FAQ - Terminology

Air Chambers

Air Infiltration

Argon Gas

Awning Window

Balance Covers

Bay Window

Butyl

Cam Lock and Keeper

Casement Window

Center of Glass U- and R- Values

Condensation Resistance Factor

Conduction

Convection

Dead-Air Space

Desiccant

Double Hung Window

Energy Star

Fusion-Welded

Geometric

Glass

Glazing

Glazing Bead

Grills/Grids

Head

Head Expander

I.G. Unit (Insulating Glass Unit)

Intercept

Jamb

Keeper Rail

Keeper Stile

Krypton Gas

Lift Handle

Lift Rail

Lite

Low E (Emissive) Glass

Main Frame

Mechanically Fastened Frame

Meeting Rail

Mullion

Obscure Glass

Patio Door

Picture Window

R-Value

Radiation

Sash

Sill

Sill Extender

Slider Window

Sloped Sill

Spacer

Stile

Tempered Glass

Tilt Latch

Total U- and R- Values

U- Value

Visible Light Transmittance

Weather-Stripping

Weep Holes

What terminology should I become familiar with?

When replacing the windows in your home, you may be faced with a number of terms and phrases that are unfamiliar. Nobody should make you feel uncomfortable by using language that leaves you wondering what they mean.

Here are some terms that you should be familiar with...

• Air Chambers

  - Small honeycomb spaces within the sash and frame which help to insulate and strengthen the window

• Air Infiltration

  - The amount of air that passes between a window sash and frame. In windows it is measured in terms of cubic feet or air per minute, per square foot of area. The lower the number, the less air the window lets pass through.

• 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 Window

  - A top-hinged window that swings outward for ventilation.

• Balance covers

  - Covers the balance cavity holding the coil-spring balance system inside the jamb

• 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.

• 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 45-degree angles.

• Bow Window

  - An angled combination of windows in 3-, 4- or 5-lite configurations. The windows are attached at 10-degree angles to project a more circular, arced appearance.

• Butyl

  - A rubber material that seals the glass to the spacer, creating an airtight and water-tight IG unit. Butyl has the lowest gas permeability of all rubbers.

• Cam Lock and Keeper

  - The mechanisms which pull the sash together when placed in the locked position.

• Casement Window

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

• Center of Glass U - and R-values

  - The U- and R-values measured from the center of the glass to 2-1/2" from the frame.

• 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.

• Convection

  - Heat transfer by currents that flow from a warm surface to a colder one.

• Dead-air space

  - The space between the panes of glass of an I.G. Unit.

• Desiccant

  - A material used in insulating glass to absorb water vapor which causes fogging.

• Double Hung Window

  - A window that has two operable sash which slide vertically.

• ENERGY STAR®

  - ENERGY STAR® is an independent government program establishing a standard set of guidelines to recognize the energy efficiency of various products. ENERGY STAR® guidelines are used in conjunction with a variety of building materials, including windows and patio doors. Over the past ten years, ENERGY STAR® guidelines have helped double the efficiency of windows they endorse.

• Fusion-welded

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

• Geometric

  - Specially designed windows classified as either Straight line Geometrics such as rectangles, triangles, trapezoid, octagons, pentagons, etc., or Radius Geometrics which include half-rounds, quarter-rounds, full-rounds, sectors, ellipses, eyebrows, etc.

• Glass

  - An inorganic transparent material composed of sand (silica), soda (sodium bicarbonate), and lime (calcium carbonate) with small quantities of alumina, boric or magnesia oxides.

• Glazing

  - The process of sealing the glass to the sash.

• Glazing Bead

  - A strip of vinyl which surrounds the edge of the glass and holds it in place in conjunction with other sealants.

• Grills/Grids

  - Decorative horizontal or vertical bars installed between the glass panes to create the appearance of the sash being dividing into smaller lites of glass.

• Head

  - The horizontal top portion of the main frame.

• Head Expander

  - A vinyl shape cut the width of a product and placed on the head, fitting over it snugly. This piece is used as a filler to expand or lengthen the unit from the head and take up the gap in the opening between the unit and the opening in the unit.

• I.G. Unit (Insulating Glass Unit)

  - Two or more lites of glass separated by a spacer and hermetically sealed at the glass edges.

• Intercept®

  Spacer System - Spacer system using a U-channel design to reduce the number of conduction paths.

• 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.

• Krypton Gas

  - An inert, odorless, colorless, tasteless, non-toxic gas which is about 12 times denser than air. It is used to replace air between the glass panes to reduce temperature transfer and deter convection. Used when a higher performance is desired than that produced with Argon gas.

• Lift Handle

  - A handhold for raising and lowering the sash. Handle implies that the handhold is not continuous across the sash.

• 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.

• Low E (Emissive) 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.

• Mullion

  - A vertical or horizontal connecting unit between two or more windows.

• Obscure Glass

  - Glass that has been made translucent instead of transparent.

• Patio Door

  - A glass door that slides open and closes on adjustable tandem rollers. Available in 2- or 3-lite configurations with the operable panel available in any position.

• Picture Window

  - A window that has no moveable sash.

• R-value

  - Resistance a material has to heat flow. The higher the R-value, the greater the resistance, the better the insulation. R-values are the reciprocal of U-values (R-value of 4 is equal to U-value of 0.25)

• Radiation

  - Wave energy transmitted directly from one object to another through the atmosphere or through transparent or translucent materials. The energy radiated is transmitted, absorbed, reflected or a combination of all three.

• Sash

  - The part of the window which contains the glass.

• Sill

  - The horizontal, bottom section of the main frame.

• Sill Extender

  - An extrusion that is attached to the bottom of the window to cover the gap between the sill and the rough opening.

• 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.

• Spacer

  - Material placed between two or more pieces of glass in order to maintain a uniform width between the glass, and prevent sealant distortion.

• Stile

  - The vertical sections of the sash.

• 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 shards.

• Tilt Latch

  - Mechanism that unlocks the sash and allows it to tilt in from the main frame.

• Total Unit U- and R-values

  - The U- and R-values of the window calculated from the average U and R-values from the center of glass, edge of glass, and frame.

• U-value

  - Amount of heat transferred through a material. The lower the U-value, the slower the rate of heat flow and the better the insulating quality. U-values are the reciprocal of R-values. (U-value of 0.25 is equal to R-value of 4)

• 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.

• Weather-stripping

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

• Weep Holes

  - Small openings designed to allow water to escape that might otherwise accumulate in a window's sill.