Range Hood FAQ - Sloped/Cathedral/High Ceiling
In order to install a range hood under a sloped/angled/cathedral ceiling, or a very high ceiling, your contractor may build a "soffit box". A soffit box is a simple structure that extends downward from the ceiling, effectively lowering the ceiling height in a portion of the room. A typical soffit is made from 2x4's, covered with sheetrock and usually painted to match the ceiling.
A soffit box only needs to be large enough to provide a secure mounting point for the range hood's vertical chimney, but can be made much larger to add to the overall design of the kitchen. For example, a large soffit over the countertop provides a visual "divider" that separates the cooking area from the dining/living room, creating a design counterpoint to the island counter below.
The soffit can become a design element in its own right. For example, additional lighting, decorative trim, or a creative paint technique can be added to the soffit in order to liven up the area.