What does the stack effect in attic ventilation describe?

The stack effect in attic ventilation describes the mechanism driving attic air flow. This phenomenon occurs due to temperature differences between the inside of the attic and the outside air. Warm air, being less dense, rises and escapes through vents at the top of the attic, creating a pressure differential. This results in lower pressure at the bottom of the attic, allowing cooler air from outside to flow in through lower vents.

Understanding the stack effect is crucial for effective attic ventilation, as it directly influences how air circulates within the space. Properly designed ventilation systems take advantage of this mechanism to maintain a balance in air flow, which helps prevent moisture buildup and minimizes heat retention in the attic.

The other options relate less directly to the concept of how air flows in attics. While pressure created by attic insulation may affect the overall thermal performance, it doesn’t specifically drive ventilation. Sealing an attic focuses on preventing air leakage rather than promoting circulation, and the type of ventilation used in conditioned attics refers to a design choice rather than the fundamental principle of natural air movement as defined by the stack effect.