Window & Door Terms, Explained

The amount of outside air that leaks into a home through and around a window or door, usually measured under standardized test conditions.

A performance value that indicates how much air passes through a window or door assembly; lower numbers mean tighter, more efficient units.

A window with frames made primarily from aluminum, known for strength and slim profiles but typically less efficient without thermal breaks.

Standard untreated float glass that has been slowly cooled to relieve internal stresses; more likely to break into large shards than safety glass.

An inert gas commonly used between panes of insulated glass to reduce heat transfer and improve energy efficiency.

A window hinged at the top that opens outward from the bottom, allowing ventilation even during light rain.

A window configuration that projects outward from an exterior wall, typically made of a fixed center unit flanked by angled side windows.

The lower horizontal part of a window sash or frame, providing structure and support for the glass.

A multi-panel window that curves outward from a wall, usually made of four or more equal-sized units to create a gentle arc.

Exterior trim that surrounds a window or door frame, creating a finished transition between the unit and the siding or brick.

A secondary frame installed inside a rough opening to provide a stable, square surface for mounting new windows or doors.

The collective exterior components of a home—walls, roof, windows, and doors—that separate indoor conditioned space from the outdoors.

A locking device on a sash window that pulls the sashes together for security and tighter weathersealing when engaged.

A metal or flexible flashing installed over trim or siding to direct water away from window and door openings.

A side-hinged window that swings outward like a door, operated with a crank handle for secure, tight-sealing ventilation.

Interior or exterior trim that covers the gap between the window or door frame and the wall surface for a finished look.

Sealant used to fill gaps and joints around windows and doors to reduce air leakage and water penetration.

An exterior covering, often aluminum or fiberglass, applied to wood window or door frames for added weather resistance and low maintenance.

A window made from a blend of materials—such as wood fibers and polymers—to balance strength, stability, and maintenance needs.

Moisture that forms on glass or frames when warm, humid indoor air contacts a cooler surface and reaches its dew point.

A faint mark or stain that may appear where condensation has repeatedly formed and dried along the bottom of glass or frames.

A performance measure of how well a window or door resists forming condensation on interior surfaces under normal conditions.

A window built to specific dimensions to fit a particular opening rather than using a standard stock size.

The visible glass area of a window through which natural light passes, smaller than the overall frame size.

Moisture-absorbing material placed inside insulated glass spacers to help keep the air space between panes dry and clear.

The load a window or door is rated to withstand from wind and other forces without failing under test conditions.

A fixed window where the glass is installed directly into the frame without an operable sash, maximizing glass area.

Two panes of glass separated by an air or gas-filled space to improve insulation and comfort compared to single-pane glass.

A window with two vertically sliding sashes, allowing the top, bottom, or both to open for ventilation.

A piece of flashing or trim installed above windows and doors to help shed water away from the unit.

An interior finish detail where drywall wraps directly to the window frame instead of using traditional casing trim.

A window sized and installed to meet building code requirements for emergency escape and rescue, typically in bedrooms and basements.

A general term for performance labels that summarize how well a window or door helps manage heating and cooling loads.

A window that meets federal energy performance criteria for a given climate zone as part of the Energy Star program.

A designed gap or flexible joint that allows building materials, including window systems, to expand and contract without damage.

The trim on the outside of a window or door that covers the framing gap and adds architectural style.

The visible finish material around the outside of a window or door that covers gaps and adds architectural detail.

A window that arrives from the manufacturer with its color or stain already applied under controlled conditions.

A building term referring collectively to windows, doors, skylights, and other glazed openings in the building envelope.

A window with frames made from fiberglass, valued for strength, low expansion, and durability in extreme temperatures.

A non-operable window designed only for light and views, with no moving sash or ventilation function.

A thin extension around a window or new-construction unit that fastens to the wall sheathing to anchor and seal the frame.

Water-resistant material installed around windows and doors to help direct water away from the opening and prevent leaks.

The outer structure of a window or door that surrounds and supports the sash or panel and anchors the unit to the wall.

The primary substance used to build a window or door frame, such as wood, vinyl, fiberglass, aluminum, or composites.

A door with a large glass panel occupying most of the slab, allowing generous light and views.

A window replacement method where the entire existing frame and trim are removed down to the rough opening before installing a new unit.

Another term for full-frame replacement, where the entire existing window, frame, and trim are removed before installing the new unit.

The glass portion of a window or door, including single, double, or triple panes and any coatings applied to the glass surfaces.

The interior or exterior strip that helps secure glass within a window sash or frame.

The recess within a sash or frame where the glass sits and is held in place by glazing beads or stops.

Trim or profiling that holds the glass securely within a sash or frame, often removable for glass replacement.

Decorative or functional bars that divide a window’s glass into smaller sections, often for a traditional appearance.

A door with a glass panel in the upper portion and a solid lower section for privacy and style.

Flashing installed above the head of a window or door to help prevent water from entering at the top of the opening.

The top horizontal part of a window or door frame.

The amount of solar or outdoor heat that enters a home through windows and doors, impacting cooling loads.

A window hinged at the bottom that opens inward from the top, often used in basements or small spaces.

A window tested and approved to withstand specific impact and pressure standards, often required in coastal or storm-prone regions.

A specially engineered glass and frame system designed to withstand wind-borne debris and severe weather impacts.

A hinged door that opens toward the interior of the home, common on many entry and patio doors.

The overall feeling of temperature, humidity, and air movement inside a home as influenced by windows, doors, and insulation.

A type of window replacement where the new unit is installed inside the existing frame, leaving interior and exterior trim largely intact.

The promise made by the contractor or installer covering workmanship and labor-related issues after the window is installed.

A factory-sealed assembly of two or more glass panes separated by a spacer and air or gas-filled space for improved insulation.

The decorative trim on the inside of a window or door that covers the gap between the frame and wall.

The trim or profiling inside a window frame that helps hold the sash or glass in place.

The vertical or horizontal framing members that form the sides and top of a window or door frame.

Material added to the inside edge of a window or door frame to match the wall thickness and meet interior trim or drywall.

A narrow groove cut into a frame or stop, often used to accept weatherstripping around a window or door.

Glass made by bonding two or more layers with a plastic interlayer, improving safety, security, and sound reduction.

The horizontal part of a sash used as a handhold to raise or lower the operable portion of a window.

An individual glass pane within a window or a section defined by muntins or grids.

Glass with a microscopically thin coating that reflects portions of infrared and UV energy while allowing visible light to pass through.

An outside surface designed to resist weathering and reduce the need for repainting, scraping, or refinishing.

A surface treatment or material, such as vinyl or cladding, that requires little ongoing painting or refinishing.

The coverage offered by the window producer on materials and factory workmanship for a defined period of time.

A vertical or horizontal structural member that joins two or more window or door units together in a single opening.

A grille or bar that divides a window’s glass area into multiple lites for visual style, often without separating the glass itself.

See Flange; the exterior mounting surface used to secure new-construction windows to the wall sheathing.

A window designed with a nailing fin or flange to be installed directly into the wall framing of new or heavily remodeled structures.

Glass that has been textured or treated to limit visibility while still transmitting light, often used in bathrooms or entry doors.

The part of a window that holds the glass and moves to open or close for ventilation.

A window that can be opened and closed for ventilation, such as casement, awning, or double-hung units.

A hinged door that opens toward the exterior of the home rather than swinging inward.

The ability of a window or door system to reduce traffic, neighborhood, or environmental sound entering the home.

A single sheet of glass within a window or door assembly.

A large glass door, often sliding or hinged, that provides access to a patio, deck, or backyard while letting in light.

A standardized rating that indicates how well a window or door performs under specific structural, air, and water test pressures.

A large fixed window designed primarily for views and daylight, without any operable sash.

A window that rotates on a central pivot point, allowing the sash to swing inward or outward around a fixed axis.

Any glass designed to limit direct visibility into a space, typically through texture, tint, or patterns.

A measure of how well a material resists heat flow; higher R-values indicate better insulating performance.

A window designed to fit into an existing frame or opening with minimal disturbance to surrounding finishes.

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

The framing member at the bottom of a rough opening where a window or door will sit, usually supported by cripples.

The part of a window that holds the glass and may move or be fixed within the frame.

Devices installed to restrict how far a window sash can open, often for safety or security reasons.

The main locking mechanism that secures an operable sash in the closed position.

A secondary locking device that allows a window to be partially open while still providing some resistance to forced entry.

The structural panel, such as OSB or plywood, attached to exterior wall framing to support siding and help brace the structure.

The small gap left between a window or door frame and the rough opening to allow for leveling and adjustment with shims.

Thin wedges used to adjust and support a window or door frame within a rough opening so it sits plumb, level, and square.

A narrow, vertical window placed alongside a door to add light and visibility.

The visible edge profile of the glass and frame when viewed straight on, affecting how open or framed a window appears.

The visible portion of the frame when looking through a window opening, influencing how much glass area is perceived.

The bottom horizontal part of a window frame that supports the sash and helps shed water toward the exterior.

A sloped, waterproof support at the base of a rough opening that helps direct any water out and away from the wall.

Grids or muntins applied to the surface of the glass to create the look of multiple panes while using a single insulated glass unit.

A window with two sashes where only the bottom sash moves and the top sash remains fixed.

A window with only one layer of glass, offering minimal insulation compared to double- or triple-pane units.

A rating that measures how much solar heat passes through a window; lower SHGC values reduce heat gain from the sun.

A rating that indicates how well a window or door reduces airborne sound; higher numbers mean better sound control.

The component that separates panes of glass in an insulated glass unit and helps maintain the air or gas space between them.

The finished size of the framed space in a wall that must safely support and surround a window or door unit.

Heat-treated safety glass that is stronger than regular glass and breaks into small, less sharp pieces when shattered.

An insulating barrier within a metal window or door frame that reduces the transfer of heat and cold.

The tendency of materials to expand or contract when temperatures change, which can affect how windows and doors operate.

The overall measure of how well a window or door system resists heat transfer and supports indoor comfort.

Aluminum framing that includes an insulating section to reduce heat transfer and improve comfort compared to solid aluminum frames.

A sash on a double- or single-hung window that can tilt inward from the top for easier cleaning of the exterior glass from inside.

A European-style window that can tilt inward at the top for ventilation or swing inward from the side for full opening.

A smaller window installed above a door or larger window to bring in extra light or provide ventilation.

Three panes of glass with two air or gas spaces between them to improve insulation and comfort over double glazing.

A traditional window design where individual lites of glass are separated by actual muntin bars within the sash.

A performance rating that measures how easily heat flows through a window or door; lower U-factors mean better insulation.

The gradual discoloration or damage to fabrics, flooring, and furnishings caused by ultraviolet light passing through windows.

To allow fresh air to move into and through a space, often by opening windows or doors.

A window with frames made from PVC (polyvinyl chloride), valued for low maintenance and good energy performance when properly built.

A rating that indicates how much visible light passes through a window; higher VT values let in more daylight.

An insulated spacer design used in insulated glass units to reduce heat loss and edge-of-glass condensation compared to metal spacers.

Water that leaks into a home around or through a window or door assembly, often due to poor sealing or flashing.

Flexible material installed around sashes and frames to help reduce air and water leakage when windows or doors are closed.

Small openings at the bottom of some window and door frames that allow trapped water to drain to the exterior.

The front-to-back thickness of a window frame, which must match or be adapted to the wall construction for proper installation.

The process of removing old windows and installing new units to improve comfort, efficiency, or appearance.

The slight downward angle of an exterior sill or surface to help shed water away from the window.

Trim or a profile that limits the movement of a sash or holds it in position within the frame.

The written guarantee provided by a manufacturer or installer that outlines what is covered if a window has defects or performance issues.

A window with a wood interior frame and an exterior surface covered in another material, such as aluminum or fiberglass, for protection.