Window & Door Terms

An odorless, colorless gas used to fill the space between panes in insulated glass units. Argon is denser than air and reduces heat transfer, improving the window's insulating ability by 30-40%.

A window hinged at the top that opens outward from the bottom. Provides ventilation even during light rain because the open sash acts as an awning.

A window that projects outward from the exterior wall, typically with a large center window flanked by two angled side windows. Creates a wider interior shelf and more natural light.

Similar to a bay window but with four or more windows arranged in a gentle curve rather than angled segments.

A type of exterior window trim (casing) originally designed for installation in brick openings. Now used generically for many window frame types.

A window hinged on one side that swings outward like a door using a crank mechanism. Provides excellent ventilation and an unobstructed view when open.

The trim material installed around the interior and exterior perimeter of a window or door frame. Covers the gap between the frame and the wall.

A protective layer applied to the exterior of a wood window frame — typically aluminum or vinyl. Provides weather protection while maintaining the wood interior appearance.

Water droplets forming on window surfaces. Exterior condensation (on the outside) is normal and indicates good insulation. Interior condensation (on the inside) indicates high humidity. Condensation between panes indicates seal failure.

A lock mechanism where a solid metal bolt extends into the door frame when locked. Provides significantly more security than a spring latch.

An insulated glass unit (IGU) with two panes of glass separated by a sealed air or gas-filled space. Standard for modern windows. Also called dual pane.

The most common window type. Both the upper and lower sashes slide vertically. Allows ventilation from the top, bottom, or both simultaneously.

A window that meets building code requirements for emergency escape — minimum 5.7 square feet of opening, 24 inches minimum height, 20 inches minimum width. Required in bedrooms.

An EPA certification for windows that meet energy efficiency standards for your climate zone. Energy Star windows in Colorado must meet Northern Climate Zone requirements.

The primary exterior door of a home. Available in fiberglass, steel, and wood. Modern entry doors include insulated cores, multi-point locks, and weatherstripping.

The arrangement and design of windows, doors, and other openings in a building. Affects energy efficiency, natural lighting, and architectural character.

An exterior door with a fiberglass skin over an insulated core. Resistant to denting, rotting, and warping. Can be stained or painted to mimic wood.

A window that doesn't open. Used for natural light, views, and architectural design in locations where ventilation isn't needed. Also called a picture window.

Thin metal (aluminum, copper, or galvanized steel) or membrane installed at joints, transitions, penetrations, and around windows and doors to prevent water entry. Critical around chimneys, skylights, walls, valleys, vents, and where siding meets other surfaces.

Low-expansion spray foam applied in the gap between the window frame and the rough opening. Provides insulation and air-sealing but must be applied carefully to avoid bowing the frame.

A window with visible condensation or haze between the panes, indicating the insulated glass seal has failed. The insulating gas has escaped, reducing energy efficiency.

The structural enclosure around the glass that holds the window in the wall opening. Made from vinyl, wood, fiberglass, aluminum, or composite materials.

A pair of doors with glass panels that open from the center. Can swing inward or outward. Used for patios, decks, and interior transitions.

Removing the entire existing window — frame, sash, and trim — down to the rough opening, then installing a completely new window unit. Required when the existing frame is damaged.

A window that projects outward with a glass roof, creating a small greenhouse-like shelf. Commonly installed over kitchen sinks.

The glass in a window. Single-glazed (one pane), double-glazed (two panes), or triple-glazed (three panes). Also refers to the process of installing glass.

Decorative bars that divide the glass into smaller panes. Can be between the glass (SDL), on the surface (applied), or true divided lites. Common patterns include colonial, prairie, and craftsman.

The mechanical components of a window or door — locks, handles, cranks, hinges, balancers, and rollers.

A window hinged at the bottom that opens inward from the top. Common in basements. The reverse of an awning window.

See Single-Hung and Double-Hung. Refers to windows with sashes that slide vertically.

Laminated glass designed to withstand impacts from wind-borne debris or hail. An inner plastic layer holds the glass together if broken. Relevant in Colorado's hail-prone areas.

The sealed glass assembly in a modern window — two or three panes with gas-filled spaces between them. The seal prevents gas loss and condensation between panes.

The vertical sides and horizontal top of the window or door frame.

A denser, more expensive alternative to argon for filling insulated glass units. Provides better insulation, especially in thinner gap widths. Used in premium windows.

The handle or bar at the bottom of the lower sash on a hung window, used to lift the sash open.

A pane of glass within a window. A 6-over-6 window has 6 lites in the upper sash and 6 in the lower sash.

Glass with a microscopically thin metallic oxide coating that reflects infrared heat while allowing visible light to pass through. Reduces heat transfer by 30-50%. Essential in Colorado's climate for both winter heat retention and summer heat rejection.

A structural element that divides two adjacent window units within a single frame. Different from a grille, which is decorative.

The dividing bar between glass panes in a true divided-lite window. Often confused with grille/grid.

The National Fenestration Rating Council's standardized ratings for window energy performance, including U-factor, SHGC, VT, and air leakage.

See Casement Window. Also refers to the crank mechanism that opens casement and awning windows.

A large door providing access to a patio or deck. Available as sliding, hinged (French), or folding (bi-fold) configurations.

A leading window and door manufacturer known for innovation, energy efficiency, and a wide range of styles. We are certified Pella installers.

See Fixed Window.

A premium window and door manufacturer known for custom options, excellent energy ratings, and durable construction. We are certified ProVia installers.

A measure of thermal resistance — how well a material resists heat flow. Higher R-value means better insulation. Standard siding has minimal R-value; insulated siding adds R-2 to R-5. For windows, R-value is the inverse of U-factor (e.g., U-factor 0.25 = R-value 4.0).

A window designed to fit into an existing window opening without modifying the surrounding wall. Also called insert or pocket replacement.

The framed opening in the wall structure where a window or door is installed. Slightly larger than the unit to allow for shimming and insulation.

The movable or fixed framework within the window frame that holds the glass. In a double-hung window, there's an upper sash and a lower sash.

The fraction of solar radiation that passes through a window, measured from 0 to 1. Lower SHGC blocks more heat. In Colorado, moderate SHGC (0.25-0.40) balances winter solar heating with summer cooling.

A narrow, fixed or operable window panel flanking an entry door. Sidelites add natural light and visual width to the entryway.

The horizontal bottom piece of a window or door frame. Interior sills provide a shelf; exterior sills slope outward to shed water.

A window where only the lower sash slides up. The upper sash is fixed. Less expensive than double-hung but offers less ventilation flexibility.

A window with sashes that slide horizontally along tracks. Common for wide openings and where vertical clearance is limited.

The component between glass panes in an IGU that maintains the gap width and houses desiccant to absorb moisture. Warm-edge spacers reduce heat loss at the glass edge.

An exterior door with a steel skin over an insulated core. The most secure and affordable option. Resists forced entry but can dent and rust if the finish is compromised.

Glass that has been heat-treated to be 4x stronger than regular glass. When broken, it shatters into small, relatively harmless pieces. Required by building code near doors, in bathrooms, and close to floor level.

The bottom of an exterior door frame. Creates a seal between the door and the floor/sill. Adjustable thresholds compensate for settling and seal wear.

A feature on modern hung windows that allows the sash to tilt inward for easy cleaning from inside the house. Eliminates the need for ladder access.

A window above a door or another window. Can be fixed or operable. Adds height, light, and architectural interest.

An insulated glass unit with three panes of glass and two gas-filled spaces. Provides superior insulation but adds cost and weight. Most beneficial in extreme climates.

A measure of how much heat passes through a window. Lower U-factor means better insulation. Energy Star requires U-factor of 0.30 or lower in Colorado's Northern Climate Zone. The inverse of R-value.

Window frames made from PVC (polyvinyl chloride). Low-maintenance, energy-efficient, and affordable. The most popular frame material for replacement windows.

The fraction of visible light that passes through a window, measured from 0 to 1. Higher VT means more natural light. Typical range is 0.30-0.70.

Flexible material installed around the edges of doors and operable window sashes to seal the gap when closed. Prevents air and water infiltration. Deteriorates over time and should be replaced.