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Glossary of Home Improvement Terms




American Architectural Manufacturers Association. A national trade association that establishes voluntary standards for the window, door, storefront, curtain wall and skylight industries.

Air infiltration

The amount of air leaking in and out of a building through cracks in walls and windows.

Argon gas

An inert, nontoxic gas used in insulating glass units to reduce heat transfer.


American Society for Testing and Materials. Organization that develops methods for testing of materials.

Awning window

A window that is hinged at the top and swings outward for ventilation. See our Awning Windows.

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A flat material used on the face of the house, between the studs and the siding, to provide a nailable surface for the siding.

Balance covers

A snap in covering that conceals the ConstantForce™ balance system within the window frame, helping to keep dirt and dust out of the chamber.

Bay window

An angled combination of three windows that project out from the wall of the home. The windows are usually positioned at 30- or 45-degree angles. See our Bay Windows.

Beveled MasterFrame

Some Alside windows feature a unique fusion-welded design that accommodates differing installation methods and architectural styles. It is the angled portion of the masterframe profile that adds a three dimensional appearance to the exterior of the window.

Block and Tackle Balance System

The block and tackle system utilizes a high-density nylon cord pulley action which is attached to a moveable block that travels up and down within a metal chamber. Tension from a heavy duty coil spring at the top of the block creates the proper resistance necessary for smooth operation of the window sash.

Bow window

An angled combination of windows in 3-, 4- or 5-lite configurations. As the windows are joined to each other, they combine to form an arch shape that projects from the wall of the home. See our Bow Windows.


The bottom edge of a siding or soffit panel, or accessory piece, opposite the nailing slots, which locks onto the preceding panel.


A rubber material that seals the glass to the spacer, creating an airtight and water-tight insulated glass unit.

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Cam-action lock and keeper

The mechanisms, which pull and secure the sashes together when placed in the locked position.

Casement window

A window with a side-hinged sash that opens and closes outward by a crank handle mechanism. Available in continuous mainframe, with multi-lite configurations. See our Single Casement Windows.


The area of the accessory trim or corner post where siding or soffit panels are inserted. Channels also refer to the trim itself, and are named for the letters of the alphabet they resemble (e.g., J-channel, F-channel, etc.).

ClarityOne Glass

A chemical treatment that when applied to glass, helps to create a smoother surface that won’t attract or hold dirt and dust. Established by PPG Industries.


The brand name for the insulated glass unit that is present in Alside’s insulating glass packages. A ClimaTech unit will contain either two or three panes of glass, with one or two of those panes being a Low E surface. It will utilize the SST warm edge spacer system and contain either argon or krypton gas.


The deposit of water vapor from the air on any cold surface whose temperature is below the dew point, such as a cold window glass or frame that is exposed to humid indoor air.


A row of panels, one panel wide, running the length of the house from one side to the other, or, in the case of vertical siding, from top to bottom.

Coved glazing beads

A contoured piece of vinyl that holds the glass in place within the sash and adds an elegant, finished look.

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Double-hung window

A window that has two vertical operating sashes. See our Double Hung Windows.

Double Channel Lineal

A siding accessory that joins two soffit panels.

Drip Cap/Head Flashing

An accessory installed with vertical siding to ensure that water drips away from panels and does not infiltrate them; it is also used as a vertical base.

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Brand name for specially coated, operating hardware that helps to resist oxidation and corrosion.

Egress Code

The minimum opening of a window for people to exit or firefighters to enter a building/dwelling. Different states or regions have different code requirements.

Energy Star®

The Energy Star program is a joint venture between the US Environmental Protection Agency (EPA) and the US Department of Energy (DOE) designed to encourage homeowners to purchase energy-efficient products. Using less energy in our homes reduces the amount of CO2 emissions released into the atmosphere from burning fossil fuels such as coal, oil and natural gas. The advanced components and design in the ClimaTech™ insulated glass package exceed all performance criteria required by the Energy Star program. A proud Energy Star Partner.


Alside’s brand name for its balance system. A balance system is a device for holding the vertically sliding sashes in any desired position within the window mainframe.

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Refers to the side of a siding or soffit panel that is showing once the panel has been installed.


The action of fastening directly onto the 'face' side of a panel (instead of using the nail hem slot). This practice is generally not used in siding installation.

Fascia Board

A board attached to the ends of the rafters between the roofing material and the soffit overhang. Fascia cap is the covering around that board.


The placement of window openings in a building wall, one of the important elements in controlling the exterior appearance of a building. Also, a window or skylight and its associated interior or exterior elements, such as shades or blinds.

Fixed Lite

A pane of glass installed directly into non-operating framing members; also, the opening or space for a pane of glass in a non-operating frame.

Fixed Panel

An inoperable panel of a slider window.

Fixed Window

A window with no operating sashes. A picture window is an example of a fixed window.


A thin, flat material, usually aluminum, positioned under or behind J-channels, corner posts, windows, etc., to keep draining water from penetrating the home.

Furring/Furring Strip

A wooden or steel framing material, usually 1" x 3", used to provide an even nailing base. To “fur” a surface means to apply these strips.


The process of joining materials by melting them together with extreme heat (in most cases over 500ºF), resulting in the materials combining into a one-piece unit.

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Garden window

Designed much like a bay or bow window, a garden also extends from the wall to the exterior of the home. It is built in a square or rectangular shape at right angles. The two side lights often operate for added ventilation. See America's Window's Garden Windows.

Gas Fill

A gas other than air, usually argon or krypton, placed between window or skylight glazing panes to reduce the U-factor by suppressing conduction and convection.


The glass or plastic panes in a window, door or skylight.

Glazing Bead

A molding or stop around the inside of a window frame to hold the glass in place.


Optional horizontal or vertical lineals installed between the glass panes help to create the appearance of a divided window design.

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Hopper window

A bottom-hinged sash window that opens inward for ventilation. See America's Window's Basement Windows.

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Insulating air chambers

Various chambers within the sash and masterframe, which help to insulate and strengthen the window.


The fusion-welding process of some Alside windows.

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A vertical member at the side of a window frame or the horizontal member at the top of the window frame, as in head jamb.

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Krypton gas

An inert, nontoxic gas used in insulating windows to reduce heat transfer.

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To overlap the ends of two siding panels or accessory pieces to allow for expansion and contraction of the vinyl product.

Lift Handle

Used to raise the lower sash in a double-hung window. Also called sash lift.


A unit of glass in a window.

Low E (Emissivity) Glass

Microscopically thin, virtually invisible, metal or metallic oxide layers deposited on a window or skylight glazing surface primarily to reduce the U-factor by suppressing radiative heat flow. A typical type of low-E coating is transparent to the solar spectrum (visible light and short-wave infrared radiation) and reflective of longwave infrared radiation.


The raised 'ears' or tabs on a siding panel, created by a snaplock punch, which can be used to lock a siding panel into place when the nailing hem has been removed.

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The combination of the head, sill and jamb sections of a window.

Meeting rail

The part of a sliding window or a hung window where two panels meet and create a weather barrier.


To make a diagonal cut, beveled to a specific angle (usually 45°). Sometimes miter cuts are made into an overlapping siding or soffit panel surface, to provide a neater appearance.


A weatherstripping material that is present where the sash frame meets the masterframe. Adds increased resistance to air infiltration.

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Nailing Hem (or Flange)

The section of siding or accessories where the nailing slots are located.


National Fenestration Rating Council.

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Obscure glass

Glass that has been made translucent instead of transparent.

Origin II™

The virgin uPVC vinyl used in all Alside windows. The material’s low thermal conductivity makes it the best choice for window manufacturing. Will not rot, peel, blister, swell or deteriorate from corrosion or pitting.

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Picture window

A picture window that does not move or operate.A picture window is an example of a fixed window.


A position or measurement that is truly and exactly vertical, 90° from a level surface.

Positive Lock

Area below the nailing hem that the buttlock locks into.


Describes the design of the panel (Clapboard, Dutch lap, Triple 3, etc.)

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A measure of the resistance of a glazing material or fenestration assembly to heat flow. It is the inverse of the U-factor (R = 1/U) and is expressed in units of hr-sq ft-ºF/Btu. A high-R-value window has a greater resistance to heat flow and a higher insulating value than one with a low R-value.


The transfer of heat in the form of electromagnetic waves from one separate surface to another. Energy from the sun reaches the earth by radiation and a person’s body can lose heat to a cold window or skylight surface in a similar way.

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Separate from the masterframe, the portion of the window that contains the glass.

Sash limit locks

A feature that allows a window to be safely raised to a certain height.


Running a utility knife blade, a sharpened awl, scoring tool, or other sharp implement across a soffit or siding panel face without cutting all the way through the panel. This weakens the vinyl surface in a specific area and allows the panel to be bent and broken off cleanly.


The horizontal, bottom section of the masterframe.

Sliding Window

A window in which the sashes move horizontally. Available in a 2- or 3-lite configurations. America's Window has a wonderful selection of Sliding Windows.


Material used to enclose the horizontal underside of an eave, cornice, or overhang. Some soffit panels may also be used as vertical siding.

Solar Heat Gain Coefficient (SHGC)

The fraction of solar radiation admitted through a window or skylight, both directly transmitted and absorbed and subsequently released inward. The solar heat gain coefficient has replaced the shading coefficient as the standard indicator of a window’s shading ability. It is expressed as a number between 0 and 1. The lower a window’s solar heat gain coefficient, the less solar heat it transmits and the greater its shading ability. SHGC can be expressed in terms of the glass alone or can refer to the entire window assembly.


An object placed between two or more pieces of glass which helps to maintain a uniform width between the glass, and prevent sealant distortion.


A measurement of siding. One square equals 100 square feet (10 x 10 wall).

SST non-metal spacer

A solid silicone foam spacer covered with Mylar. It is sealed to the edge of the glass and then sealed with butyl for greater energy efficiency.


A flexible framing material used to even a surface prior to installation.

Starter Strip

An accessory applied directly to the surface of the building and used to secure the first course of siding to the home.

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TrueCapture™ Sloped Sill

The sill of some Alside double-hung windows that has a downward slope toward the outside with a capture dam that helps to keep water from infiltrating the base of the bottom sash. Sloped sill assists water drainage to the exterior of the window.

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Weather-resistant material placed under vinyl siding panels.

UV (Ultraviolet light)

The invisible rays of the spectrum that are outside of the visible spectrum at its short-wavelength violet end. Ultraviolet rays are found in everyday sunlight and can cause fading of paint finishes, carpets and fabrics.

UV reflection

The percentage of ultraviolet rays being blocked rather than being transmitted through the window’s glass unit. The higher the number, the lower the percentage of ultraviolet rays being transmitted through the window.

U-value (U-factor)

A measure of the rate of non-solar heat loss or gain through a material or assembly. It is expressed in units of Btu/hr-sq ft-ºF (W/sq m-ºC). Values are normally given for NFRC/ASHRAE winter conditions of 0ºF (18º C) outdoor temperature, 70º F (21º C) indoor temperature, 15 mph wind and no solar load. The U-factor may be expressed for the glass alone or the entire window, which includes the effect of the frame and the spacer materials. The lower the U-factor, the greater a window’s resistance to heat flow and the better its insulating value.

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Visible Light

The portion of the electromagnetic spectrum that produces light that can be seen. Wavelengths range from 380 to 720 nanometers.

Visible transmittance (VT)

The percentage or fraction of the visible spectrum (380 to 720 nanometers) weighted by the sensitivity of the eye that is transmitted through the glazing.

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Warm-edge technology

The use of low-conductance spacers to reduce heat transfer near the edge of insulated glazing.


Material used to form a weather-resistant seal around operable sash.

Weep Holes

Openings cut into siding or accessories to allow for water runoff.

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