Window Replacement 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.
Free, no obligation. One vetted installer covering your county replies, not five.
Key window replacement terms explained
0.8 W/m²K Triple Glazing
A three-pane 40mm–44mm sealed glass unit with two low-E heat-reflecting coatings, argon gas and warm-edge spacer bars that cuts window heat loss by up to 70% compared with 1990s double glazing.
Airtightness Tape & Low-Expansion Foam
Sealing the 5mm–10mm perimeter fitting joint around a replacement window frame with flexible polyurethane foam and internal vapour-control tape so warm room air never leaks into the cavity.
Aluclad (Timber-Aluminium) Frame
Engineered Nordic pine or European oak on the inside of the room protected externally by a maintenance-free powder-coated aluminium rain-screen.
Composite Front Door (PAS 24)
A 48mm–70mm solid-core or high-density foam-filled GRP/timber entrance door with multi-point hook locks and triple-glazed sidelights.
Egress Friction Stay (Part B Fire Escape)
A side-hung stainless steel hinge that opens a bedroom window to a full 90° clear escape opening (minimum 0.33 m², 450mm × 450mm) to satisfy Irish Building Regulations Part B.
Espagnolette Multi-Point Locking
Mushroom-headed steel locking cams and shootbolts driven around the sash perimeter when the key-locking window handle is closed.
Flush Sash Casement
A heritage-style replacement window where the opening sash closes completely flush into the outer frame faceplate like traditional timber joinery.
Heat Loss Indicator (HLI ≤ 2.3)
The whole-house thermal benchmark on an SEAI BER assessment required for a home to qualify for the SEAI Windows and Doors grant.
Internal Glazing Bead
Clip-in beading fitted on the room side of the window sash so the sealed glass unit can never be removed from outside.
Part F Trickle Ventilation
Concealed slot ventilators in the window head frame that provide continuous background fresh air in homes without Mechanical Ventilation with Heat Recovery (MVHR).
Part L Maximum U-Value (Uw ≤ 1.4 W/m²K)
The Irish Building Regulations thermal standard for replacement domestic windows (≤ 1.4 W/m²K for windows and ≤ 1.6 W/m²K for external doors).
SEAI Windows & Doors Grant (€1,500–€4,000)
Grant support for pre-2011 Irish homes upgrading to whole-window Uw ≤ 1.4 W/m²K as part of a One-Stop-Shop or Heat-Loss-Ready package (__€1,500 apartment, €3,000 mid-terrace, €3,500 semi-detached, €4,000 detached, plus €800 per door__).
Spring-Balanced Sliding Sash Window
Vertically sliding Georgian or Victorian replacement windows operating on concealed tensioned spiral balances with tilt-in cleaning latches and draught-proof brush seals.
Warm-Edge Spacer Bar
An insulating composite perimeter bar between the glass panes that eliminates cold bridging and morning condensation around the edge of the glass.
Whole-Window U-Value (Uw)
The true heat-loss figure in W/m²K combining the frame profile, spacer bar and centre-pane glass (Ug) as a complete installed unit.
Real examples and installation detail
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Questions homeowners ask
How much does it cost to replace all windows in a 3-bed semi-detached house in Ireland?
Supplying and fitting 8 to 10 A-rated uPVC windows in a typical 3-bed semi-detached house in Ireland costs €4,500 to €7,800 in smooth white, €5,400 to €9,200 in dual-colour foiled uPVC (such as Anthracite Grey outside and white inside), or €10,500 to €16,800 in triple-glazed Scandinavian aluclad, including removal of old frames, reveal plastering and 13.5% VAT.
Is triple glazing worth the extra cost over double glazing in Ireland?
Yes. Upgrading a full house from A-rated double glazing (1.2 W/m²K) to 40mm–44mm argon triple glazing (0.8 W/m²K) typically adds just 12% to 15% (€600 to €1,100 on a 3-bed semi-detached house), raises internal glass surface temperature to ~18.4°C in winter, stops morning condensation and cuts street noise.
Can I get the SEAI grant for replacing my windows and doors?
Under SEAI rules, the Windows Grant (€1,500 apartment, €3,000 mid-terrace, €3,500 semi-detached, €4,000 detached) and Doors Grant (€800 per door for up to 2 doors) are available for pre-2011 homes achieving Uw ≤ 1.4 W/m²K as part of a whole-house upgrade reaching at least a B2 BER and Heat Loss Indicator (HLI) ≤ 2.0. If your home only needs windows and doors, booking directly with an independent installer often costs less out of pocket than a One Stop Shop package.
Window replacement across all 26 counties
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