The short answer
For a new-build or deep-retrofit aiming at A-rated BER, triple glazing makes sense. For a typical 1970s–1990s Irish semi-D doing a window replacement as part of a moderate fabric upgrade, double glazing with a low-emissivity coating and argon fill is usually the better cost-performance balance. The 30–50% upcharge for triple glazing rarely pays back in heat savings alone within 15 years.
| Modern double (Ar fill, low-E) | Triple (Ar fill, low-E) | |
|---|---|---|
| Whole-window U-value | 1.2–1.4 W/m²K | 0.8–1.0 W/m²K |
| Centre-pane U-value | 1.0–1.2 | 0.5–0.7 |
| Cost per uPVC window | €350–€600 | €480–€800 |
| Cost premium | — | +€100–€220 / window (+30–40%) |
| Annual saving (vs old single) | €280–€420 | €320–€480 |
| Annual saving (vs modern double) | baseline | €40–€80 only |
| Payback on the upgrade alone | — | 20–35 years |
| Weight | Standard | ~50% heavier — hardware spec matters |
Where triple glazing earns its place
- New builds and deep retrofits targeting A-rated BER. The fabric performance has to come from somewhere — windows are the biggest fabric weakness after the door — and a triple-glazed window with a U-value below 1.0 is now the path of least resistance.
- North-facing or shaded elevations where you get the heat-loss penalty without much solar-gain benefit.
- Sound-sensitive locations — main road, flight path, busy urban frontage. The acoustic improvement of triple over double is real and meaningful.
- If you're already doing the work — replacing all windows in one job — the marginal cost of upgrading to triple is lower than retrofitting later. Pay once.
Where double glazing wins
- Single-window replacements in mid-life houses where the rest of the fabric is at typical retrofit standard. The marginal benefit is small.
- South-facing rooms with significant solar gain — triple glazing reduces the gain on top of reducing the loss; sometimes net-net you're worse off in heating-season comfort.
- Listed and conservation-area properties where slim-frame timber sash is the right answer aesthetically — triple-glazed sash exists but premium and heavy.
- Tight budgets where the €100–€220 per-window premium would be better spent on attic insulation, cavity insulation, or a heat pump.
The practical things installers don't tell you
- Triple glazing is heavier. Hinges, friction stays, and locks need higher-rated hardware. Don't accept standard hardware on triple-glazed casements — spec heavy-duty.
- Whole-window U-value matters more than centre-pane. Many quotes show centre-pane (which flatters the spec) — ask for whole-window.
- Edge spacers matter. Warm-edge spacers (Swisspacer, Edgetech) outperform aluminium spacers and reduce condensation. Spec them.
- Argon vs krypton fill: argon is standard; krypton (smaller cavities, slightly better U-value) is premium. For most retrofits, argon is enough.
- Solar Heat Gain Coefficient (SHGC, also called g-value) matters for south-facing rooms — high SHGC keeps useful solar gain; low SHGC reduces summer overheating. Specify by room orientation if you can.
The Cork installer angle
Cork uPVC installers like HPS Group (Carrigaline) carry both A-rated double and triple-glazed options. Specialist suppliers carry deeper spec ranges including aluclad and aluminium triple-glazed for premium retrofits. See the Cork window installers comparison.
Rule of thumb: If you're doing the whole house in one job and aiming for B2 or better, go triple. If you're replacing windows in 2–3 rooms in isolation and the rest of the house won't be upgraded, go double. The fabric has to be balanced — top-spec windows in an under-insulated house are a waste.