Which factor does NOT affect the efficiency of natural ventilation?

The efficiency of natural ventilation in a structure is influenced by several factors that impact how air moves through and around the building. The color of the roof surface does not directly impact the mechanics of air movement and therefore does not affect natural ventilation efficiency in a significant way.

Factors like temperature of the environment, convection currents, and wind patterns play critical roles. The temperature difference inside and outside a structure creates pressure variations that drive airflow, while convection currents rely on those temperature differences to facilitate the rise and fall of air. Wind patterns can enhance or disrupt the airflow around a building, affecting how well fresh air is drawn in and stale air is expelled.

Ultimately, while the color of the roof surface may have some indirect effects on heat absorption and radiation, it does not alter the dynamics of air movement in the way the other factors do.