casement

A casement is a window or door hinged on one side that opens outward or inward. The moveable panel is called the sash; opening is achieved by a crank, handle, or lever.

Operation and seal: When closed, the sash presses against weatherstripping along all sides, creating a tight seal that improves energy efficiency and weather resistance. The design allows wide clear views.

Materials and glazing: Casement frames are made in timber, uPVC, aluminum, or composites. The sash often contains double or triple glazing; optional low-emissivity coatings and inert gas fills enhance insulation. Some casements incorporate divided lites for traditional appearances.

Advantages and limitations: Benefits include unobstructed sightlines, robust sealing, good ventilation, and ease of security with locking hardware. Limitations include the need for exterior clearance to operate, potential hardware wear, and maintenance considerations for timber frames. They may be less suitable for small rooms or windy locations where the sash could catch.

Applications and history: Casement windows have long been used in European architecture and modern housing. They are common in renovations of heritage buildings and in new construction where large, unobstructed openings are desired. Variants include side-hinged casements, top-hung auxiliary vents, and multi-casement assemblies, sometimes integrated with tilt-and-turn mechanisms.