Natural ventilation relies on which forces to deliver fresh air into a building?

• A. Wind and buoyancy
• B. Mechanical ventilation
• C. Heating coils
• D. Filtration systems

Answer: (A)

Natural ventilation relies on air movement driven by environmental pressure differences, specifically wind and buoyancy (stack effect). When wind hits a building, it creates higher pressure on the windward side and lower pressure on the opposite side, pushing air in through openings and pulling it out elsewhere. Inside the building, warm air is lighter than outside air, so it rises and escapes through upper openings while cooler outdoor air is drawn in through lower openings. This combination of wind-induced pressure and buoyancy moves fresh air through the space without mechanical help.

Mechanical ventilation uses fans and ductwork to move air, which is not natural ventilation. Heating coils don’t drive air movement for ventilation, and filtration systems clean air but don’t create the airflow needed to bring in fresh outside air.