Casement Window glossary of terms & specifications
15 technical terms, material grades and Irish standards explained in plain English so you know exactly what is on a written quote.
Sorted A to Z for quick reference when comparing specifications.
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Key casement window terms explained
Airtightness Tape & Low-Expansion Foam
Flexible polyurethane acoustic/thermal foam injected into the 5mm–10mm perimeter fitting gap around the new window frame, sealed internally with vapour-control tape before plastering.
Dummy Transom / Equal Sightlines
A fixed dummy sash fitted into non-opening panes so the glass area and frame border match the adjacent opening casements identically from the street.
Easy-Clean 90° Friction Stay Hinge
A stainless steel side-hung hinge that opens normally for ventilation and slides across on a release catch so you can clean the outside glass safely from inside an upstairs room.
Egress Friction Hinge (Part B Fire Escape)
An unobstructed side-hung hinge that swings the casement sash clear to a full 90° opening angle to meet Irish Building Regulations Part B in every bedroom.
Espagnolette Multi-Point Locking
A steel gearing mechanism along the closing edge of a casement sash that drives mushroom-headed cams and shootbolts into steel keeps when you turn the key-locking handle.
Flush Casement (Flush Sash)
A heritage-style casement window where the opening sash closes completely flush into the outer frame faceplate like traditional 19th-century joinery, rather than overlapping it.
Internal Glazing Bead
The clip-in beading that holds the sealed glass unit fitted on the room side of the window so nobody can remove the glass from outside.
Mechanical Timber-Look Corner Joint
A square-butted corner joint (such as Timberweld) used on woodgrain flush casements in place of a diagonal 45° plastic weld.
Multi-Chamber uPVC Profile (70mm–82mm)
Extruded unplasticised PVC frame divided into 5 to 7 internal insulating air chambers reinforced with galvanised steel sections.
Night-Vent Lock Position
A secondary slot in the window striker plate that lets you lock the casement handle with a 5mm–8mm ventilation gap that cannot be levered open from outside.
Part B Fire Escape Minimum Clear Opening
Irish Building Regulations rule requiring every habitable upstairs room to have an opening light of at least 0.33 m² clear area, at least 450mm high × 450mm wide, with the bottom cill 800mm–1,100mm above the floor.
Stormproof (Lipped) Casement
The standard Irish casement profile where the opening sash overlaps the outer frame face with dual perimeter weather seals for maximum resistance to driving rain.
Top-Hung Fanlight
A small horizontal casement sash at the top of a window bay that opens outward from the bottom so you can ventilate the room in rainy weather without water blowing in.
Warm-Edge Spacer Bar
An insulating composite or stainless-polymer bar separating the two or three panes of glass around the perimeter of a sealed unit to stop condensation along the bottom glass edge.
Whole-Window U-Value (Uw)
The overall heat-loss rating in W/m²K combining both the frame and glass; Irish Part L requires ≤ 1.4 W/m²K for replacement windows, while triple-glazed casements reach 0.8–1.1 W/m²K.
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Questions homeowners ask
How much do casement windows cost in Ireland supplied and fitted?
A white A-rated double-glazed uPVC casement window costs €350 to €850 supplied and fitted. Colour-foiled or triple-glazed (0.8 W/m²K) uPVC casements cost €550 to €1,100, flush sash casements cost €750 to €1,300, thermally broken aluminium casements cost €700 to €1,550, and timber-alu-clad casements cost €1,100 to €1,950 per window.
How much does it cost to replace all casement windows in a 3-bed semi?
For a typical Irish 3-bed semi-detached house (8 to 10 casement windows), full replacement costs €4,500 to €8,800 in white uPVC, €6,800 to €11,500 in flush sash casements, or €9,000 to €15,500 in thermally broken aluminium. If the home qualifies for the €3,000 SEAI Windows Grant, subtract €3,000 from those totals.
What is a casement window?
A casement window is a window whose opening sash is attached to the outer frame by side-mounted or top-mounted friction hinges (stays) and swings outwards when you turn the handle. It is the most weather-tight and popular window style in Ireland because wind blowing against the glass presses the sash tighter onto its twin compression gaskets.
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