Windows – Name of a projection window used to admit more light and air Which type of window projects outward from the face of a room to enlarge the interior space and increase the admission of light and air into the building?

Introduction / Context:
Window types are distinguished by their geometry and operation. Some enhance ventilation and daylighting by projecting beyond the wall line, while others are defined by their hinge mechanism or roof placement. Identifying the correct term is important for architectural drawings and BOQs.

Given Data / Assumptions:

• The window projects outside the external wall plane.
• Purpose is to admit more light and air and to increase view area.
• Typical in residential façades and bays.

Concept / Approach:

A bay window projects outward, forming a bay inside the room. It can be polygonal, square, or semicircular, often combining multiple sash units. A casement window is side-hinged and does not imply projection beyond the wall. A dormer window projects from a sloping roof surface, not from a wall. A lantern (roof lantern) is a glazed structure on top of a roof to admit light from above. Thus, the projection from the wall for more light and air is a bay window.

Step-by-Step Solution:

Verification / Alternative check:

Architectural manuals define bay windows as projections increasing light, ventilation, and interior niche space, commonly supported by brackets or cantilevers.

Why Other Options Are Wrong:

Casement describes hinge action; dormer and lantern are roof elements; pivoted describes rotation mechanism, not projection.

Common Pitfalls:

Confusing bow windows (curved plan) as a different category—both are bay types; assuming any outward-opening sash is a bay.

Final Answer:

Bay window