What term describes the pressure difference created by a vent or chimney due to height and temperature differences?

The correct term that describes the pressure difference created by a vent or chimney due to height and temperature differences is natural draft. Natural draft is the result of the buoyancy effect, where warmer air inside the chimney or vent rises because it is less dense than the cooler air outside. As the warm air exits, it creates a pressure difference that draws fresh air into the combustion chamber or appliance.

This mechanism is fundamentally tied to the principles of thermodynamics and fluid dynamics. When the temperature of the air inside the vent or chimney rises due to heat from combustion, it expands and reduces its density. The difference in density between the warm air and the cooler outside air leads to a natural upward flow, allowing for adequate ventilation or exhaust without the need for mechanical assistance.

Understanding natural draft is crucial for HVAC professionals, as it impacts the efficiency of heating systems and the safe operation of appliances requiring ventilation.