BPI Building Analyst Practice Test

The stack effect refers to the movement of air into and out of buildings due to differences in indoor and outdoor air temperatures, creating pressure differentials. This effect becomes particularly pronounced in taller buildings.

At the highest and lowest points of the building, the pressure differences are greatest due to the buoyancy of warmer (lighter) air rising and cooler (denser) air sinking. Warm air at the top of the building creates a low-pressure zone, while the cool air at the bottom generates a high-pressure zone. As a result, this pressure differential causes air to be drawn in through lower openings and expelled through upper openings. Therefore, the greatest pressures from the stack effect are indeed found at these highest and lowest points in the building.

This is in contrast to the other locations mentioned in the options. For instance, at the middle of the building, the pressure differences are less extreme since the influence of the stack effect is diminished. Entry points and air conditioning units also do not play a significant role in creating the intense pressure gradients characteristic of the stack effect observed at the top and bottom of the building.