There’s a good chance that you’ve not only heard the terms windowsills and windowpanes but that you also know what they are. However, do you know the meaning of other window-related terms, such as aprons, mullions, and jambs? If not, this Window Terminology Guide is for you.
In this guide, we’ll provide you with a basic understanding of replacement window terminology. Equipped with this knowledge, you’ll be able to properly care for your windows throughout the year. Additionally, you’ll be able to better communicate with your window contractor and determine which window options are right for you.
Complete List of Window Terminology
Below is a comprehensive list of the most commonly used replacement window terminology.
Apron: An apron is a piece of decorative trim placed directly against the wall and right under the stool of the window.
Casing: Also referred to as casement molding, the casing is a decorative frame around the entire window. It’s used to fill in the gap between the wall and the window jamb or frame.
Frame: The window frame consists of the windowsill, jambs, and header. It’s attached to the window to provide extra support for the window system.
Glass Package: This energy-efficient window option typically uses two or three glass panes that are precisely spaced apart. These panes are held in place using spacers or by grooves in the sash of the window. This careful placement helps to provide an air-tight seal.
Header: The header is a beam located at the top of the window casing. It’s typically wider than the window frame and spans the length of the top portion of the window. It’s used as a supportive feature to prevent the full weight of the wall surrounding the window to put pressure on the glass panes.
Jambs: Typically made of wood or vinyl, jambs are the vertical pieces located on the sides of the frame of the window.
Jamb Liner: These are strips placed on the sides of a window to ensure the glass panel fits tightly into the window sash.
Mullions and Grilles: These thin pieces of wood, vinyl, or wood are placed directly on the windowpanes. Mullions help to provide the visual appearance of multiple windowpanes. However, the panes themselves are not actually divided.
Rail: This is the horizontal part of the window where the upper and lower sash parts meet.
R-Value: This measurement is used to rate the ability of insulation to resist heat. The higher the R-Value on the scale, the better the insulation will perform.
Sash: The sash is the horizontal and vertical frame that’s used to actually hold the windowpane in place. The number of sashes depends on the type of window. For example, a double-hung window will have both an upper and lower sash that meet together at the rail, while a single-window will only have one sash.
Stool: Commonly called the sill, the stool starts at the bottom of the sash and extends inward.
U-Factor: Unlike the R-Value, the U-factor is used to rate the level of heat loss through the window. The lower the rating, the more energy-efficient the window is because it’s better able to resist heat loss.
Weather Stripping: This critical component is used to reduce the risk of air and water leaks. The material is used to cover the upper and lower portions of the sash.
Weep Hole: A small hole in the windowsill placed specifically to allow water and condensation to safely drain outside your home, the weep hole helps to prevent damage to the windowsill, sash, and frame.
Window Stop: This narrow strip helps to hold the window sash at a set position in the window frame.
Having knowledge of basic window terminology will help you make informed decisions about which window options are best for your home or business. To learn more about replacement window technology and services, contact Thompson Creek Window Company today.