The best HVAC system for a high-rise building depends on the size and layout of the building, as well as the climate and local weather conditions. Generally, a rooftop unit is the most efficient and cost-effective option for a high-rise building. This type of system is designed to provide efficient cooling and heating for large buildings, and can be easily installed on the roof of the building. Additionally, rooftop units are designed to be energy-efficient, helping to reduce energy costs. For buildings with multiple floors, a split system is often the best option. This type of system uses two separate units, one located inside the building and one located outside. The indoor unit is responsible for distributing air throughout the building, while the outdoor unit is responsible for cooling and heating the air. Split systems are highly efficient and can be customized to meet the specific needs of the building.