Materials · Detail
HR++ vs triple glazing for a dormer
HR++ is the modern default. Triple is the upgrade people argue about. The honest answer is that one is right for most homes and the other is right for specific ones — and the rest is a matter of comfort, not bills.
5 min leestijd·Onafhankelijke informatie
Short answer
HR++ is the cost-effective default for most dormers — U around 1.1 W/m²K with a warm-edge spacer. Triple glazing drops the U-value to about 0.7, costs 25–40% more, weighs 50% more and is genuinely worth it on south-facing dormers, on noisy streets, or when the project is targeting an energy-label step.
What HR++ actually is
HR++ is double glazing with a low-emissivity coating on one pane and a gas-filled cavity (typically argon) between them. The coating reflects long-wave heat back into the room; the gas slows conduction. The result is a window that loses roughly half as much heat as standard double glazing, at a sensible price point.
What triple adds
- Lower U-value. Roughly 0.7 vs 1.1 for HR++. That means a warmer inside surface and fewer cold draughts near the window.
- Better acoustics. An extra pane and an extra cavity damp out more street noise — useful on busy roads.
- More stable summer temperatures. A coated triple unit can also reduce solar gain, keeping the room cooler in July.
- Costs. 25–40% more than HR++, heavier glass (and so a stronger frame), no real difference in lifespan.
Side-by-side
| Aspect | HR++ | Triple |
|---|---|---|
| U-value (centre of pane) | ≈ 1.1 W/m²K | ≈ 0.7 W/m²K |
| Weight per m² | ≈ 20 kg | ≈ 30 kg |
| Cost (index) | 100 | 125–140 |
| Noise reduction | Average | Markedly better |
| Best for | Most homes | Sun-facing, noisy or label-driven |
| Lifespan of the seal | 20–25 years | 20–25 years |
When triple is actually worth it
- The dormer faces south or south-west and you want to control summer overheating.
- The house sits on a busy road, near a school or under a flight path.
- The project is part of a wider energy upgrade aimed at moving the property's energy label.
- You spend serious time near the window — a desk, a bed-head, a reading chair where comfort matters.
FAQ
FAQ
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01Is HR++ enough today?
For most family homes, yes. HR++ with a warm-edge spacer hits U ≈ 1.1 W/m²K and is the cost-effective default. Triple makes sense on south-facing dormers, noisy streets or homes targeting an energy label step.
02What is the difference between HR++ and triple in real life?
About one comfort step. A triple-glazed dormer feels noticeably warmer in winter near the window, quieter on a noisy street and slightly cooler in summer. The energy bill saving alone is small; the comfort difference is what people notice.
03Is triple glazing heavier?
Yes — roughly 50% heavier than HR++. That means the frame must be specified for the load. A serious quote names the frame's load rating; a vague one does not.
Conclusie
Choose glazing for the room you actually use, not for the spec sheet. HR++ is the right answer for most dormers; triple is the right answer for the specific ones above. Either way, ask the company to name the U-value and the frame's load rating in writing.