Windows Glossary of Terms

Air Chambers

Small honeycomb spaces within the sash and frame which help
to insulate and strengthen the window

Air Infiltration

The amount of air that passes between a window sash and frame.
In windows it is measured in terms of cubic feet or air per
minute, per square foot of area. The lower the number, the
less air the window lets pass through.

Air Latch

Latch mechanism on the interior face of the sash that retains
the window in a partially open position for ventilation.

Angled Exterior

A sloped extension from the frame that adds an aesthetically-pleasing
dimension to the exterior of the window.

Argon gas

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.

Astragal

The center member of a double door, which is attached to the fixed or
inactive door panel.

Awning window

A window unit in which the bottom of the sash swings outward for
ventilation.

Balance System

Device
for holding vertically sliding sash in any desired position
through the use of a spring or weight to counterbalance the
weight of the sash.

Bay window

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.

Beveled
Exterior

An
angled extension from the frame that adds an aesthetically-pleasing
dimension to the exterior of the window.

Block frame window

Used when replacing the wood sash of an old double hung wood window.

Bow window

A composite of four or more window units in a radial or bow formation.

Breather Tubes

A small metal tube that is placed into an insulated unit’s spacer to
equalize pressure differences. Breather tubes can allow moisture to enter
into the insulating unit. Mostly used in high altitude locations.

Brickmold

A type of external casing which frames windows and doors.

Butyl

A rubber material that seals the glass to the spacer, creating
an airtight and watertight IG unit. Butyl has the lowest
gas permeability of all rubbers.

Cam Lock and Keeper

The
mechanisms which pull the sash together when placed in the
locked position.

Capillary Tubes

Small hollow tubes which penetrate the spacer system of an insulating
glass unit. They allow pressure equalization between manufacturing
locations, shipping, and installation locations. Since the
insulating glass unit is not permanently sealed, the air space
cannot be filled with Argon gas.

Casement window

A window unit in which the single sash cranks outward, to the right or
left.

Casing

Molding of various widths, thickness and shapes applied to the framework
of window and door units.

Center of Glass U- and R-values

The U- and R-values measured from the center of the glass to 2-1/2″
from the frame.

Check rail

On a double-hung window, the bottom rail of the upper sash and the upper
rail of the lower sash, where the lock is mounted.

Circlehead

A generic term referring to any of a variety of window units with one or more curved frame members, often used over another window or door opening.

Cladding

Any material locked to the outside faces of doors and windows to provide a
durable, low-maintenance exterior surface.

Clerestory window

A venting or fixed window above other windows or doors on an upper outside
wall of a room.

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 efficient the window
and glazing system.

Conduction

Energy
transfer from one material to another by direct contact.

Convection

Heat
transfer by currents that flow from a warm surface to a colder
one.

Cottage double-hung

A double-hung window in which the upper sash is shorter than the lower
sash.

Coved Exterior

An arced extension from the frame that adds an aesthetically-pleasing
dimension to the exterior of the window.

Dormer

A space which protrudes from the roof of a house, usually including one or
more windows.

Double-hung window

A window unit that has two operable sashes which move vertically in the frame.

Drip cap

A molding placed on the top of the head brickmold or casing of a window
frame.

Double or dual glazing

Use of two panes of glass in a window to increase energy efficiency and provide other performance benefits.

Extrusion

A form produced by forcing material through a die. Most window frames are
clad with extruded vinyl or aluminum.

Fenestration

An architectural term referring to the arrangement of windows in a wall. From the Latin word, “fenestra,” meaning window.

Fixed window

Non-venting or non-operable window. Also known as picture window.

Flashing

A thin strip of metal or synthetic material that diverts water away from a
window or skylight.

Flush Fin

A replacement window with flush fin is used when replacing an existing
aluminum sliding window. This is the most commonly used replacement window type.

Foam Spacer

Foam material placed in the airspace of the insulating glass in a window
to enhance the appearance and improve the performance of the window.

Frame

The enclosure in which window sash or door panels are mounted.

French hinged door

Hinged door(s) which have wider panel members around the glass.

French sliding door

A sliding door which has wider panel members around the glass, giving the appearance of a French hinged door.

Glazing

Glass in a window or door; the act or process of fitting with glass.

Glazing bead

A plastic or wood strip applied to the window sash around the perimeter of the glass.

Glazing stop

The part of the sash or door panel which holds the glass in place.

Grille

A term referring to windowpane dividers or muntins, usually a type of
assembly which may be detached for cleaning.

Head

The main horizontal member forming the top of the window or door frame.

Header

A horizontal framing member placed over the rough opening of a window to
prevent the weight of wall or roof from resting on the window frame.

Hopper

A window unit in which the top of the sash swings inward.

Insulating glass (IG)

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.

Jalousie window

Louver blades open to maximize airflow through opening.

Jamb

The main vertical members forming the sides of a window or door frame.

Jamb liner

In a modern double-hung window, the track installed inside the jambs on
which the window sashes slide.

Knocked down (KD)

Unassembled window or door unit.

Lift

A handle or grip installed on the bottom rail of the lower sash of a double-hung window to make it easier to raise or lower the sash.

Light or lite

Glazing framed by muntins and/or sash in a window or door.

Light shaft

An insulated shaft built to direct the light from a roof window or skylight through the attic to the room below.

Low-E glass

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.

Masonry opening

The space in a masonry wall left open for windows or door.

Mortise

A slot or rectangular cavity cut into a piece of wood to receive another
part.

Mortise-and-tenon

A strong wood joint made by fitting together a mortise in one board and a matching projecting member (tenon)
in the other.

Mullion

A wood or metal part used to structurally join two window or door units.

Muntin

Applies to any short or light bar, either vertical or horizontal, used to
separate glass in a sash into multiple lights. Also called a windowpane
divider or a grille.

Muntin Bar

Any small bar that divides a windows glass. Also called a grille or
windowpane divider.

Nail-on

Windows with nail-on frames are for new construction.

Palladian window

A large, arch-top window flanked by smaller windows on each side.

Panel

Usually refers to the separate panel or panels in a door frame.

Parting stop

In a double-hung window, a strip of wood applied to the jamb to separate
the sash.

Passive solar collector

Any glazed area in the walls or roof of a building pointed to the south to take maximum advantage of the sun’s heat without a mechanical (or active) method of storage or distribution of the heat.

Picture

Non-venting or non-operable window. Also know as a fixed window.

Rail

The top and bottom horizontal members of the framework of a window sash.

Rough opening

The framed opening in a wall into which a window or door unit is to be
installed.

R-Value

Resistance to thermal transfer or heat flow. Higher R-value numbers
indicate greater insulating value.

Pane

A framed sheet of glass within a window.

Sash

A single assembly of stiles and rails made into a frame for holding glass.

Sash balance

A system of weights, cords and/or coiled springs which assist in raising double-hung sash and tend to keep the sash in any placed position by counterbalancing the weight of the sash.

Sash cord

In double-hung windows, the rope or chain which attaches the sash to the
counter balance.

Sash lift

A protruding handle screwed to the inside bottom rail of the lower sash on
a double-hung window.

Sash weights

In older double-hung windows, the concealed cast-iron weights which are
used to counterbalance the sash.

Seat board

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.

Shims

Wood wedges (often wood shingles) used to secure the window or door unit in the rough or masonry opening in a square, level and plumb position during and after installation.

Sidelights

Narrow fixed units mulled or joined to door units to give a more open
appearance.

Sill

The main horizontal member forming the bottom of the frame of a window or
door.

Simulated divided light

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.

Single glazing

Use of single panes of glass in a window. Not as energy-efficient as
double glazing.

Single-hung

A double-hung type of window in which the top sash is fixed or inoperable.
Sloped Sill Adapter

Used to cover the gap between the old sloped sill window and the new block frame window. It adapts a new window to the existing sloping sill.

Solar gain

The process of providing a net heat gain within a structure, over and above the normal heat loss, by passive collection of the sun’s heat through windows and other glazed areas.

Stile

The main vertical members of the framework of a sash.

Stool

An interior trim piece on a window which extends the sill and acts as a
narrow shelf.

Stop

A molding used to hold, position or separate window parts.

Tempered glass

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.

Tenon

A rectangular projection cut out of a piece of wood for insertion into a
mortise.

Thermal break

The addition of a thermal insulating material between two thermally
conductive materials.

Transom

A small window that fits over the top of a door or window, primarily for
additional light and aesthetic value.

True divided light

A term which refers to windows in which multiple individual panes of glass or lights are assembled in the sash using
muntins.

U-value

Rate of heat flow-value through the complete heat barrier, from room air
to outside air. The lower the U-value, the better the insulating value.

Unison lock

A casement locking system which secures the window at two locking points by operation of one handle.

Vapor barrier

A watertight material used to prevent the passage of moisture into or through floors, walls and ceilings.

Vent Unit

A window or door unit that opens or operates.

Vinyl

A plastic material used for cladding or entire window units.

Weatherstripping

A material or device used to seal the openings, gaps or cracks of venting
window and door units to prevent water and air infiltration.

Windload

Force exerted on a surface by moving air.

One Response to Windows Glossary of Terms

  1. Grizzly says:

    Tip top stuff. I’ll execpt more now.

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