A Replacement Windows Glossary of Terms
Ensuring proper replacement window installation can be quite a challenge. What questions should you ask? What terms should be 'under your belt'? To help you get started, we have put together a glossary of important terms. Take time to familiarize yourself with the basics. When you are ready to proceed you'll feel much more comfortable speaking with your contractor.
A
Shaped like a honeycomb, air chambers are small spaces located within the sash and frame that help insulate and strengthen a window.
Air infiltration is the amount of air measured by cubic feet per minute that can pass through a window frame.
The air latch is a handle on the sash's interior that holds a window open.
Airspace is equal to ½" to ¾" between the panes of glass in a window.
An angled exterior is a sloped extension from the window frame.
An odorless, colorless gas that is denser than air, argon gas is used between the windowpanes to reduce heat loss.
An awning window has a top hinge that swings outward from the bottom for proper ventilation.
B
A balance system uses springs or weights to hold a vertical sash in any desired position.
Three windows joined at 30- or 45-degree angles make up a bay window that protrudes from the exterior wall of a house.
A beveled exterior is an angled extension from the frame on the exterior of a house.
A bow window is similar to a bay window with the difference being in the number of windows. Bow windows are an angled combination of windows in 3-, 4- or 5-lite configurations. The windows are attached at 10-degree angles creating a semi-circular look.
The brick mold is the exterior casing around a door or window that cover the jambs.
A hot rubber sealant, butyl, seals the glass to the spacer so no air or water can get in.
C
The cam lock and keeper mechanisms keep the window sashes together when locked.
Capillary tubes are small hollow tubes that penetrate the spaces of glass and allow pressure to be equalized at all times.
A casement window has an outward side opening with hinges at the top and bottom of the frame.
The center of glass U- and R-values are measured from the center of the glass to 2-1/2" from the frame.
The condensation resistance factor measures the effectiveness of a window to reduce condensation. A higher number means better efficiency.
Energy transfers by means of conduction between two materials with direct contact.
Heat transfers via convection by the circulation of currents from a warm surface to a colder one.
A coved exterior is an arced extension of a window on the outside of a house.
D
The space between the two panes of a double- or triple-pane window is called dead-air space.
A deadlite is a piece of glass with a sash around it, but isn't set in the main frame of a window.
With its high water absorbency, desiccant is a material used in glass to absorb water vapor, which causes fogging.
A double-hung window has two operable sashes that open up and down.
Double-strength glass has a thickness of approximately 1/8".
An alternative method of placing glass in a door or window is called dry glazing.
Dual durometer is a vinyl bead material with two different degrees of hardness. The softer part is up against the window and the harder part is inserted into the sash.
E
The Egress Code, a law requiring a minimum opening of a window for persons to exit or firefighters to enter.
Energy Star is a U.S. government program that establishes a standard set of guidelines used with a variety of building materials to measure energy efficiency. These products meet strict governmental guidelines.
Different from a roll-formed frame, an extruded screen frame is pressed through a form or die.
F
The process of joining two materials into one by melting them together under temperatures more than 500ºF, is called fusion-welded.
G
Geometric windows are specially designed to create rectangles, triangles, half-rounds, full-rounds, ellipses and more.
Glass is a transparent material made up of sand, soda, and lime.
A glazing bead is a strip of vinyl placed around the edge of a piece of glass. This holds it in place along with other sealants.
Grids create the look of several smaller panes of glass within a large one.
A grille is a window pane divider that usually can be removed for cleaning.
H
The head is at the top of a window and is the horizontal portion of the main window frame.
A head expander is usually a u-shaped piece of vinyl placed on the head of a window to be used as filler. This piece will expand or lengthen a unit and fill a gap.
Hermetically sealed windows are completely sealed against the escape or entry of air.
A hook accessory connects to the hook frame for easy installation.
A window with a bottom hinge that opens inward for ventilation is known as a hopper.
I
An I.G. Unit, or insulating glass unit, is a window with two or three panes and an insulating air space between them. I.G. units increase energy performance of a window.
Insulating glass is two or more pieces of glass enclosing a hermetically sealed airspace to reduce thermal loss.
J
A j-channel is used around the exterior of a window where the siding fits. It extends beyond the window to the outside edges of an adjoining j-channel.
The vertical parts of the frame on both sides of the window are the jambs.
K
On the sash, the keeper rail is the vertical part where the keeper is attached.
On the sash, the keeper stile is the horizontal part where the keep is attached.
On a door, a kickplate is a metal plate attached to one or two sides of a door's bottom to prevent denting and soiling of the door.
Krypton gas is an odorless and colorless gas that replaces air between two or more glass panes. Krypton is denser than air and works better to deter heat transfers
L
Glass that is bonded together by two or more pieces of plastic using heat and pressure is laminated glass. This process protects ultraviolet rays.
Open or close a window with its lift handle.
Open or close a window with a lift rail, which unlike a handle, goes across the entire sash.
A lite is a single unit of glass in a window.
The horizontal part of a sash where the cam lock is attached is the lock rail.
The lock stile is a vertical section of a sash where the cam lock is attached.
Low E glass is coated with a transparent metallic product to allow short-wave energy to pass through but blocks the passage of infrared energy.
M
The main frame includes the head, sill, and jambs of a window.
A mechanically fastened frame is fastened with screws instead of other methods.
The meeting rail is the horizontal part of a pair of sashes that meet when the sashes are closed.
The meeting stile is the vertical part of a pair of sashes that meet when they are closed.
Mesh is a fabric made of fiberglass or aluminum used for screens on windows and doors.
When two windows are joined together side by side, they are mulled.
A mullion is a vertical or horizontal connecting unit dividing windows or doors.
A muntin bar is a strip of wood or metal used to divide and hold panes of glass in a window. Also known as a grille or mullion.
N
When a window is National Certified Testing Labs (NCTL)-validated, it meets certain standards and is at a proper quality control level.
When a window, door, or skylight has an NFRC rating it means that an energy rating was appropriated by National Fenestration Rating Council (NFRC), a non-profit group of manufacturers, builders, designers, government officials, utilities, and consumers providing unbiased energy performance ratings.
A nailing fin, or brick mold, is a strip of metal secured to the main frame of a window and used to strengthen and secure a unit to an opening.
O
Obscure glass is translucent instead of transparent. It is typically used for bathroom windows.
With a 60/40 configuration, an oriel is a window with the meeting rail located off center of the frame.
P
A patio door is made up of two panes of glass, slides open and closed but has only one operable sash.
A picture window is a large window usually on the front of a house and has no moveable sash.
Plumb means that a unit is vertically level.
R
The R-value is equal to the resistance a material has to heat flow. The higher the R-value, the greater the resistance.
Radiation is wave energy transmitted from one object to another through the atmosphere or through transparent or translucent materials.
The rail is the horizontal part of the sash.
S
The moveable part of the window that holds a pane of glass is the sash.
The horizontal, bottom part of the frame is the sill.
A window in which one sash slides up and down and the other sash doesn't move is considered single hung.
Single-strength glass has a thickness of approximately 3/32".
A slider window has a sash that moves back and forth as opposed to up and down.
A sloped sill is the exterior bottom part of a window that has a downward slope to allow for water runoff.
The solar heat gain coefficient measures the percentage of heat entered through glass from both direct sunlight and absorbed heat. The smaller the number, the greater the reductions of heat gain.
The vertical parts of a sash are the stiles.
T
Tempered glass breaks into pebbles rather than shards when it is broken.
A tilt latch unlocks the sash and allows it to tilt in from the main frame.
A transom is a horizontal crosspiece over a door or between a window and a door. It refers to a small, hinged window above a door or another window.
U
U-value refers to how much heat passes through the glass. The lower the U-value, the better the insulating quality.
UV block measures the percentage of ultraviolet rays blocked from being transmitted through the glass. The higher the number, the lower the percentage of rays transmitted through the window.
V
Also called the sash, the vent is the vertically sliding part of a window.
A vent lock allows a window to remain locked partially open for ventilation.
The visible light transmittance is a percentage of light that is transmitted through glass. The higher the number the higher the percentage of light transmitted through the window.
W
The material used to form a weather-resistant seal around an operable sash is the weather-stripping.
Weep flaps are holes covered with vinyl to let water escape and keep bugs out.
Small openings on the exterior sill are weep holes. They are designed to allow water to escape that might otherwise accumulate in a window's sill.
Slots or holes in the sill (bottom) that allow water to run outside are weep slots.
Wet glazing uses a silicone-based substance to secure and seal glass to a sash.
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