit, typically using ductwork to distribute heated or cooled air. This includes systems like central air conditioning and central heating. Decentralized systems, on the other hand, serve individual spaces with self-contained units, such as window air conditioners or ductless mini-split systems. Each type has its own benefits and applications depending on the specific needs of the building or area being serviced, making this classification fundamental to understanding HVAC functionality and design principles.

Other choices focus on different aspects, such as energy sources or building types, which do not classify HVAC systems in the same primary manner. Therefore, while they may be important categories in other contexts, they do not represent the two main types of HVAC systems.