What phenomenon occurs when cool air enters the lower levels of a building and warm air rises?

The phenomenon described in the question is known as the Stack Effect. This occurs when there is a temperature difference between the inside and outside of a building, causing cooler air to enter from the lower levels while warmer air rises and exits from the upper levels.

In this scenario, the warm air inside the building, being less dense, rises and escapes out of vents or openings at higher levels, creating a lower pressure at the bottom, which subsequently allows cooler, denser air from outside to enter at the lower levels. This natural movement of air is influenced significantly by differences in air density due to temperature, effectively creating a stack-like action.

In contrast, convection refers more generally to heat transfer through fluid motion and is not specific to the vertical movement of air in buildings. Pressure differentiation pertains to varying pressure levels but does not directly encompass the specific temperature-driven air movement described in the question. Thermal inversion involves a situation where warmer air traps cooler air below it, which is the opposite of what is happening in the Stack Effect.