What percentage of opening do casement windows provide in the ventilator area?

Casement windows are designed to provide maximum ventilation when fully opened. When you open a casement window, the entire area of the window becomes available for airflow, which means that the ventilator area is effectively 100% of the window opening. This design allows for a full and unobstructed passage of air, making casement windows particularly effective for controlling indoor ventilation and improving air quality.

The correct answer reflects the fact that the nature of casement windows, which pivot open from one side, allows them to create a larger opening compared to other types of windows, where the percentage of the opening might be limited due to design features like sashes or frames that restrict airflow even when the window is open. This distinct characteristic is significant in both residential and commercial applications, especially where ventilation efficiency is critical.