What type of window consists of a metal frame that holds horizontal glass slats?

The type of window that consists of a metal frame holding horizontal glass slats is known as a Jalousie window. The design of Jalousie windows features adjustable slats that can be tilted open or closed, allowing for controlled ventilation while providing privacy and protection from the elements. This makes them particularly effective in hot climates, as they facilitate airflow while still keeping direct sunlight out when desired.

Hopper windows, in contrast, are known for their top-hinged design and are generally used to allow fresh air into a space while providing privacy, but they do not feature the slatted design of Jalousie windows. Skylight windows are installed in roofs to let in natural light and are not framed with horizontal slats, and storm windows are additional layers fitted to protect existing windows from harsh weather but do not have the characteristic slats of a Jalousie window. Therefore, the Jalousie window is the most accurate choice given the description.