On this page you will find a glossary of many home-improvement terms.
Click on a letter below to go to that section, or just scroll through the terms to find your definition.
Argon is a safe, odorless, colorless, non-toxic, non-flammable inert gas that is commonly used in place of air between the glass panes of an insulated Low-E glass unit to reduce temperature transfer.
A composite of three windows, usually made up of a large center fixed unit and two flanking units at 30°,45° or 90° degree angles to the wall.
A composite of four or more window units in a radial or bow formation.
A window unit in which the single sash cranks outward, to the right or left.
Molding of various widths, thickness and shapes applied to the framework of window and door units.
A mastic compound for filling joints and sealing cracks to prevent leakage of water and air, commonly made of silicone, bituminous, acrylic, or rubber-based material.
Energy transfer from one material to another by direct contact.
Heat transfer by currents that flow from a warm surface to a colder one.
A window unit that has two operable sashes which move vertically in the frame.
Double or Dual Glazing
Use of two panes of glass in a window to increase energy efficiency and provide other performance benefits.
An architectural term referring to the arrangement of windows in a wall. From the Latin word, “fenestra,” meaning window.
A composite material made by embedding glass fibers in a polymer matrix. May be used as a diffusing material in sheet form, or as a standard sash and frame element.
Non-venting or non-operable window. Also known as picture window.
A plastic or wood strip applied to the window sash around the perimeter of the glass.
A combination of two or more panes of glass with a hermetically sealed air space between the panes of glass. This space may or may not be filled with an inert gas, such as argon.
A common term used to refer to glass which has low emissivity due to a film or metallic coating on the glass or suspended between the two lights of glass to restrict the passage of radiant heat.
Any small bar that divides a windows glass. Also called a grille or windowpane divider.
The top and bottom horizontal members of the framework of a window sash.
Resistance to thermal transfer or heat flow. Higher R-value numbers indicate greater insulating value.
A single assembly of stiles and rails made into a frame for holding glass.
A flat board cut to fit the contour of a bow or bay window and installed between the sills and the flat wall surface, providing a seat or shelf space.
The main horizontal member forming the bottom of the frame of a window or door.
Simulated Divided Lite
A method of constructing windows in which muntins are affixed to the inside and outside of a panel of insulating glass to simulate the look of true divided light.
Use of single panes of glass in a window. Not as energy-efficient as double glazing.
A double-hung type of window in which the top sash is fixed or inoperable.
Both sashes slide horizontally in a double-sliding window. Only one sash slides in a single-sliding window. Ventilation area can vary from a small crack to an opening of one-half the total glass area. Screens can be placed on the exterior or interior of the window unit.
The main vertical members of the framework of a sash.
An interior trim piece on a window which extends the sill and acts as a narrow shelf.
A molding used to hold, position or separate window parts.
Glass manufactured to withstand greater than normal forces on its surface. When it breaks, it shatters into small pieces to reduce hazard. Standard on all doors and large fixed windows.
True Divided Lite
A term which refers to windows in which multiple individual panes of glass or lites are assembled in the sash using muntins.
A measure of air-to-air heat transmission (loss or gain) due to thermal conductance and the difference in indoor and outdoor temperatures. As the U-Value decreases, so does the amount of heat that is transferred through the glazing material. The lower the U-Value, the more restrictive the fenestration product is to heat transfer.