Glossary

Northwest Energy Savers: Glossary of Terms

It is helpful to be able to understand the “terms of the trade.” The glossary of terms that follows provides some of the common terms associated with replacement windows that you may encounter when reviewing companies and products.

ABCDEFGHIJKLMNOPQRSTUVWXYZ

A

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.

Air Latch

Latch mechanism on the interior face of the sash that retains the window in a partially open position for ventilation.

Argon Gas

An odorless, colorless, tasteless, nontoxic gas which is six times denser 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.

B

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 watertight IG unit. Butyl has the lowest gas permeability of all rubbers.

C

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.

D

Dead-air space

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

Deadlite

A piece of glass or IGU with a sash profile around it; not set within the main frame of a window 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.

Double-strength Glass

Glass with a thickness of approximately 1/8″.

Dry glazing

An alternative method of placing glass in a door or window. No glazing mastic is used. Dry glazing is recommended whenever reflective coatings are glazed to first surface. E

Egress Code

The code that requires a minimum opening of a window for persons to exit or firefighters to enter a building.

ENERGY STAR

ENERGY STAR is an independent U.S. 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.

Extruded screen frame

Different from a Roll formed frame, this frame is pressed through a form or die.

F

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.

G

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.

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

H

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.

Hook accessory

Accessories that snap to the hook frame and provide easy installation.

Hopper

A window with a bottom-hinged sash that opens inward for ventilation.

I

I.G. Unit (Insulating Glass Unit)

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

J

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.

K

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, nontoxic 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.

L

Laminated Glass

Two or more pieces of glass bonded together over a plastic interlayer.

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.

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.

M

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 is closed.

Meeting Stile

The vertical section of a pair of sash that meets when the sash is closed.

Mesh

Fabric made of either fiberglass or aluminum, used in the making of screens.

Mullion

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

N

Nailing Fin

An extrusion attached to the main frame of a window used to secure the unit to the rough opening.

O

Obscure Glass

Glass that has been made translucent instead of transparent.

Oriel

A window with the meeting rail located off center of the frame. Most oriels have a 60/40 configuration.

Overlapping and Interlocking Meeting Rail

A meeting rail which overlaps and interlocks both sash.

P

Patio door

A glass door that slides opens and close on adjustable tandem rollers. Available in 2, 3 or 4-lite configurations with the operable panel available in any position.

Picture Window

A window that has no moveable sash.

Pivot Alignment System

A 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.

Pull Handle

A handhold for sliding the sash back and forth. Handle implies that the handhold is not continuous across the sash.

Pull rail

A handhold for sliding the sash back and forth. Rail implies that the handhold is continuous across the sash.

Pull Stile

A handhold for sliding the sash back and forth. Stile implies that the handhold is continuous across the sash.

R

R-value

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

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.

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.

Roll formed 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.

S

Sash

The part of the window which contains the glass.

Sash 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.

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 gains.

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.

Single Hung

A window in which one sash slides vertically and the other sash is fixed.

Single strength Glass

Glass with a thickness of approximately 3/32″.

Slider Window

A window in which the sash moves horizontally. Sliders are available in a 2-lite or 3-lite configuration, with the 3-lite having operable end vents. Also referred to as xo or xox.

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

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

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

Stepped Sill

A triple-stepped, sloped sill design.

Stile

The vertical sections of the sash.

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.

T

Tape Glazing

Two-sided tape used to secure and seal the glass to 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.

Tilt-in/lift-out sash

A sash that can be tilted to the interior and removed for cleaning and is manufactured by welding.

Total Unit U- and R-values

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

U

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.

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 window.

V

Vent-lock

Latch mechanism on the interior face of the sash which retains the window in a partially open position for ventilation.

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.

W

Weather-stripping

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

Weep flaps

A weep hole that is covered with vinyl flap that allows water to escape, while keeping insects out.

Weep Holes

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

Weep Slots

Slots or holes in the sill (bottom) member of the sash frame that provides an outdoor release of infiltrated rainwater.

Wet Glazing

A silicone-based substance used to secure and seal the glass to the sash.

Wood blocks

Pieces of plywood that come in different thickness, depending on the depth of the hook of the frame. They are used to make the window flush with the opening it is filling. They are also used to assist in pre-mulling windows together and give the screw more to bite into when joining the windows.