Frame, sash and glazing bead
The frame is fixed to the building; the sash is the moving or glazed element; the glazing bead secures the glass inside the profile.
Window dictionary: terms from A to Z
Window specifications use technical terms that are not always easy to understand. This dictionary explains the main concepts related to profiles, glazing, hardware, shutters, performance and installation.
217 terms
T
- Top-hung or bottom-hung sash
- A sash that pivots on a horizontal axis and opens partly at the top or bottom.
- Trickle vent
- A device that provides controlled airflow while the window remains closed.
- Thermal insulation
- The ability of the opening to limit heat transfer between both sides of the window.
- Track
- The rail or guide along which a sliding sash moves.
- Tilt-and-slide
- A system in which the sash can tilt and then move parallel to the frame.
- Tubular motor
- A motor installed inside the roller-shutter shaft.
- Tilt sash
- A sash that pivots on a horizontal axis and opens partially.
- Tilt-and-turn
- A window combining side-hung opening and top tilt operation with the same handle.
- Tilt-and-slide
- An opening in which the sash can tilt and move parallel to the frame.
- Top-hung projecting sash
- A sash hinged at the top and opening outwards at the bottom.
- Thermal bridge
- A zone where heat passes more easily because of a material or geometry change.
- Thermal break
- A low-conductivity separation between the inner and outer faces of a metal profile.
- Thermal transmittance
- The heat flow through an element per unit area and temperature difference.
- Transom
- A horizontal profile dividing an opening or joining parts of a window assembly.
- Triple glazing
- A sealed unit made from three panes and two cavities.
- Threshold
- The lower part of a door or pass-through window, important for accessibility, watertightness and drainage.
- Tilt-and-turn window
- A window combining side-hung and top-tilt opening.
- Toughened glass
- Thermally treated glass with increased strength and a characteristic fragmentation pattern.
G
- Glass energy absorption
- The part of solar radiation absorbed by the glass and converted into heat.
- Glazing
- The glass assembly installed in a window, whether monolithic, double, triple, laminated or coated.
- Glazing bar
- An element that divides the glass visually or physically into smaller panes.
- Glass bite
- The depth to which the edge of the glass is held inside the profile.
- Glazing block
- A block placed between glass and profile to support, centre and correctly transfer the glass weight.
- Glazing cavity
- The sealed space between two panes, containing dry air or an insulating gas.
- Glazing gasket
- An elastic gasket that maintains pressure and sealing between glass and profile.
- Glazing gasket
- A gasket that holds glass against the profile and limits water and air penetration.
- Glazing bead
- A removable profile that secures glass or a panel inside the frame or sash.
- Glass edge cover
- The depth of the glass edge retained inside the profile.
- Gasket compression
- The force with which the sash presses the gaskets against the frame.
- g-value
- Another name for the solar factor of glazing.
A
- Accessibility
- Conditions that make a window easier to use, including handle height, operating force and clear opening.
- Asymmetric glazing
- A glazing build-up with panes of different thicknesses, often used to improve sound insulation.
- Anchor
- A component that connects the window to the building substrate and transfers loads to the wall.
- Anodising
- An electrochemical treatment that gives aluminium a protective and decorative surface layer.
- Argon
- A gas placed in insulating-glass cavities to reduce heat transfer.
- Air-water-wind classification
- A combined reference to air permeability, watertightness and resistance to wind load.
- Active sash
- The sash opened first and normally fitted with the main handle.
- Air infiltration
- Uncontrolled air entering through joints, gaps or interfaces.
- Acoustic laminated glass
- Laminated glass with an interlayer designed to improve sound reduction.
- Air permeability
- The amount of air passing through a closed window under specified pressure differences.
- Architrave or trim
- A profile or moulding that visually covers the joint between window and wall.
F
- Finish
- Surface treatment that defines the colour, texture and part of the profile's protection.
- Friction stay
- Hardware that supports and controls the movement of a top-hung, tilt or projecting sash.
- Frame fraction
- The share of the total window area occupied by profiles rather than glass.
- Fixed light
- A glazed element that cannot be opened.
- Foil finish
- A decorative film applied to a profile, commonly used on PVC windows.
- Frame
- The fixed part of the window anchored to the opening.
- Finger pull
- A shallow or recessed grip used to move a sliding sash with the fingers.
- Frame fixing screw
- A screw intended to fix the frame directly to the substrate or subframe.
- French window
- A full-height window or glazed door providing access to a balcony, terrace or outside.
- Fixed window
- A window with no opening parts.
- Float glass
- Basic flat glass made by floating molten glass on a bath of tin.
- Frosted glass
- Glass whose surface or composition obscures direct vision and increases privacy.
S
- Sound insulation
- The ability of a window to reduce sound transmission between outside and inside.
- Swing sash
- A moving sash that pivots on hinges, often used as a general term for a casement sash.
- Setting block
- A load-bearing block that supports the glazing and transfers its weight to suitable points.
- Shutter head box
- A construction zone above the opening, commonly associated with housing a roller shutter.
- Sliding roller carriage
- The wheel or bearing mechanism that supports a sliding sash and allows it to move.
- Shutter belt
- A flexible belt used to raise and lower a roller shutter manually.
- Solar control
- The ability of glass or shading to limit energy from solar radiation.
- Sliding window
- A window whose sashes move horizontally or vertically along tracks.
- Solar factor
- The proportion of solar energy that ultimately enters through the glazing.
- Shutter hanger
- A flexible connector joining the first shutter slat to the shaft and transmitting movement.
- Sound frequency
- The number of wave oscillations per second, measured in hertz.
- Shutter guide
- The side profile along which the shutter slats move.
- Sash window
- A window whose sashes move vertically.
- Sash
- The moving or fixed element located inside the frame.
- Spacer bar
- The element that separates the panes and forms the perimeter of the insulating-glass cavity.
- Shootbolt gearbox
- Hardware on the passive sash that operates top and bottom bolts so the sash can open after the active sash.
- Structural opening size
- The available dimensions of the construction opening before the window is installed.
- Sealing membrane
- A flexible sheet used to control air, water or vapour movement at the installation joint.
- Sandwich panel
- A multi-layer panel, usually with an insulating core between two outer skins.
- Self-locking shutter
- A shutter designed to resist manual lifting of the curtain from outside.
- Subframe
- An element installed in the opening in advance to receive the window later.
- Shutter access panel
- The cover or opening that provides access to the inside of the roller-shutter box.
- Sealing
- The process of limiting air, water, vapour or sound passage through a joint.
- Sealant
- An elastic or plastic material used to fill and seal joints.
- Spacer bar
- The perimeter component that maintains the distance between panes in an insulating-glass unit.
- Structural silicone
- A sealant used in designed systems to bond glass and carry specified loads.
- Sliding system
- A profile family designed for sashes moving along tracks.
- Subframe
- An auxiliary frame fixed to the opening before the window is installed.
- Sliding window
- A window whose sashes move along tracks without swinging inward or outward.
- Solar-control glass
- Glass designed to limit part of the energy from solar radiation.
W
- Window sill
- The horizontal lower part of a window opening.
- Weatherstrip
- A flexible element that limits the passage of air, water, dust or noise.
- Window assembly
- The complete set of profiles, sashes, glass, gaskets, hardware and accessories closing an opening.
- Window pane division
- One of the visual or physical divisions forming a window.
- Watertightness
- A window's ability to prevent rain penetration under the relevant test conditions.
- Window hardware
- The set of components that opens, closes, locks, guides or adjusts a window.
- Warm edge
- A term for low-conductivity spacers at the perimeter of insulating glazing.
R
- Reinforcement core
- An internal element that increases the stiffness or fixing capacity of a profile.
- Roller-shutter box
- The enclosure above a window in which the shutter curtain rolls up.
- Roller-shutter shaft
- The tube inside the box around which the shutter curtain rolls.
- Rebate
- A recess in the profile that receives glass, a gasket, a panel or part of the sash.
- Relative humidity
- The ratio between water vapour in the air and the maximum amount it could hold at the same temperature.
- Replacement installation
- Installing a new window in an existing building while retaining or removing the previous frame.
- Roller-shutter slat
- One of the articulated horizontal pieces forming a roller-shutter curtain.
- Rooflight
- A glazed opening in a roof or high area that provides daylight and sometimes ventilation.
- Roller shutter
- A curtain of articulated slats that rolls around a shaft inside a box.
- RAL colour system
- A standard colour-reference system widely used for profile finishes.
- Reinforcement
- An added element that increases stiffness, strength or fixing capacity.
- Resistance to wind load
- The ability of a window to withstand pressure and suction without unacceptable deformation.
- Rw
- The weighted sound-reduction index used to describe acoustic insulation.
- Reflective glass
- Glass that reflects part of visible radiation and changes the façade appearance.
P
- Parapet
- The part of the wall between the floor and the bottom of a window, or a protective element in front of a low opening.
- Plumb alignment
- The check that the frame has been installed correctly in the vertical plane.
- Pressure-equalisation chamber
- A profile zone designed to balance pressure and direct water towards the drainage outlets.
- Profile chamber
- An internal compartment created by the geometry of a profile.
- Psi value, Ψ
- The linear thermal-transmittance value of a junction such as the glass edge or installation perimeter.
- Polyurethane foam
- An expanding material used to fill and insulate part of the installation joint; it does not replace mechanical fixings.
- Protective film
- A temporary film that protects the profile finish during manufacture, transport and installation.
- Passive sash
- The secondary sash of a two-sash window, opened after releasing its own locking mechanism.
- Perimeter clearance
- The planned gap between window and opening for fitting, levelling, sealing and movement.
- Profile moment of inertia
- A geometric property related to a profile's resistance to bending and deformation.
- Powder coating
- A paint finish applied to a profile and normally cured in an oven.
- Pull handle
- A larger grip commonly used on doors, sliding systems and large glazed openings.
- Profile junction
- A connection between profiles forming a corner, division, joint or change of plane.
- Profile
- A longitudinal component with a defined cross-section used for frames, sashes, mullions or accessories.
- Pivot hinge
- A rotating hardware component similar to a hinge, used on doors and windows.
- Polyamide thermal strip
- A low-conductivity material joining the inner and outer aluminium profile sections in a thermally broken system.
- PVB
- Polyvinyl butyral, widely used as an interlayer in laminated glass.
- Pivot point
- A traditional term for the point or fitting on which a sash or door turns.
- Pull
- A component used to push or slide a sash without necessarily operating a lock.
C
- Casement opening
- A side-hung opening in which the sash pivots on vertical hinges.
- Concealed hinge
- A hinge integrated into the profile and hidden when the window is closed.
- Central lock
- A locking mechanism located at the meeting point of two sashes or in the centre of a slider.
- Condensation
- Water formed when moisture in the air meets a surface cold enough to reach the dew point.
- Concealed drainage
- A water-evacuation system whose outlets are hidden within the profile geometry.
- Corner cleat or squareness
- A part joining profiles at a corner, or the check that a frame forms right angles.
- Cavity gas
- Gas introduced into an insulating-glass unit to modify its thermal performance.
- Concealed sash
- A design in which part of the sash profile is hidden behind the frame from the outside.
- Centre gasket
- A gasket located between frame and sash in the middle zone of certain casement systems.
- Clear opening
- The unobstructed space available to pass through an open door or window.
- CE marking
- Identification accompanying products covered by European requirements and a declaration of performance.
- Curtain wall
- A lightweight façade system that encloses the building without normally carrying the main structural loads.
- Compensating profile
- An auxiliary profile used to adjust dimensions, absorb differences or complete a junction.
- Casement system
- A profile family designed for hinged sashes.
- Cross ventilation
- Air renewal created by openings on different sides of a home.
- Ceramic-frit glass
- Glass with enamel patterns or opaque areas applied by screen printing and heat treatment.
H
- Hinge
- A hardware component that joins the sash to the frame and allows it to pivot.
- Hardware groove
- The groove in a profile that receives the hardware components.
- Handle
- The component used to operate the opening and locking mechanism.
- Hardware adjustment
- Adjustment of hinges, rollers, locks or stays to correct sash position and operation.
- Hold-open device
- A device that holds a sash in a selected position or limits its movement.
- Heat tempering
- A glass treatment that increases strength and changes the breakage pattern.
- Heat-strengthened glass
- Thermally treated glass stronger than annealed glass but different from fully tempered glass.
L
- Locking pin
- A moving hardware pin that engages with a keep to lock the sash.
- Louvre screen
- An assembly of slats or separated pieces used to regulate light, airflow or privacy.
- Lift-and-slide
- A system that slightly lifts the sash when the handle is operated, releasing the seals and easing movement.
- Lintel
- The horizontal upper part of a window opening.
- Low-iron glass
- Glass with reduced iron content, greater transparency and less green tint.
- Low-E
- The common English term for low-emissivity glass.
- Lockable handle
- A handle that can be locked to prevent or limit operation.
- Levelling
- Adjustment that places the frame or threshold at the intended horizontal level.
- Light or panel
- One of the surfaces or divisions making up a glazed assembly.
- Latch
- A moving part that engages a keep to hold a sash closed.
- Locking point
- The location where a locking pin, latch or other hardware secures the sash.
- Low-emissivity glass
- Glass with a coating that reduces radiant heat transfer.
- Low-iron glass
- Glass with greater colour neutrality and light transmission than conventional float glass.
- Laminated glass
- Glass made from two or more panes bonded with one or more interlayers.
M
- Mushroom cam
- A widened locking cam that engages a matching keep and helps resist levering.
- Multipoint lock
- Hardware that locks the sash at several points with one operation.
- Minimal sliding system
- A sliding system designed to reduce visible profile width and maximise glazed area.
- Meeting stile
- The area where two sashes of a window or sliding system meet.
- Mishandling position
- A condition in which the handle is operated incorrectly and the sash is held by only part of the hardware.
- Mechanical fixing
- A connection using screws, anchors or straps capable of transferring loads to the substrate.
- Mass-spring-mass principle
- An acoustic principle involving two masses separated by a resilient cavity.
- Micro-ventilation
- A hardware position that leaves a very small gap between sash and frame.
- Mullion
- A vertical profile dividing an opening or joining separate lights.
- Molecular sieve
- Desiccant material inside the spacer that absorbs residual moisture from the glass cavity.
- Misting
- Condensation made of fine droplets that reduces surface transparency.
- Mechanical ventilation
- Air renewal provided by fans, ducts and extract or supply terminals.
- Monolithic glass
- A single pane with no cavity or laminated interlayer.
E
- Euro groove
- A standard groove geometry used in many aluminium systems for compatible hardware.
- Expanding tape
- A compressed sealing material that expands after installation to fill a joint.
- End cap
- A part that closes, finishes or supports the end of a profile, shaft or guide.
- Espagnolette
- A handle-operated mechanism that moves several locking points along the sash.
- Energy demand
- The calculated energy needed to maintain specified indoor comfort conditions.
- Energy efficiency
- The relationship between the comfort achieved and the energy required to provide it.
- Emissivity
- A surface's ability to emit thermal energy as radiation.
- Extrusion
- A manufacturing process in which material is pushed through a die to create a constant-section profile.
- Espagnolette bolt
- A locking mechanism that moves rods or bolts towards the top and bottom of a sash.
- Extruded shutter slat
- A slat made by extrusion, generally stiffer than a roll-formed slat of similar size.
- External seal
- The protection of the installation joint against rain, sunlight and external exposure.
- External sill or flashing
- The lower exterior component that directs water away from the façade.
O
- Outer frame
- The fixed window element attached to the opening; often used as another term for frame.
- Out-of-square condition
- A geometric irregularity where a frame or opening does not form right angles.
- Opening restrictor
- A device that limits the maximum angle or distance a sash can open.
- Orientation
- The compass direction faced by a window, relevant to sun, wind and glazing selection.
- Overlap
- The part of one profile that partly covers another element or junction.
K
- Keep
- The frame-mounted part into which a locking pin, latch or bolt engages.
- Krypton
- A gas used in the cavities of some high-performance insulating-glass units.
- Kick panel
- The opaque or reinforced lower section of a door, French window or glazed enclosure.
D
- Decibel, dB
- The unit used to express sound levels and differences in acoustic insulation.
- Drain outlet
- An opening that discharges water collected inside the profile to the exterior.
- Double glazing
- A sealed unit made from two panes separated by a cavity.
- Drip groove
- A projection or groove that stops water travelling along the underside of a component towards the building.
- Dew point
- The temperature at which water vapour in the air can begin to condense.
- Drainage zone
- The internal profile area that collects water and directs it to the exterior outlets.
B
- Backer rod
- A flexible cord that controls sealant depth and prevents adhesion to the bottom of a joint.
- Belt guide
- The component through which the roller-shutter belt passes through the box or wall.
- Belt winder
- The indoor mechanism that retracts and stores a roller-shutter belt.
I
- Ionomer interlayer
- A high-performance interlayer used in certain laminated-glass constructions.
- Isotherm
- A line joining points at the same temperature in a thermal detail or calculation.
- Installation joint
- The perimeter interface between the window and the wall.
- Insect screen
- A mesh that limits insect entry and must not be treated as fall protection.
- Internal seal
- The installation-joint layer mainly intended to control air movement from inside.
- Internal surface temperature
- The temperature reached by the indoor face of glass, profile or wall.
- Insulating glass unit
- Two or more panes separated by sealed cavities.
J
- Jamb
- Either vertical side of a window opening.
- Joint or gasket
- A flexible element or designed gap used to seal, accommodate movement or separate components.
N
- Neutral-cure silicone
- A neutral-curing sealant compatible with many window and glass materials.
V
- Visible light transmittance
- The proportion of visible light passing through glass.
U
X
- XPS
- Extruded polystyrene used as thermal insulation in some junctions and shutter boxes.
No terms found.
Terms worth distinguishing
Espagnolette, shootbolt and passive-sash gearbox
An espagnolette operates several locking points, shootbolts move into the top and bottom, and the passive-sash gearbox releases the secondary sash.
Uf, Ug and Uw
Uf describes the profile, Ug the glazing and Uw the complete window. Uw is normally the most useful value for comparing equivalent windows.
Laminated and toughened glass
Laminated glass retains many fragments after breakage; toughened glass breaks into small pieces. They serve different safety functions.
Shutter, box and access panel
The shutter is the moving slat curtain, the box houses the roll, and the access panel opens the box for maintenance.
Subframe and trim
The subframe receives and helps fix the window; the trim only covers the joint visually and does not replace sealing.
Frequently asked questions about window terms
What is a passive-sash gearbox?
It is the hardware that releases the secondary sash of a two-sash window, usually operating top and bottom shootbolts.
What is a glazing bead?
It is the removable profile that secures the glass inside the sash or frame.
What is the difference between Ug and Uw?
Ug applies to the glazing, while Uw describes the complete window including frame, glass edge and dimensions.
What does thermal break mean?
It is a low-conductivity separation between the inner and outer parts of a metal profile.
Can foam fix a window?
Foam can fill and insulate part of the joint, but structural stability requires suitable mechanical fixings.