Here at Rescom, we want to make the window replacement process as simple as possible for our clients. That is why we’ve put together this handy window glossary. When you turn to us for replacement windows in Auburn or any of the surrounding areas, you’ll hear us use many of these terms. By offering this glossary we hope to educate local homeowners on their windows, and help them to make more informed decisions during the window replacement process.
Air Infiltration. Amount of air that passes between a window sash and frame. The lower the number, the less air the window lets pass through.
Argon. An inert, nontoxic gas which is six times denser than air, and is sandwiched between panes of glass to heat transfer.
Awning window. A window that is hinged at the top and swings out at the bottom, usually operated by a cranking mechanism.
Bay Window. A box-like assemblage of multiple windows, usually with one large central window surrounding by smaller windows on the sides, that projects out from the home.
Bow Window. A series of three to six tall windows assembled side by side in a gentle arc projecting from the side of a home.
Casement window. A window unit hinged at the side that swings outward, often operated by a cranking mechanism.
Condensation Resistance Factor. A measure of the effectiveness of a window or glazing system to reduce the potential for condensation. The higher the condensation resistance factor, the more energy efficient the window.
Divided lites. Division of window glazing using muntin bars.
Dormer window. Window that projects from a sloping roof.
Double hung window. Has two vertically moving sashes, each opening and closing a different part of the window. A single hung window has only one moving sash, usually the bottom half of the window.
Fixed lite. Window which does not open.
Frame. The stationary portion of a window installed into the opening in a wall, enclosing the sash.
French Door. Not really a door at all! A casement window that extends from the ceiling to the floor and features glass panes that run its entire height.
Gas-fill. An inert gas, usually argon or krypton, sealed between the panes of glass in a window instead of air. The gas is a better insulator than just air, and increases the thermal performance value of a window.
Header (also lintel or beam). Supporting member or beam above window opening which transfers building weight above to the supporting wall structure on each side of the window. “Header” usually refers to a wood beam. “Lintel” generally refers to a steel or masonry beam.
Header. The horizontal top of the frame.
Insulated glass. Two or more panes of glass separated by insulation at the edges and air (or inert insulating gas) in the middle to provide greater thermal efficiency in a window.
Insulating glass. Double- or triple-glazing with an enclosed and sealed gas space between the panes.
Jamb. A side jamb is the vertical molding of a window; the head jamb is the horizontal molding at the top. The bottom of the frame is referred to as a sill.
Krypton Gas. An inert, odorless, colorless, tasteless, nontoxic gas that is about 12 times denser than air. It is used to replace air between the glass panes to reduce heat transfer and deter convection.
Lite (also light). A window; or a pane of glass within a window.
Lintel. Horizontal member (wood, steel, or stone) over a window opening to support the weight of the wall above.
Low E (Emissivity) Glass. Glass with a transparent, usually multi layer, metallic oxide coating applied onto or into a glass surface. The coating reflects energy which improves the window’s insulating U-factor.
Mullion. Vertical member between window units. Not to be confused with muntins, which are secondary framing members that hold multiple panes of glass in the sash.
Muntin. A secondary framing member (horizontal, vertical, slanted) to hold the window panes in the sash. Often confused with “mullion.”
NFRC label. National Fenestration Rating Council, a non-profit organization sets energy certification and labeling standards for windows in the United States.
Rough Opening. The hole in the wall where a window or door unit will be installed.
Sash. The entire window, including the glass and the surrounding pieces that hold it together.
Sill. The horizontal bottom of the frame.
Sliding window. Windows which slides horizontally.
Solar Heat Gain Coefficient (SHGC). Ratio of the solar heat gained through a window to the solar radiant heat incident on the outside of the window.
U-factor. A measure of the rate of heat conduction through a surface of a window. The lower the U-factor, the better job a window does in keeping out heat and cold by conduction.
Visible Light Transmittance or VT. The fraction of light that is transmitted through glass. The higher the number the higher the fraction of visible light incident on the window that is transmitted.