The three basic methods for ventilating buildings are: Natural Ventilation: Utilizes natural forces like wind and thermal buoyancy to circulate air without mechanical systems. Open windows, vents, and louvers are common examples. Mechanical Ventilation: Involves the use of fans, ducts, and ventilation systems to control airflow, often used in HVAC systems for consistent air quality. Hybrid (Mixed-Mode) Ventilation: Combines both natural and mechanical ventilation to optimize energy efficiency and comfort, automatically switching between modes based on conditions.