Triple vs Double Glazing in Ireland — U-value, Cost, and When Triple Pays Back
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Triple: U-value 0.7–1.0, €800–€1,400/m² window. Double: U-value 1.2–1.4, €450–€750/m². Pays back in 12–18 years.
Triple-glazed windows: U-value 0.7–1.0 W/m²K, €800–€1,400/m² of window installed. Double-glazed: U-value 1.2–1.4 W/m²K, €450–€750/m². Pays back in 12–18 years on heating bills for an A-rated house. Required for Passive House (U-value 0.7–0.8). Most Irish self-builds on BER A1 use triple. Standard A2/A3 builds use double with low-E coatings and warm-edge spacer bars. Frame material matters as much as glazing: uPVC is the cheapest but has the highest whole-window U-value; timber and alu-clad are warmer. A 150 m² house has 25–35 m² of windows (about 15% of floor area).
When this matters most
You're at window choice stage.
When this doesn't apply
You've already specified the windows.
Sources
NSAI, I.S. EN ISO 10077 — Thermal performance of windows, doors and shutters. https://www.nsai.ie/
SEAI, Window performance database. https://www.seai.ie/
Frequently asked questions
Is triple glazing worth it in Ireland?
Depends on BER target. For A1, yes — pays back in 12–18 years. For A2 or A3, double with low-E coatings and warm-edge spacers is enough.
How much do triple-glazed windows cost in Ireland?
€800–€1,400/m² installed. For a 30 m² window schedule: €24,000–€42,000. U-value 0.7–1.0 W/m²K.
What is the Part L 2022 window U-value?
1.4 W/m²K maximum (backstop). For A1 BER: 0.8–1.2 typical. For Passive House: 0.7–0.8.
When this matters most
You're at window choice stage.
When this doesn't apply
You've already specified the windows.
Where to go next
Next decision
The next step in your build sequence.
- Door Budget for a Self-Build in Ireland — Internal Doors, External Doors, and Ironmongery →
- Front Door in Ireland — Composite, Timber, Aluminium, and What the BER Counts →
- Garage Door in Ireland — Sectional, Roller, or Up-and-Over, and What the BER Counts →
- Passive House Windows in Ireland — U-value, Frame, and What the Certifier Wants →
- Sliding Doors in Ireland — Aluminium Sliders, Lift-and-Slide, and the U-value Trade-Off →
- Window Energy Rating in Ireland — What the Label Means and Why It Matters for BER →
- Window Installation in Ireland — Cavity Closer, Dpc, and the Airtightness Detail →
Branch into
Adjacent decisions at the same stage.
Watch out for
Common mistakes, hidden costs, gotchas.
Compare with
Alternative approaches worth knowing.