HVAC design includes the selection and sizing of all components of the system, including the air handler, ductwork, and other components. It also includes the selection of the appropriate type of system, such as a split system, packaged system, or rooftop unit. Additionally, HVAC design includes the selection of the appropriate type of refrigerant, the selection of the appropriate type of air filter, and the selection of the appropriate type of insulation. Finally, HVAC design includes the selection of the appropriate type of controls, such as thermostats, zoning systems, and humidistats. All of these components must be carefully selected and sized to ensure the system is efficient, reliable, and cost-effective.