Windows Glass and Fenestration 101

When shopping for windows, you will face several choices regarding the style and type of window you want. This page provides an introduction in to the common styles and choices you will face — and provides visual “descriptions” so that you can have a thorough understanding when making such important decisions for your home.

Single-hung means that one of the windows sashes is fixed  in place and does not move.

Single-hung means that one of the windows sashes is fixed in place and does not move.

Double-hung means that both sashes in a frame are  operable.

Double-hung means that both sashes in a frame are operable.

Awning Window: A window that opens from a top hinge and projects outward.
Casement Window: A window containing one or more side-hinged openings that open either outward or inward. A conventional casement window has a sash that projects outward.
Dual Action Window: A window that operates in two different ways — typically, the window consists of a sash that may tilt from the top or may swing inward from the side.
Greenhouse/Garden Window: A window unit that consists of a three-dimensional, five-sided structure generally protruding from the wall in which it is installed. The window may or may not open.

Hinged Escape / Rescue / Egress Window: A window that opens wide enough to allow escape from inside (and entrance for rescue workers). Many building codes require egress windows in all bedrooms that do not have doors that exit the building. For example, a basement room can not be described as a “bedroom” unless there is an egress window (and large enough window well) or door to the exterior of the building. Please check your local codes for additional requirements.

There are many varieties and styles of egress window, some of which operate differently than the example shown. It is important for all family members to understand how the egress windows work; fire drills are recommended.

Storm Window: A glazed window attachment product designed to be mounted to the inside or outside of a window to create an air space between the window and the storm window. This is sometimes called an “energy panel.”
Transom: A non-operable window that is often installed above either another window or a door. Transoms may consist of a glazed frame or a non-operable sash within a frame.
Tubular Daylighting Device (TDD): A non-operable device primarily designed to transmit daylight from a roof surface to an interior ceiling surface via a tube. The device consists of an exterior glazed surface, a light transmitting tube with a reflective inside surface, and an interior sealing device, such as a translucent ceiling panel.
Skylights: In addition to the Tubular Daylighting Device shown above, skylights may also be flat panels (similar to a regular windows) but designed to perform on an angle or flat (depending on the roof surface), and they may be operable or non-operable. There are additional designs for skylights, but the purpose of all is to provide additional natural daylighting into the building.