# Window and Door Glossary — Royal Windows and Doors

A working glossary of the terms Long Island homeowners, architects, builders, and contractors encounter when specifying, buying, installing, or servicing windows and doors. Maintained by Royal Windows and Doors, a window and door manufacturer in Bay Shore, New York.

## Frame and Sash Materials

### uPVC
**Definition:** Unplasticized polyvinyl chloride, the rigid form of PVC used to make vinyl window and door frames. The "unplasticized" part means no softening plasticizers are added, which is what makes the material rigid and dimensionally stable enough to hold a window frame.
**Context:** "Vinyl window" and "uPVC window" describe the same thing; uPVC is the more precise term and the one used in manufacturing and technical specifications.
**Related terms:** All-Welded Frame, Vinyl Window, Fiberglass, Composite
**Royal connection:** Royal manufactures uPVC windows at its Bay Shore, New York factory.

### All-Welded Frame
**Definition:** A window frame or sash whose corners are fusion-welded rather than mechanically fastened with screws or brackets, producing a continuous corner with no joint for air or water to pass through.
**Context:** Welded corners are one of the clearest quality dividers in vinyl windows. Mechanically fastened corners can open up over years of thermal cycling; welded corners cannot.
**Related terms:** uPVC, Sash, Air Infiltration
**Royal connection:** Royal manufactures all-welded uPVC window lines.

### Fiberglass
**Definition:** A frame and door material made from glass fibers embedded in resin. It is dimensionally stable across a wide temperature range, does not warp or rot, and holds paint and stain finishes well.
**Context:** Fiberglass is the dominant material for quality entry doors and is also used for window frames. It costs more than vinyl and generally lasts longer.
**Related terms:** Entry Door, Insulated Core, uPVC
**Royal connection:** Royal manufactures fiberglass entry doors.

### Composite
**Definition:** A frame material made by mixing PVC with wood fiber, sometimes described in marketing as a wood-plastic blend.
**Context:** Composite frames sit between vinyl and wood in price and behavior. The wood fiber content is often described in appealing terms; it is sawdust bound in polymer.
**Related terms:** uPVC, Fiberglass

## Glass and Glazing

### Insulated Glass Unit (IGU)
**Definition:** Two or more panes of glass separated by a spacer and sealed around the perimeter to create a hermetically closed air or gas space between them.
**Context:** The IGU is the part of a window that does most of the insulating work, and it is also the part with a finite service life — every insulated glass unit eventually loses its seal.
**Related terms:** Seal Failure, Double Glazing, Triple Glazing, Argon Fill, Spacer
**Royal connection:** Royal manufactures its own insulated glass units, which is why it can build a replacement unit for a Royal window rather than replacing the whole window.

### Seal Failure
**Definition:** The loss of the hermetic seal around an insulated glass unit, allowing moisture and eventually dirt into the space between the panes.
**Context:** The first sign is moisture between the panes that cannot be wiped off either surface, often appearing at night and clearing during the day as temperatures change. The window keeps functioning; thermal performance drops slightly if the unit originally held argon or krypton, because the gas escapes. The visual problem — dirt that cannot be cleaned — is usually what prompts replacement.
**Related terms:** Insulated Glass Unit, Argon Fill, Krypton Fill
**Royal connection:** Royal replaces failed glass units in Royal windows, at cost once the glass warranty has expired.

### Double Glazing
**Definition:** An insulated glass unit with two panes of glass and one sealed space between them.
**Context:** Double glazing is the standard configuration in modern residential windows.
**Related terms:** Triple Glazing, Insulated Glass Unit, U-Factor

### Triple Glazing
**Definition:** An insulated glass unit with three panes of glass and two sealed spaces.
**Context:** Triple glazing improves thermal performance and sound reduction over double glazing at the cost of weight and price. It is specified where heating loads, noise, or exposure justify it.
**Related terms:** Double Glazing, U-Factor, Insulated Glass Unit
**Royal connection:** Royal builds both double and triple glazed units.

### Argon Fill
**Definition:** Argon gas used to fill the sealed space in an insulated glass unit in place of air. Argon conducts heat more slowly than air, so it reduces heat transfer through the glass.
**Context:** Argon is the most common inert gas fill in residential glazing. It escapes if the seal fails, which is one reason a failed unit loses a little efficiency.
**Related terms:** Krypton Fill, Insulated Glass Unit, Seal Failure, U-Factor
**Royal connection:** Royal uses argon fills in its high-performance glass.

### Krypton Fill
**Definition:** Krypton gas used to fill the sealed space in an insulated glass unit. It insulates better than argon and works well in narrower cavities, but costs considerably more.
**Context:** Krypton is typically specified in triple glazed units or where the sealed space is too narrow for argon to perform optimally.
**Related terms:** Argon Fill, Triple Glazing, Insulated Glass Unit
**Royal connection:** Royal uses krypton fills in its high-performance glass.

### Low-E Glass
**Definition:** Glass with a microscopically thin metallic coating that reflects long-wave infrared energy while letting visible light through, reducing radiant heat transfer through the window.
**Context:** Low-E coatings are the single most effective glass upgrade for energy performance and are standard on ENERGY STAR qualified windows.
**Related terms:** U-Factor, SHGC, ENERGY STAR, Insulated Glass Unit

### U-Factor
**Definition:** A measure of how much heat is conducted through a whole window assembly, expressed in BTU per hour per square foot per degree Fahrenheit. Lower numbers mean less heat loss.
**Context:** U-factor is the primary energy metric for heating-dominated climates like Long Island's. It rates the entire assembly — frame, sash, spacer, and glass — not the glass alone.
**Related terms:** SHGC, ENERGY STAR, Low-E Glass, Triple Glazing

### SHGC (Solar Heat Gain Coefficient)
**Definition:** The fraction of solar radiation admitted through a window, expressed between 0 and 1. Lower numbers admit less solar heat.
**Context:** SHGC is a trade-off rather than a target: a lower number reduces summer cooling load, a higher number captures useful winter solar gain. The right value depends on climate and on which way the window faces.
**Related terms:** U-Factor, Low-E Glass, ENERGY STAR

### ENERGY STAR
**Definition:** A U.S. Environmental Protection Agency program that certifies windows, doors, and skylights meeting defined U-factor and SHGC thresholds for a given climate zone.
**Context:** ENERGY STAR certification is frequently the qualifying condition for utility rebates and federal energy tax credits, so it affects the net cost of a project, not just its performance.
**Related terms:** U-Factor, SHGC, Low-E Glass

## Installation

### Flange (Nailing Fin)
**Definition:** A flat projecting lip around the exterior perimeter of a window frame that is fastened to the wall sheathing and integrated into the building's water-resistive barrier.
**Context:** The flange is what ties a window into the wall's drainage plane. Whether the new window needs one is the first and most consequential decision in a replacement project.
**Related terms:** Full-Frame Replacement, Insert Replacement, Water Penetration
**Royal connection:** Royal evaluates the wall and the existing window to determine whether a flange is required before specifying a unit.

### Full-Frame Replacement
**Definition:** A replacement method in which the entire existing window, including its frame, is removed down to the rough opening, and a new flanged window is installed and tied into the wall's water management.
**Context:** This is the correct method when the exterior walls are sided and no sound old wood frame will remain. It costs more and disturbs more of the wall, and it is the only way to install a flanged window properly.
**Related terms:** Insert Replacement, Flange, Rough Opening

### Insert Replacement (Pocket Replacement)
**Definition:** A replacement method in which a new non-flanged window is fitted inside the existing wood window frame, which stays in the wall undisturbed.
**Context:** This is only safe when the old wood frame remains in the wall, its connection to the wall is not disturbed, and the frame is not rotted. Fitting a non-flanged window where the wall actually requires a flange is one of the most common and most expensive installation errors.
**Related terms:** Full-Frame Replacement, Flange, Water Penetration

### Rough Opening
**Definition:** The framed opening in a wall into which a window or door unit is installed, sized slightly larger than the unit to allow for shimming and squaring.
**Context:** Accurate measurement of the rough opening determines whether a unit can be installed square and sealed properly.
**Related terms:** Full-Frame Replacement, Shim

### Water Penetration
**Definition:** Water entering a wall assembly around a window or door rather than being drained back to the exterior.
**Context:** This is the failure mode that turns a bad installation into a structural problem. Water that gets around the frame reaches the wall, rots the framing, and promotes mold growth inside the wall — often unnoticed until the repair is expensive.
**Related terms:** Flange, Full-Frame Replacement, Insert Replacement

### Air Infiltration
**Definition:** The rate at which air leaks through a window or door assembly, measured under conditions specified by ASTM standards and reported in cubic feet per minute per square foot.
**Context:** Manufacturer air infiltration numbers are produced on a perfectly installed unit in a test chamber. Field performance depends heavily on installation quality, so a good number on a data sheet does not guarantee a tight window in the wall.
**Related terms:** ASTM, Weatherstrip, Gasket, Casement Window

### ASTM
**Definition:** ASTM International, the standards organization whose test methods define how window and door performance — including air infiltration, water penetration, and structural load — is measured.
**Context:** ASTM methods are what make one manufacturer's performance numbers comparable to another's.
**Related terms:** Air Infiltration, U-Factor

## Hardware and Components

### Sash
**Definition:** The moving framed panel that holds the glass within a window's outer frame.
**Context:** In a double hung window, both sashes move. In a casement, a single sash swings out. Whether a sash can be removed determines whether glass-only replacement is practical.
**Related terms:** Insulated Glass Unit, Double Hung Window, Casement Window

### Weatherstrip
**Definition:** A compressible or pile seal fitted along the contact surfaces between a moving sash or door panel and its frame, to limit air leakage.
**Context:** Whether weatherstrips are removable is the single factor that determines whether an existing drafty double hung or slider can be improved. Windows with a single weatherstrip and a poor sash-to-frame fit generally cannot.
**Related terms:** Gasket, Air Infiltration, Q-Lon Weatherstrip

### Gasket
**Definition:** A continuous compressible seal that a sash or panel presses against when closed, sealing by compression rather than by sliding contact.
**Context:** Compression sealing is why casement windows generally outperform sliding styles on air infiltration. Casement gaskets are often not replaceable, which limits what can be done to an old unit.
**Related terms:** Weatherstrip, Casement Window, Air Infiltration

### Q-Lon Weatherstrip
**Definition:** A compressible foam-and-film weatherstrip fitted into a groove in a door frame, common on fiberglass and insulated steel entry doors.
**Context:** It is one of the easiest door seals to renew — the old strip pulls out of the groove and a new one pushes in, with no special tools.
**Related terms:** Weatherstrip, Door Sweep, Adjustable Threshold, Entry Door

### Door Sweep
**Definition:** A seal attached to the bottom edge of a door panel that closes the gap between the panel and the sill.
**Context:** A worn sweep is a common source of draft at the bottom of an entry door. Replacement difficulty varies with how the sweep is held to the panel.
**Related terms:** Adjustable Threshold, Sill, Q-Lon Weatherstrip

### Adjustable Threshold
**Definition:** A door sill with a raised section that can be adjusted up or down to tune the contact pressure between the door sweep and the sill.
**Context:** It is a marker of better-quality door units and the first thing to check when an entry door starts to feel drafty at floor level.
**Related terms:** Door Sweep, Sill, Entry Door

### Lockset
**Definition:** The complete locking hardware assembly on a door: handle or lever, latch, deadbolt, and strike.
**Context:** The lockset is the sixth and final decision in specifying an entry door, and it should match the style of the door — streamlined hardware on a modern door, more elaborate on a classic one. Options include keypad and phone-controlled electronic locks.
**Related terms:** Entry Door, Sidelite, Transom

### Sidelite
**Definition:** A narrow fixed glazed panel installed beside an entry door, on one or both sides.
**Context:** Sidelites bring daylight into an entry hall and change the proportions of the entrance. Adding them requires enough wall width beside the existing opening.
**Related terms:** Transom, Entry Door, Lockset

### Transom
**Definition:** A window unit installed directly above a door or another window, fixed or operable, often arched or rectangular.
**Context:** A transom raises the visual height of an entrance and adds light without widening the opening.
**Related terms:** Sidelite, Entry Door, Architectural Window

### Caming
**Definition:** The metal framework — typically brass, nickel, patina, or black finish — that holds decorative glass segments together in a leaded or decorative door glass panel.
**Context:** Caming finish is chosen to coordinate with the lockset and the exterior hardware.
**Related terms:** Lockset, Entry Door

### Spacer
**Definition:** The component that separates the panes of an insulated glass unit around the perimeter and carries the desiccant that keeps the sealed space dry.
**Context:** Warm-edge spacers made from low-conductivity materials reduce heat loss and condensation at the glass edge compared to older aluminum spacers.
**Related terms:** Insulated Glass Unit, Seal Failure, U-Factor

## Window Styles

### Double Hung Window
**Definition:** A window with two sashes in a single frame that slide vertically past one another, both typically operable and tiltable for cleaning.
**Context:** The most traditional and most requested window style on Long Island, suited to Colonial, Cape Cod, and Ranch housing stock.
**Related terms:** Horizontal Slider Window, Sash, Weatherstrip
**Royal connection:** Double hung is Royal's most requested window style.

### Horizontal Slider Window
**Definition:** A window whose sashes slide side to side within the frame rather than up and down.
**Context:** Sliders suit wide openings and walls where there is no vertical clearance for a double hung sash.
**Related terms:** Double Hung Window, Sash

### Casement Window
**Definition:** A window with a side-hinged sash that swings outward, operated by a crank.
**Context:** Because the sash compresses against gaskets when closed rather than sliding past weatherstrips, casements generally have better air infiltration performance than double hung or slider styles.
**Related terms:** Awning Window, Gasket, Air Infiltration

### Awning Window
**Definition:** A window with a top-hinged sash that swings outward from the bottom, forming an awning over the opening.
**Context:** Awnings can stay open in light rain and work well over sinks, counters, and other positions that are hard to reach.
**Related terms:** Casement Window, Fixed Window

### Fixed Window
**Definition:** A non-operating window unit that cannot be opened.
**Context:** Fixed units are the most airtight window type available, and differences between manufacturers are small because there is no moving seal to get wrong. They maximize glass area and view.
**Related terms:** Air Infiltration, Architectural Window

### Bay Window
**Definition:** A projecting assembly, typically of three units, that extends beyond the exterior wall plane at angles.
**Context:** A walk-in bay projects far enough to add usable floor area to the room.
**Related terms:** Bow Window, Garden Window

### Bow Window
**Definition:** A projecting assembly of four or more units set at shallow angles to form a curve.
**Context:** Bows widen the view from long or narrow rooms and read as a gentler curve than the angular projection of a bay.
**Related terms:** Bay Window, Casement Window

### Garden Window
**Definition:** A small projecting glass box with glazed sides, a glazed top, and an interior shelf.
**Context:** Most often installed over a kitchen sink, where the shelf is used for plants and the side vents provide ventilation.
**Related terms:** Bay Window, Fixed Window

### Architectural Window
**Definition:** A window manufactured to a non-rectangular shape — arched, circular, triangular, trapezoidal, or a custom combination — to fit a specific opening.
**Context:** Architectural shapes are where local manufacturing flexibility matters most, because they cannot be pulled from stock.
**Related terms:** Fixed Window, Transom, Rough Opening
**Royal connection:** Royal manufactures architectural and custom-shaped windows to the opening at its Bay Shore factory.

## Door Types

### Entry Door
**Definition:** The main exterior door of a house, specified as a complete unit including the panel, frame, sill, weatherstripping, glass, and hardware.
**Context:** An entry door is specified across six decisions: layout, material, amount and shape of glass, type of glass, color or finish, and lockset.
**Related terms:** Sidelite, Transom, Lockset, Fiberglass
**Royal connection:** Fiberglass entry doors are Royal's most configurable product line.

### Sliding Patio Door
**Definition:** A glazed exterior door with one or more panels that slide horizontally within a track, past fixed panels.
**Context:** Sliding doors suit openings where there is no room for a panel to swing, and are available in wide multi-panel configurations and with blinds enclosed between the glass.
**Related terms:** Swing Patio Door, Insulated Glass Unit

### Swing Patio Door
**Definition:** A glazed exterior door with hinged panels that swing open, in single, double, or multi-panel configurations, often with sidelites and transoms.
**Context:** Swing doors seal by compression and generally outperform sliding doors on air infiltration, but need clear floor space for the swing.
**Related terms:** Sliding Patio Door, Gasket, Transom

### Storm Door
**Definition:** A secondary exterior door installed in front of an entry door, typically with interchangeable glass and screen panels.
**Context:** On Long Island a storm door adds a layer of weather protection against nor'easters and coastal exposure, and protects the finish of the entry door behind it.
**Related terms:** Entry Door, Door Sweep
**Royal connection:** Royal carries Elmont and Provia storm door lines.

## Business Terms

### Factory-Direct
**Definition:** A sales model in which the manufacturer sells its own products to the end customer, without a master distributor, regional distributor, or dealer in between.
**Context:** Each distribution layer carries its own margin, so the number of layers between the plant and the house materially affects the price of the same product.
**Related terms:** Manufacturer, Distributor
**Royal connection:** Royal manufactures at its Bay Shore factory and sells directly to homeowners, architects, builders, and contractors, removing one to two layers of distribution.

### Full-Service Manufacturer
**Definition:** A window and door company that handles the entire sequence — advice, measurement, design, sales consultation, manufacturing, installation, and after-sale support — rather than one part of it.
**Context:** When one organization is responsible for both the product and the installation, a failure cannot be passed between vendors.
**Related terms:** Factory-Direct, Full-Frame Replacement
**Royal connection:** Royal offers the full sequence, and will also manufacture and deliver units for an installer the customer chooses.

### Builder Grade
**Definition:** A lower-specification tier of a product line, made to a price point for volume construction rather than to a performance target.
**Context:** Homeowners frequently discover after the fact that the windows in a house are a builder-grade version of a recognizable brand name, which is why brand alone is a weak proxy for quality.
**Related terms:** Factory-Direct, uPVC
**Royal connection:** Royal manufactures a single top-grade series and has no builder-grade tier, which is also why it does not compete for commodity construction work.