Casement window

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Casement window, with latticed lights.

A casement window (or casement) is a window that is attached to its frame by one or more hinges.[1] Casement windows are hinged at the side. (Windows hinged at the top are referred to as awning windows. Ones hinged at the bottom are called hoppers.) They are used singly or in pairs within a common frame, in which case they are hinged on the outside. Casement windows are often held open using a casement stay.

In the UK, casement windows were the most common house window before the sash window was introduced, and usually contained leaded glass - glass panes held in place with strips of lead (called lead "cames"; leaded glass is not to be confused with lead glass, which refers to the manufacture of the glass itself).[2] These casement windows usually were hinged on the side, and opened inward. The windows were covered by functional exterior shutters, which opened outward. Variants of casement windows are still the norm in many European countries, such as Denmark and Sweden.

They are opened with a crank, lever, or cam handle, which is placed around hand height or at the bottom and serves as a window lock.[3] A crank, stay, or friction hinge is necessary when the window opens outward, to hold the window in position despite wind.

Often the glass panes are set in a rabbeted frame and sealed with beveled putty or glazing compound to secure the glass.

Modern casement windows are excellent to prevent air leakage[edit]

Modern casement windows close tightly, and they use compression seals, which minimizes air infiltration. Their operation system – based on compression seals and hinges – provides a much lower air leakage than double-hung and gliding windows. They are the best window design for energy improvements and energy efficient buildings.[4]

Casement windows weatherstripping[edit]

The exact type of weatherstrips used by casement windows varies a lot. Dual compression seal systems with multiple locking points around the perimeter are excellent for performance. But whatever the type of weatherstrips, casement windows provide a better sealing than common sliding windows or traditional double-hung windows (horizontal sliding windows may have the worst air leakage performance).[5]

Casement windows and natural ventilation[edit]

Casement windows are also excellent for natural ventilation strategies, especially in hot climates. They can be hinged to open outward and angled in order to direct breezes into the building.


  1. ^ Poppeliers, Chamers, Jr.; Schwartz (1983). What Style is it?. NY: John Wiley and Sons. p. 98. ISBN 0-471-14434-7. 
  2. ^ "Casement window". Illustrated Architectural Dictionary. Archived from the original on 2007-12-24. Retrieved 2008-01-18. 
  3. ^ Ching, Francis (1997). A Visual Dictionary of Architecture. New York: Van Nostrand Reinhold. pp. 113, 116, 273. ISBN 0-442-02462-2. 
  4. ^ “What's the range of window air leakage values";
  5. ^ “Casement Windows & Weatherstripping";