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American Architectural Manufacturers Association. A national trade association that establishes standards for the window and door industry. Always look for AAMA certified products when purchasing your windows and doors.


The amount of air leakage in and out of a building through cracks in walls, doors, and windows, a major source of energy loss in a building envelope.

Aluminum Clad

 Window or Doors of wood construction covered on the exterior with aluminum to protect the wood frame form warping.  Can be roll-formed or extruded, the extruded is heavier and more structural. General with a factory finish to deter against the elements.

Argon Gas

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


American Society for Testing and Materials, organization that develops methods for testing materials.


The center member of a double door unit, which is attached to the fixed or inactive door panel, and allows for better weathershipping and security.

Awning Window

A window that is hinged at the top and swings outward for ventilation.

Back Bead

A term that applies to a sealant or caulk around the old window frame or opening to seal and adhere the new window in place. To assure a weather tight seal.

Balance – (Sash Balance)

A device for counterbalancing a sliding sash, usually in a single or double hung window, so that the sash will stay open. Usually a system of cords, weights, springs, spiral devices or block and tackle hardware.

Bay or Bow Window

An arrangement of 3 or more individual window units, attached so as to project from the building at various angles.

Brake Metal

Using an aluminum trim or brake metal around a retro fit install, not used much today as the aluminum can fail, and the many gaps that can lead to air and water infiltration as well as the aluminum failure. This was one of the first ways to do retro fit windows prior to the window manufacturers coming up with a true retro fit window with a continuous flush fin. The least effective type of install also the cheapest.

Brickmold or Birckmould

A standard exterior trim piece that covers the gap between the frame and the building wall.

BTU (B.T.U.)

An abbreviation for British Thermal Unit, the heat required to increase the temperature of one pound of water one degree Fahrenheit.

Cam-Action Lock & Keeper

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


Lead strips which bond small pieces of decorative glass in windows.

Casement Window

A window with a side hinge sash that opens and closes outward by a crank handle mechanisms, available in right hand and left hand.


Molding or trim applied around a window or door to cover the space between the frame and the wall, available in many profiles, widths, and materials.


A mastic compound for filling joints and sealing cracks to prevent leakage of water and air. Commonly made of silicone, bituminous, acrylic, rubber based material, or the newer poly based products designed for the vinyl industry.


Cubic Feet per Minute manly used to describe leakage of air.

Check Rail

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

Circle Top

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


Usually an aluminum or vinyl material fixed to the outside faces of a wood windows and doors to provide a durable, low-maintenance exterior surface.


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 humidity inside or outside.

Crank Handle

A handle that attaches to an awning or casement operator, used to open the venting window.


Condensation Resistance Factor. An indication of a window’s ability to resist condensation. The higher the CRF, the less likely condensation is to occur. Based on AAMA standard.

Double Glazing / DG

In general, two thicknesses of glass separated by an air space within an opening to improve insulation against heat transfer and or sound transmission. In factory made double pane units the air between the glass sheets is hermetically sealed and is air tight, eliminating possible condensation and providing superior insulation.

Double Hung Windows / DH

A window that has two vertical sash that are both operable the bottom slides up and the top slides down.

Drip Cap

Horizontal exterior molding to divert water from the top casing so water drips beyond the outside of the frame

Drop In Windows

Refers to replacement windows in old wooden frames due to the nature of the install.

Egress Code / Egress Window

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

Energy Star

The Energy Star program is a joint venture between the U.S. Environmental 

Protection Agency (EPA) and the U.S. Department of Energy (DOE) designed to encourage homeowners to purchase energy-efficient products. Using less energy in our homes, by utilizing Low-e2 or the new Low-e3 insulated glass that exceed all performance criteria required by Energy Star Program. 

Extension Jamb

A board used to increase the depth of the jamb of a window frame to fit any wall condition or given thickness.


The process of producing vinyl or aluminum shapes by forcing heated material through as orifice in a die, high quality vinyl windows use stainless steel dies to produce a smooth surface without lines and grooves that can be visible and detract from the window or door.

Expanding Foam Sealant

Uses to fill gaps when installing windows and doors. Can fill small voids and air pockets and used as additional layer to prevent air and water infiltration, also for sound control.


The placement of window or door openings in a building wall, or building envelop, one of the important elements in controlling the exterior appearance of a building.

Finger Joint

A wood end-joint formed by a set of interlocking fingers, coated with adhesive and mashed together under pressure to form a tight bond.

Fixed Panel  / “O” Panel

An inoperable panel of a sliding glass door or a slider window.

Fixed Window

A non-operable window sometimes call a picture window.

Flush Fin

An integrated retro fit fin around the window unit. The vinyl window manufacturers came up with this to prevent leakage as associated with the old break metal process. The most effective way to prevent air and water infiltration in a retro fit window or door.


An enclosure or combination of parts which is surround a window sash or door panel.

French Doors

A two panel door system where both panels operate, available in swing-in or swing-out.

French Sliding Door

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

Fusion Welded

The process of joining material by melting them together with extreme heat resulting in the materials combining into one piece forming a unit, such as the corners of vinyl windows. This is the preferred method which most major vinyl window and door manufacturers use today. This method forms a stronger, leak proof joint. Sometimes referred to as a welded frame by the vinyl window industry.

Garden Window / Greenhouse Window

Designed much like a bay or bow window, a garden window extends from the wall to the exterior of the home. Most have a rectangular shape with a glass top and side ventilation. Used primary over a kitchen sink area to add light and volume.


The glass panes in a window or door. Many options are available to suit individual requirements.

Glazing Bead

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


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

Grille or Muntin Bar

Usually removable for easy cleaning, grilles give the appearance of  divided window panes.


Supporting member or beam above a window or door opening which transfers building weight above to the supporting wall structure on each side of the opening.

Heat Gain

The transfer of heat from outside to inside or inside to outside by means of conduction and radiation through all surfaces of a home.

Hinged Doors

Similar to French Doors where the door swings inside or swings outside.

Horizontal Slider

A window with a movable panel that slides horizontally, such as an XO, OX, or XOX where the X panel is the operable sash. Generally as viewed from outside when referred to window and door handing.


See Air-Infiltration

Insulating Glass

Two or more pieces of glass spaced apart and hermetically sealed to form a single IG unit, also call double pane glass.


The frame member between the operable and fixed panels which engages to prevent water and air infiltration and added weather-stripping. Most meet forced entry requirements set forth by AAMA if the window unit is AAMA certified.


 The vertical members at the side of a window or door frame.

Jamb Liner

The plastic or metal track installed in the jambs of the window in which the window sash slide.


The hooked shaped piece of hardware that it is mounted on the inside sash stile of a casement window in which the sash lock engages.


A term for thermal insulation value or coefficient of thermal conductivity. Which is the amount of heat that passes through a cube of material in a given time. Used to compare different window frame materials for energy efficiency. The best way to compare energy efficiency. The lower the number the better the thermal properties are, vinyl windows have a low K-Factor. Aluminum is around

1600  K-factor where as vinyl is about a  1  K-Factor.

Laminated Glass

Similar to the construction of car windshields, this technique sandwiches a piece of transparent film or plastic between two panes of glass, typically used for safety  reasons because of its resistance to shattering. Also reduce noise transmission to the interior.

Lite / Light

A unit of glass in a window or door.

Low-E / Lowe2 /  Lowe3 / (Low Emissivity glass)

Microscopically thin, virtually invisible, metal or metallic oxide layers or coatings deposited on a window glazing surface primarily to reduce U-factor by a reduction of radiant heat transfer and heat flow.  A typical Low-E coating is almost transparent allowing visible light transfer and reflecting infrared radiation. Almost 4 times more energy efficient than old single pane glass. 

See Energy Star.


Laminated Veneer Lumber – A combination of many pieces of veneered lumber glued together to give added structural capabilities. Often used in window or door frames.

Meeting Rail

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


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

Mullion / Mull

A structural vertical or horizontal member between window units or sliding glass doors. The process of joining multiple units for installation in the same rough opening. Sometimes called a Mulled unit.


Vertical or horizontal bars used to separate glass in a sash into multiple lights.

Nailing Fin

An integral extension of a window or patio door frame which generally laps over the conventional stud construction and through which nails are drive to secure the frame in place during installation.


National Fenestration Rating Council.

Obscure Glass

A glass that has been made translucent instead of transparent. Any textured glass, frosted, etched, fluted, ground, glu-chip, ect. Used for privacy, light diffusion or decorative effect.

Operable Window

A window that can be opened for ventilation.


A crank operated device for opening and closing casement or jalousie windows.


A major component of a sliding glass door or window, consisting of the frame and glass installed within the main frame, a panel maybe fixed or sliding.

Perimeter Caulk

This is the sealant around the outside of the window or door frame adding an additional layer of sealant against the building to prevent air and water infiltration.

Picture Window

A picture window is a fixed non-operable window

Polyurethane Sealant Adhesive

One of the new adhesive sealants on the market manufactured for the vinyl window industry, for it superior holding power, and leak prevention. Although more costly it is far superior to silicone and latex caulking as an adhesive and sealant.

Polyvinylchloride / PVC

An extruded or molded plastic material used for window framing and thermal barrier for windows and doors. Often referred to as Vinyl Windows and Doors. Not all vinyl is the same for more information refer to Mikron vinyl’s web site.


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. A high R-Value window has a greater resistance to heat flow and higher insulating value than a low R-Value.


The horizontal or vertical member of the window sash.

Retrofitting / Retro-fit

Adding or replacing windows and doors on an existing building. Typical Retrofit products are replacement doors and windows. With the new vinyl doors and windows Retrofitting has become a cost effective way to add energy efficiency and upgrade your home. Sometimes call replacement windows or drop in windows. Generally this type installation does not need stucco or drywall patch and very rarely needs painting.

Rough Opening

The opening in a wall into which a door or window is to be installed. Generally used to describe a term in rough framing or new construction.

Safety Glass

A strengthened or reinforced glass that is less subject to breakage or splintering such as tempered glass. Required in hazardous locations such as next to doors, stairways, in showers, tubs or close to the floor. Please check local code requirements.


Separate form the mainframe, the portion of the window that contains the glass.


A woven mesh of metal or fiberglass stretched over a window opening to permit air to pass through, but not insects.

Seat Board

A flat board cut to fit the contour of a bay or bow window and installed between the sill and the wall surface, providing a seat or a shelf space for plants, ect.

Shading Coefficient  (SC)

A measure of the ability of a window to transmit solar heat. It is being phased out in favor of the Solar Heat Gain Coefficient.

Side Light

A fixed or venting, often a narrow glass window next to a door opening or window openi


The horizontal bottom section of the mainframe in a window unit.

Simulated Divided Lights

A method in constructing windows or doors in which muntins are fixed to the inside and outside of the insulated glass panels to simulate the look of true divided light.

Single Glazed

Single thickness of glass in a window and door, rarely used today as most glazing in today’s market is at least double pane and in most cases is Lowe2 due to energy requirements. See Energy Star & Low-E.

Single Hung Windows

A window consisting of two sashes of glass, the top one is stationary and the bottom is movable.

Sliding Window

A window fitted with one or more sashes opening by sliding horizontally in the mainframe sometimes call slider windows, or horizontal sliders.

Smash Out windows

Refers to replace of old steel or aluminum casement windows where the glass has to be broken out (smashed out) to replace. One of the harder retro fit install applications.

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 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 along or can refer to the entire window assembly.

Sound Transmission Class   (STC)

The Sound Transmission loss rating of a material over a selected range of sound frequencies. The higher the number, the less sound transmitted.  Be careful not to exceed the wall STC with the Window STC as you can sometime get more sound through the wall if you use a too high STC window product. Sound reduction is becoming more important in window selection in today’s market.


An object placed between two or more pieces of glass to maintain a uniform width between the glass panes, and prevent sealant distortion. Used to form a dead air space between glass panes for added energy efficiency and sound reduction.


The upright or vertical edges of a door or window.


An interior trim on a window which extends the sill and acts as a narrow shelf. Often seen on double or single hung windows.

Tempered Glass / Safety Glass

Treated glass that is strengthened by reheating it to just below the melting point and then suddenly cooling it. When shattered it breaks into small pieces. Approximately five times stronger then standard annealed glass. It is required as a safety glazing in patio doors, entry doors, side lights, shower doors, and other hazardous locations.


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

Thermal Break

A thermal insulating barrier between two thermally conductive materials.

Tinted Glass

Glass colored by incorporation of a mineral admixture. Any tinting reduces both visual and radiant transmittance. Used to block sun glare more than heat do to the new Lowe3 glazings on the market today.


A small window located above a door or window.

U-Factor  (U Value)

A measure of the rate of non-solar heat loss or gain through a material or assembly. It is expressed in units. Values are normally given for NFRC / ASHRAE winter conditions of 0 degrees F outdoor temperature 70 degrees F indoor temperature 15 MPH wind and no solar load. The U-Factor may be expressed for the glass alone or the entire window. The lower the U-Factor the greater a window’s resistance to heat flow and the better its insulation value.

Ultraviolet Light  (UV)

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. An ancillary benefit of Low-E glass is the reduction in UV light.

Venting Unit

A window or door that operates or opens for ventilation.


Polyvinyl Chloride Material or PVC, which can be both rigid and flexible, used for window frames, pure vinyl or PVC is non-biodegradable and can last a lifetime with virtually no maintenance. One of the latest technologies used to make high quality windows and door today due to its durability and energy efficiency. See K-Factor

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 resistance seal around operable sash. Prevents water and air infiltration. (major cause of energy loss in a home)

Weep Hole

A small opening in a wall or window sill member through which water may drain to the building exterior. Prevents water from pooling up in window frame or tracks.


The force exerted on the surface by moving air.


A glazed opening in an external wall of a building, an entire unit consisting of a frame, sash, and glazing, and any operable elements. Sometime referred to as a window unit or basic unit.