Triple vs Double Glazing in Ireland — U-value, Cost, and When Triple Pays Back

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).

TL;DR

• Triple-glazed: U-value 0.7–1.0 W/m²K, €800–€1,400/m² window installed. Double-glazed: U-value 1.2–1.4, €450–€750/m² window.

• Pays back in 12–18 years on heating bills for an A-rated house. Required for Passive House.

• Most Irish self-builds on BER A1 use triple. Standard A2/A3 builds use double with low-E coatings.

When this matters most

You're at window choice stage.

When this doesn't apply

You've already specified the windows.

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.

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/