WIndow Glossary

Argon:  A gas that insulating glass units are filled with in order to reduce the loss of heat or cooling via radiation or conductive heat.  Argon gas also will help to soundproof your home.

Awning Window: Same as a casement window except the sash is hinged at the top section and projects outward.

Bay Window: Three or more individual window units arranged in such a way that the window projects from the structure or home at various angles. In a three unit bay window, the center section is normally fixed with the end panels functioning as single hung or casements.

Bow Window:  A bow window is normally arranged with three or more equal-width units.  They are usually mulled together with a angle such as thirteen degrees.


Casement Window:  A single unit of glass in most cases longer vertically than horizontally.  It can be opened ot to outside or inside.

Double Window:  Windows that use two thicknesses of glass,separated by a space of air.  This improves insulation and greatly helps in soundproofing your home.

Energy Star:  The energy star label was actually created by the U.S. government (The Environmental Protection Agency/EPA) to help consumers more easily identify those windows, doors, and skylights that provide the best levels of energy and cost efficiency.

Fixed Window:  A stationary window such as a picture window.

Float Glass:  Glass which has its bottom surfaces carefully formed by floating on a surface of molten metal. The top surface is gravity formed and produces a high optical qualify of glass with surfaces that are parallel.  This produces the finest quality of sheet glass.

Hopper Window:  This is similar to a casement window except the sash is hinged at the bottom

Horizontal Slider Window:  A window in which the moveable panel slides in a horizontal fashion.

Insulating Glass:  This refers to two pieces of glass spaced a certain distance apart and acting to hermetically seal the glass, thereby forming a single-glazed unit with a space between. Heat or cooling loss for insulating glass is typically one half as much as a unit without an insulating air space.  This is also known as double glazing.

Jalousie Window:  This type of window is comprised of horizontally mounted louvered glass that touch each other securely when closed and extend outword when cranked to the open position.

Low-E:  Low emissivity, Low-E glass products receive a coat of microscopic, thin optically transparent layers of silver, sandwiched between layers of anti-reflective metal oxide coatings.  In the summer Low-E windows allow visible sunlight to come in while blocking infrared or ultraviolet light that makes it more expensive to cool your home, and can also cause your home furnishings to fade. In the wintertime, Low-E glass provide greater comfort and reduce your overall heating costs by reflecting the heat of your home off of the windows back into your home.

Mullion:  A connective device used to join two or more windows or patio doors together in a single rough opening with giving up air or watertight qualities.

Muntins:  A decorative design for glass lites.

Picture Window:  A stationary window that is usually longer horizontally to provide a panoramic view.

Plate Glass:  Glass that is rolled, ground and polished and provides excellent vision. 

Sash of Window:  The section of the window that includes the glass and the framing sections that are  directly attached to the glass.  This is not to be mistaken for the master frame into which the sash sections are fitted.

Single Hung:  Similar in look to Double Hung window, the single hung window has a stationary top and a moveable bottom half.

Slider Window:  This type of window has one or two moveable panes of glass sliding horizontally.

Spacer Shims:  Devices that are shaped like "U"s in cross-sections and placed on the edges of lites or panels to act as both shims and spacers to keep the lites or panels centered in the sash or frames as well as the window channels.

Stile: The upright vertical edges of a window or screen (also door).

Storm Windows:  A second set of windows installed on the outside or inside of the main windows to provide additional insulation in extreme climes.

Tempered Glass:  Tempered glass is re-heated to just below the melting point, then suddenly and rapidly cooled.  When this type of glass breaks, it shatters into small pieces . It is approximately five times stronger than standard glass.  It must be used as safety glazing for patio doors, entrance doors, and other hazardous window locations.

Thermal Break:  An element of low conductivity placed between the elements of higher conductivity to reduce the loss of heat or cold, thereby providing insulation.

Tilt Window:  A single or double hung window that can be tilted into the room for interior washing.

Tinted Glass:  A mineral mixture that adds a tint to glass that will somewhat reduce visual and radiant qualities.

Unit:  A term typically used to express a single lite of insulating glass.

U-Value:  The measurement that is used to determine the ability of structures (such as windows) to conduct heat.  The U-Value of a window is measured by the number of BTUs that will pass through each square foot of area per degree of temperature variance from one side of the window to the otherd. U-Values are an indication of how well your windows will hold in your cooled or heated air.  The lower the U-Value the better.