Which of the five comfort requirements has the greatest effect upon temperature stratification within a room?

• A. Circulation
• B. Filtration
• C. Humidity
• D. Ventilation

Answer: (A)

Temperature stratification happens when warm air rises and cool air stays near the floor because there isn’t enough air movement to mix the layers. The factor that most directly controls how much mixing occurs inside a room is circulation—the movement of air within the space. When circulation is good, air currents carry heat from the ceiling downward and pull cooler air upward, blending the layers and making the temperature more uniform throughout the room.

Filtration mainly removes particles and doesn’t drive mixing. Humidity can subtly affect air density but doesn’t produce strong vertical mixing. Ventilation exchanges indoor air with outdoor air and can change overall temperatures, but its effect on the in-room vertical temperature gradient is secondary to how well the room’s own air is circulated. Therefore, circulation has the strongest impact on reducing temperature stratification.