A to Z: Window & Door Terminology

Have you ever been confused when talking to a window and door contractor? Window and door terms can be confusing to average homeowners, so we hope this page is a good resource!

Aluminum Windows: type of window where the frame and sash are made out of aluminum. Besides their superior strength, one of the few windows great for noise reduction. Read more here.

Aluminum-Clad Window: A window with wood construction covered with aluminum sheet having a factory-applied finish (to provide a longer maintenance-free life)

Awning Window: A top-hinged sash.

Arch window: 4 sided unit with a curve at the top

Argon gas: Colourless, odourless gas used in the air space of double pane Low-E glass to increase the insulating performance.

Anti-Bandit Glass (smash and grab resistance): Anti-Bandit Glass is a laminated glass made up of two annealed glass sheets bonded together by 1.5mm thick plastic interlayer, and is tested to BS 5544. It is a security glass designed to resist manual attack and to delay access to a protected space for a short period of time. The increased effort and time required to develop an opening in the laminate serves to dissuade and thwart would-be intruders or burglars. It is ideal in situations where the noise generated by the attack alerts neighbours or inhabitants.

Bay Window: Windows that project out from the wall and extend to the ground. An Angle Bay Window refers to the angle departure from the plane of the wall. Window consisting of three or more units that angle out beyond the wall; often configured with a large center unit and two flanking units. Bay View Window detail

Bullet Resistant: SUPER-SAFELITE BR (Bullet Resistant) glass is a laminated glass made in a multi-laminate process, which laminates various thicknesses of glass to meet various weapons ballistics tests. Bullet Resistant glass is ideal for windows in security areas of banks or cash handling offices. Bullet resistant laminated glass can be supplied with either a PVB or CIP interlayer.
Q- Windows manufactures a range of bullet resistant laminates suitable for a variety of weapon classes. The make-ups are classified into AS/NZS 2343, BS 5051 and German Standard DIN 5229 classes of resistance.

Blast Resistant: SUPER-SAFELITE EBR (Explosive Blast Resistant) glass is capable of withstanding the blast impact from explosives and can be designed and manufactured to suit each individual project. The glass is normally a multi-laminate, the thickness of which is determined by the required blast resistance. EBR glass, when glazed, is visually similar to ordinary glass. It is designed to protect against terrorist attack or explosive forces from industrial accidents.

Casement Window A window sash which swings open on side hinges.

Celsius: A centigrade scale of temperature measurement based on 0° as the freezing point and 100° as the boiling point of water. Abbreviated °C.

Coated Glass: A window glass with an outside surface provided with a mirror reflective surface; the shading coefficient ranges from 20% to 45%. See Shading Coefficient.

Commercial Standard: A voluntary set of rules and regulations covering quality of product (or installation), method of testing, rating of the product, certification, and labeling of manufactured products.

Condensation: The deposit of water vapor from the air on any cold surface whose temperature is below the dew point, such as a window glass or frame that is exposed to cold outdoor air. See Dew Point Temperature.

Coolness Factor (CF): The Coolness Factor (or luminous efficacy) is the visible light transmission divided by the shading coefficient. CF = VLT / SC. It is a useful means of comparing different glass types in terms of the trade-off between light transmission and heat control in selecting glass. Glass types with a coolness factor of 1 transmit as much light as heat, those with a coolness factor lower than 1 transmit more heat than light and those with a coolness factor greater than 1 transmit more light than heat.

Drip cap: horizontal molding used to divert water from the top casing so that it drips beyond the outside of the frame; this can prevent water damage

Desiccant: A drying agent, such as silica gel, used by some manufacturers between the panes of insulating glass to prevent fogging between the panes.

Double-Casement Window: Window with two vertically moving sashes, each closing a different part of the window.

Double Glazing Windows: Windows, such as a regular window equipped with insulating glass unit made of minimum two layers of glass with air space between panes.

Double Window: Two windows separated by a mullion, forming a unit. Also called a coupled window.

Electric operator: A motorized device that provides for remote operation of an awning window

Extruded aluminum: Aluminum that is shaped by running it through a dye, typically more durable than roll-formed material

EPDM (Ethylene Propylene Diene Monomer): A synthetic rubber. The main properties of EPDM are its outstanding heat, ozone and weather resistance. The resistance to polar substances and steam are also good. It has excellent electrical insulating properties. It has good resistance to ketones, ordinary diluted acids and alkalines.

Fenestration: Refers to an opening in a structure such as windows, doors and skylights. Can also refer to the placement of windows and doors in a building

Fixed Window: Window which is non-operative (does not open).

Float Glass: Smooth glass formed on the top of molten tin surface; a flat glass sheet.

French Casement Window: Two casement sashes, each hinged on one stile and opening in the middle with no center mull but with a half lap connection. This allows a smaller rough opening to make egress since there is a large unobstructed opening.

Friction Hinge: A window hinge which remains open in any position by means of friction in the hinge.

Frame depth: width of the window frame from the inside to the outside

Glazing: The glass panes or lights in the sash of a window. Also the act of installing lights of glass in a window sash.

Glazing Bead: A removable trim that holds the glass in place.

Glazing Channel: A groove cut into the sash for the mounting of glass.

Handing: Opening direction of hinging windows and doors; direction is determined by location of hinge on unit.

Heat-Absorbing Glass (Tinted Glass): Window glass containing chemicals (with gray, bronze, or blue-green tint) which absorb light and heat radiation, and reduce glare and brightness. Shading coefficient of this glass varies from about 50% to 70%.

Hinge: A movable joint enabling a window to swing open.

Heat Gain: Heat from solar radiation that enters a building.

Inactive panel / sash: Panel / sash that will open only after active panel / sash is opened

Insulating Glass: Double- or triple-glazing with an enclosed, dehydrated, and hermetically sealed air space between the panes; the space is commonly from 6 mm to 12 mm.

Laminated Glass: is a type of safety glass that holds together when shattered. In the event of breaking, it is held in place by an interlayer, typically of polyvinyl butyral (PVB), between its two or more layers of glass. The interlayer keeps the layers of glass bonded even when broken, and its high strength prevents the glass from breaking up into large sharp pieces. The PVB interlayer also gives the glass a much higher sound insulation rating, due to the damping effect, and also blocks 99% of incoming UV radiation.

Latch: A device which holds a window shut, such as the latch at the meeting rail of a double-hung window or one mounted on the stile of casement windows, often referred to as a lock.

Lock: A fastening device in which a bolt is secured and can be operated by a key.

Low-Emissivity Coating (Low-E): Coating for glass surfaces which reflects radiant heat energy rather than allowing that energy to radiate through the glass surface. The lower the emissivity of the glass the lower the heat transfer coefficient.

Mullion: Vertical member between window units.

Multi-point lock: Lock that engages the sash or panel in multiple locations; activated by a single motion

Orientation: placement of windows in regard to access, view, sun, etc.

Outdoor/Indoor Transmission Class (OITC): Measurement standard used to indicate the rate of sound transmission between indoors and outdoors (see also STC)

Obscure/Translucent Glass: A frosted or textured glass that transmits light, but obscures the view.

PVC: a molded plastic material used for window frames.

Protection against Vandalism: Damage caused by vandalism can be minimised by the use of laminated glass, which ensures that any broken shards of glass adhere to the interlayer and acts as a deterrent to burglars by slowing them down and attracting attention. The amount of protection is dependent on the glass and interlayer type and thickness. Standard 6.38mm laminated glass will provide minimum protection and 10.38mm will provide greater protection.

Perceived Sound Reduction (PSR): The percentage by which the human ear detects a lessening in sound pressure or noise is known as the Perceived Sound Reduction. A 10dB reduction in sound pressure level is generally perceived as a halving of the original noise. Sound reduction values are ‘weighted’ and used to calculate the perceived sound reduction as a ratio relative to the Rw for 3mm clear float.
The dB difference in the Rw value for a glass type when compared to 3mm float is calculated as a perceived sound reduction percentage.

Reflective glass: type of glass that reflects the sun’s rays

Replacement Window: A window designed to replace and fit into an existing window opening once the old window is removed

R-value: measure of resistance to heat flow; the higher the value, the better the heat insulating properties

Sash: A framework that holds the panes of a window in the window frame

Sealant: A compressible PDM material used to seal any opening or junction of two parts, such as between the glass and a metal sash.

Shading Coefficient: The ratio of the total solar heat gain through a particular glass compared to the total solar heat gain through 3mm clear float glass. (86%) The shading coefficient of 3mm clear float is by definition 1.0 and represents a base glass performance. The lower the shading coefficient the less heat gain and thus more shading is provided by the glass. The shading coefficient is calculated as SC = SHGC / 0.86.

Silicone: An enduring sealing agent that resists water.

Sliding Window: A window which moves horizontally in grooves or tracks.

Sliding Door: A door which moves horizontally in grooves or tracks.

Single Glazing: Use of a single pane of glass in a window. Not usable for sound proof windows.

Solar Heat Gain Coefficient (SHGC): The measure of the total solar energy transmittance entering a building through the glazing as heat gain. It is the total heat transmission of direct solar transmission and that proportion of absorbed radiation that is re-radiated into the building from the action of heat absorbing glass. The lower the SHGC the better the glass restricts heat energy transmission. The SHGC is also known as the Solar Factor (SF).

Sound Transmission Class (STC): Rating system used to measure how much sound is transferred through windows/doors (see also OITC)

Sound Transmission Loss (STL): The average Sound Transmission Loss is useful for determining the effectiveness of glazed panels to isolate exterior noise (such as traffic) from a building. It is derived from the average of the measured transmission loss at eighteen 1/3 octave frequency bands between 100Hz and 5000Hz, or 16 bands from 125 to 4000Hz. The average STL is measured in decibels (dB), the higher the average STL figure, the more effective the glazing will be in reducing sound transmission.

Tempered Glass: Special heat-treated, high-strength safety glass which shatters into pebble-sized particles but not into slivers.

Thermal Barrier: (Thermal Break) - A material of high thermal resistance placed between two metal sash, or installed between adjoining metal framing of metal windows, in order to reduce thermal conduction from indoors to outdoors.

Thermal Conduction: Heat transfer through a material by contact of one molecule to the next. Heat flows from a high temperature area to one of lower temperature.

Thermal Conductivity: Heat transfer property of materials expressed in units of 'Btu per hour per inch of thickness per square foot of surface per one degree F. temperature difference.' Referred to by the letter 'k.'

Thermal Conductance: Same as Thermal Conductivity except thickness is 'as stated' rather than one inch. Referred to by the letter 'C.'

Thermal Insulation: A material that resists heat flow. Material having a high R-value.

Thermal Resistance (R-value): A property of a substance or construction which retards the flow of heat; one measure of this property is R-value. See Heat Transfer Coefficient.

Tilt Window: A window designed in such a way that the sashes tilt inward for easy cleaning of the outside glass surface.

Tinted Glass: See Heat-Absorbing Glass.

Transom (Transom Bar): A horizontal member separating a door from a window panel above the door, or separating one window above another.

Transom Light (Transom Window): The window sash located above a door.

U-value: The U Value is the measure of air to air heat transfer through glass due to the thermal conductance of the glazing and the difference between indoor and outdoor temperatures. It is expressed as W/m2K (Watts per m2 per 1° Kelvin) or W/ m2 °C (1 Kelvin equals 1°C). The U value is a measure of the rate of heat gain or heat loss through the glazing due to environmental differences between outdoor and indoor air. It is measured at the centre of the glass (cog).The lower the U Value the lower the heat transfer, the better the insulation.

uPVC Windows: type of window where the frame and sash are created out of uPVC.

Visible Light Transmission (VLT): The percentage of visible light that is transmitted through the glass. The VLT is measured in the 380-780nm wavelength range perpendicular to the surface. The higher the percentage the more daylight.

Visible Light Reflection (VLR): The percentage of visible light that is reflected by the glass surface, measured in the 380-780nm wavelength range perpendicular to the surface. The VLR can be given as the reflection from the external surface 1 or internal surface 2. The higher the percentage the more reflection.

Window: A glazed opening in an external wall; an entire unit consisting of a frame, sash and glazing, and any operable elements.

Window Frame: The fixed frame of a window, which holds the sash or casement as well as hardware.

Window Hardware: Various devices and mechanisms for the window including: fasteners and locks, hinges and pivots, lifts and pulls and pulleys.

Window Unit: A complete window with sash and frame.

Wind Pressure: The pressure produced by stopping the wind velocity; the main cause of air infiltration.

Wind Load: Force extended on a surface by moving air.

Weighted Sound Reduction Index (RW): The Weighted Sound Reduction Index incorporates frequency modified correction for the human ear’s response. The Rw is reported in dB and is a composite rating of sound reduction at frequencies from 100 - 5000Hz. Numerically, it is comparable to the STC values but the numbers are in dBA.