Windows Definitions

Window Definitions and Terms

• Air Chambers – Small honeycomb spaces within the sash and frame which helps to insulate and

strengthen the window

• Argon Gas – An odorless, colorless, tasteless, non-toxic gas which is six times more dense than

air. It is used to replace air between the glass panes to reduce temperature transfer.

• Awning – A top-hinged window that swings outward for ventilation.

• Bay Window – An angled combination of three windows that project out from the wall of the

home. The windows are commonly joined at 30- or 40-degree angles.

• Cam Lock and Keeper – The mechanisms which pull the sash together when placed in the locked


• Capillary Tubes – Small hollow tubes which penetrate the spacer system of an insulating glass

unit. They allow pressure equalization between manufacturing locations, shipping, and

installation locations. Since the insulating glass unit is not permanently sealed, the air space

cannot be filled with Argon gas.

• Casement – A window with a side-hinged sash that opens outward for ventilation.

• Celcon® Rollers – Self-lubricating rollers that are found in slider windows and patio doors, that

will not mar and are corrosion resistant.

• Condensation Resistance Factor – A measure of the effectiveness of a window or glazing system

to reduce the potential for condensation. The higher the condensation resistance factor, the

more efficient the window and glazing system.

• Conduction – Energy transfer from one material to another by direct contact.

• Constant Coil Spring Balance System – Device for holding vertically sliding sash in any desired

position through the use of a spring or weight to counterbalance the weight of the sash.

• Convection – Heat transfer by currents that flow from a warm surface to a colder one.

• Coved Exterior – An arced extension from the frame that adds an aesthetically pleasing

dimension to the exterior of the window.

• Dead-Air Space – The space between the panes of glass of an IG unit.

• Double Hung – A window that has two operable sash which slide vertically.

• Double Strength Glass – Glass with a thickness of approximately 1/8”

• Egress Code – The code that requires a minimum opening of a window for persons to exit or

firefighters to enter a building.

• Extruded Screen Frame – Different from a Rollformed frame, this frame is pressed through a

form or die.

• Fusion-Welded – The process of joining materials by melting them together with extreme heat

(over 500° F), resulting in the materials uniting into a one-piece unit.

• Geometric – Specially designed windows classified as either Straight Line Geometrics such as

rectangles, triangles, trapezoids, octagons, pentagons, etc., or Radius Geometrics which include

half-rounds, quarter-rounds, circles, ellipses, eyebrows, etc.

• Glazing – The process of sealing the glass to the sash

• Grids (or Grilles) – Decorative horizontal or vertical bars installed between the glass panes to

create the appearance of the sash being divided into smaller lites of glass.

• Insulating Glass Unit (or IG Unit) – Two or more lites of glass separated by a spacer and

hermetically sealed at the glass edges.

• Intercept® Spacer System – A spacer system using a U-channel design to reduce the number of

conduction paths.

• J-Channel – Integral extension on the outside of a new construction window that eases

installation on siding applications.

• Jamb – Vertical sections of the main frame.

• Keeper Rail – The horizontal section of the sash where the keeper is attached.

• Keeper Stile – The vertical section of the sash where the keeper is attached.

• Laminated Glass – Specially designed glass where two panes of glass are bonded to a durable

interlayer, providing increased safety, UV protection and noise reduction. If the window or door

gets broken the glass will adhere to the plastic interlayer, preventing glass fallout in the home.

• Lap-Lok® Meeting Rail – Simonton’s patented meeting rail which overlaps and interlocks both


• Lift Rail – A handhold for raising and lowering the sash. Rail implies that the handhold is

continuous across the sash.

• Lite – A unit of glass in a window.

• Lock Rail – The horizontal section of the sash where the cam lock is attached.

• Lock Stile – The vertical section of the sash where the cam lock is attached.

• Low E (Emissivity) Glass – Glass with a transparent metallic oxide coating applied onto or into a

glass surface. The coating allows short-wave energy to pass through but reflects long-wave

infrared energy which improves the U-value.

• Main Frame – The head, sill and jambs sections of a window.

• Mechanically Fastened Frame – Refers to frames fastened with screws.

• Meeting Rail – The horizontal sections of a pair of sash that meet when the sash are closed.

• Meeting Stile – The vertical section of a pair of sash that meet when the sash are closed.

• Mullion – A vertical or horizontal connecting unit between two or more windows.

• Nailing Fin – An extrusion attached to the main frame of a window used to secure the unit to

the rough opening.

• Obscure Glass – Glass that has been made translucent instead of transparent.

• Overlapping and Interlocking Meeting Rail – A patented meeting rail which overlaps and

interlocks both sash.

• Patio Door – A glass door that slides open and close on adjustable tandem rollers. Available in

2- or 3-lite configurations with the operable panel available in any position.

• Picture – A window that has no moveable sash.

• Pivot Alignment System – An exclusive hinge-type system used on hung windows. This system

attaches the sash to the balance, creating perfect alignment between the sash and frame, while

allowing the sash to tilt inward for cleaning.

• Power Seal Spacer SystemTM or True-Dual Seal – A high performance spacer system based on

four independent design featuring a U-channel intercept spacer dual-sealed with urethane

adhesive and a hot melt butyl and an additional desiccant matrix within the spacer cavity.

• R-Value – Resistance a material has to heat flow. The higher the R-value, the greater the


• Rail – The horizontal sections of the sash.

• Raised Exterior – An angled extension from the frame that adds an aesthetically pleasing

dimension to the exterior of the window.

• Relative Humidity Condensation Point – The relative humidity level at which visible water vapor

or other liquid vapor begins to form on the surface of the sash or frame, based on an inside

temperature of 70°F and an outside temperature of 0°F. The higher the percentage, the more

moisture the air can hold before condensation will occur.

• Rollformed Screen Frame – A method of fabrication in which a flat (usually metal) material is

placed on a machine where the material is formed into shape using differently shaped rollers

and pressure.

• Sash – The part of the window which contains the glass.

• Shading Coefficient – The ratio of solar heat that is transferred through a glazing material

relative to the solar heat transferred through 1/8” clear glass. The lower the number, the more

efficient the window is at reducing solar heat gain.

• Sill – The horizontal, bottom section of the main frame.

• Simonton Sill® – An exclusive triple-stepped, sloped sill design.

• Slider Window – A window in which the sash move horizontally. Sliders are available in a 2- or

3-lite configuration, with the 3-lite having operable end vents.

• Sloped Sill – The sill of the window that has a downward slope to the outside. This sill has

sufficient degree of slope to aid in water runoff.

• Solar Heat Gain Coefficient – The percentage of heat gained from both direct sunlight and

absorbed heat. The smaller the number, the greater the ability to reduce solar heat gain.

• Spacer (or Spacer System) – Material placed between two or more pieces of glass in order to

maintain a uniform width between the glass, and prevent sealant and distortion.

• Stucco Fin – An extrusion used in stucco home installations that is attached to the main frame to

create a smooth, finished look for both the window and the stucco.

• Tempered Glass – Glass with a surface compression of not less than 10,000 psi, or an edge

compression of not less than 9,700 psi. When broken, the glass breaks into pebbles instead of


• Tilt Latch – Mechanism that unlocks the sash and allows it to tilt in from the main frame.

• Tilt-In/Lift-Out Sash – A sash that can be tilted to the interior and removed for cleaning and is

manufactured by welding.

• U-Value – Amount of heat transferred through a material. The lower the U-value, the slower

the rate of heat flow and the better then insulating quality.

• UV Block – The percent of ultraviolet rays blocked from being transmitted through the glass.

The higher the number the lower the percentage of ultraviolet rays transmitted through the


• Visible Light Transmittance – The percentage of light that is transmitted through glass in the

visible light spectrum (380 to 720 nanometers). The higher the number the higher the

percentage of visible light transmitted through the window.

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

• Weep Slots – Slots or holes in the sill (bottom) member of the sash frame that allows water to

escape. Weep flaps add a vinyl flap to keep insects out.