Triple glazing windows in Luxembourg 2026: prices, performance and subsidies
Triple glazing achieves a thermal coefficient of Uw 0.6–0.9 W/m²K, versus 1.0–1.3 W/m²K for modern double glazing — delivering up to 30% additional heating savings. In Luxembourg, this performance is directly rewarded by the Klimabonus 2026 and Enoprimes grants, which can be combined with 3% VAT and municipal subsidies. For a standard window, total aid reaches up to €146 per window (Klimabonus + Enoprimes), and up to €465 for a bay window. Key condition: obtain the MyGuichet.lu prior approval before signing your order — this rule applies without exception.
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Triple vs double glazing: full comparison
Both work on the same principle: trapping gas (argon or krypton) between glass panes to limit heat exchange. Triple glazing adds a third pane and a second gas cavity, creating a significantly superior thermal barrier. The trade-off: frames are 50% heavier (around 30 kg/m² vs 20 kg/m²), slightly thicker (36–44 mm vs 24–28 mm) and natural light transmission is marginally reduced (approximately 5–10%). For a full analysis of the choice between the two, see our guide on double vs triple glazing in Luxembourg.
| Feature | Modern Low-E double glazing | Argon/krypton triple glazing |
|---|---|---|
| Thermal coefficient Uw | 1.0 – 1.3 W/m²K | 0.6 – 0.9 W/m²K |
| Total thickness | 24 – 28 mm | 36 – 44 mm |
| Acoustic insulation Rw | 30 – 34 dB (standard) 38 – 42 dB (acoustic specialist) | 32 – 36 dB Not better than acoustic double |
| Solar factor g | ≈ 0.60–0.65 (high gains) | ≈ 0.45–0.55 (reduced gains) |
| Light transmission Tl | ≈ 80% | ≈ 68–72% |
| Heating savings vs single glazing | up to 20% | up to 30% |
| Klimabonus eligibility (Uw ≤ 1.0 W/m²K) | Depends on model (high-end) | Yes, systematically |
| High tier eligibility (Uw ≤ 0.8) | Rarely | Yes (high-performance frame required) |
| Standard window installed price (Luxembourg) | €500 – €650 | €750 – €950 |
| Indicative lifespan | 25 – 30 years | 25 – 35 years |
| Glazing weight | ≈ 20 kg/m² | ≈ 30 kg/m² (+50%) |
For passive houses and renovations targeting energy class A in Luxembourg, triple glazing is virtually essential. For a standard renovation of a 1970–1990 home, high-quality double glazing (Uw ≤ 1.0 W/m²K) may be sufficient to unlock basic Klimabonus grants. But triple glazing gives access to the highest subsidy rates and delivers superior long-term energy savings — particularly on north-facing façades where solar gains are absent.
The Uw coefficient: how to read it and why it matters
The Uw coefficient (W/m²K) measures total heat loss through the complete window — glazing and frame — per square metre per degree. The lower the value, the better the insulation. It is the only coefficient used for Klimabonus eligibility — not Ug (the glazing-only coefficient). Levels apply to windows of the standard dimensions 1.23 m × 1.48 m (the official Guichet.lu reference size).
| Performance level | Required Uw | Corresponding glazing | Grant rate |
|---|---|---|---|
| Minimum insulation | Uw ≤ 1.0 W/m²K | High-end double or standard triple glazing | Base rate |
| Enhanced insulation | Uw ≤ 0.9 W/m²K | High-performance triple glazing | Increased rate |
| High insulation | Uw ≤ 0.8 W/m²K | Premium triple glazing (argon/krypton) | Maximum rate |
The Uw coefficient covers both glazing (Ug) and frame (Uf). A triple-glazed unit may show an excellent Ug (0.5 W/m²K) but if the frame is poor quality (Uf = 1.8 W/m²K), the overall Uw of the assembled window can remain at 1.1 W/m²K — insufficient for the Klimabonus threshold. Always demand the Uw of the complete installed window, certified by a product technical datasheet.
Klimabonus requirements for windows are also conditional on the thermal performance of the adjacent wall. For the highest rates, the exterior wall must achieve Uwall ≤ 0.85/0.80/0.75 W/m²K per tier — or the home must have double-flow mechanical ventilation.
When to choose triple glazing in Luxembourg?
Triple glazing is not always the best choice. Its value varies significantly depending on project type, building orientation, and the overall state of the thermal envelope.
New build or full renovation targeting class A or passive standard
Triple glazing is practically mandatory to achieve Passivhaus standards or energy class A in Luxembourg. Since 1 January 2017, all new buildings must meet the passive standard, which includes windows with Uw ≤ 0.8 W/m²K. If your project aims to improve your energy rating to class A or B, triple glazing fits this logic.
North or north-east facing façades
North-facing façades receive no passive solar gain in winter. Triple glazing’s 30–40% improvement in Uw over double glazing is fully valorised there. For south façades, the calculation is more nuanced — our guide on double vs triple glazing details this.
Home already well insulated (walls, roof, ground floor)
Triple glazing’s benefit is maximised when the overall thermal envelope is already performant. If your home already has external wall insulation or roof insulation, triple glazing becomes highly relevant to complete the envelope.
Colder communes in the Luxembourg Ardennes
In the Ardennes region (Clervaux, Wiltz, Vianden, Troisvierges, Weiswampach…), winter temperatures are notably lower. The higher heating degree-days significantly improve the return on investment for triple glazing, shortening its payback period versus the national average.
Maximising Klimabonus grants
Triple glazing systematically achieves the Uw ≤ 1.0 W/m²K Klimabonus threshold and qualifies for the enhanced rates (Uw ≤ 0.9 or ≤ 0.8 W/m²K). Note however that the grant difference between minimal and high tier is only about €20 per standard window — the economic case must rest primarily on long-term energy savings.
In an older home where walls and roof are not insulated, triple glazing alone will have limited impact. Guichet.lu conditions certain window grant levels on a minimum wall quality (Uwall ≤ 0.85 W/m²K). If in doubt, see our guide on where to start your energy renovation, or consult a Klima-Agence accredited energy advisor.
PVC, aluminium or wood: which frame with triple glazing?
The frame material directly affects the overall Uw, durability, maintenance and cost. In all cases, installation is handled by a professional window fitter — always compare at least three quotes.
| Material | Typical frame Uf | Durability | Maintenance | Relative cost | Klimabonus eligible |
|---|---|---|---|---|---|
| Multi-chamber PVC | 1.0 – 1.4 W/m²K | 25 – 30 years | Very low | Reference | Yes |
| Thermally broken aluminium | 1.4 – 2.0 W/m²K | 40 – 50 years | Very low | +20 to +30% | Yes (if overall Uw ≤ 1.0) |
| Wood | 1.1 – 1.5 W/m²K | 30 – 40 years (if maintained) | Moderate (painting/staining) | +15 to +25% | Yes |
| Composite wood-aluminium | 1.0 – 1.3 W/m²K | 35 – 45 years | Low (ext. alu) | +25 to +40% | Yes |
For aluminium frames, the quality of the thermal break is critical. Insist on a thermal break of at least 24 mm to achieve a competitive overall Uw with triple glazing. A low-quality aluminium frame (12–14 mm thermal break, Uf = 1.8 W/m²K) combined with an excellent triple-glazed unit can result in a final Uw of 1.1 W/m²K — below the minimal Klimabonus threshold. Always verify the thermal break width on the manufacturer’s technical datasheet.
Triple glazing window prices in Luxembourg in 2026
Prices include supply and professional installation in Luxembourg. For a full analysis of window costs, see our guide on window prices in Luxembourg.
| Window type | Double glazing (reference) | Triple glazing | Triple premium |
|---|---|---|---|
| Standard window (1.23 × 1.48 m) | €500 – €650 | €750 – €950 | +30 to +50% |
| French door | €800 – €1,300 | €1,200 – €1,800 | +30 to +45% |
| Bay window | €1,900 – €2,500 | €2,400 – €3,300 | +25 to +35% |
| Roof window (Velux type) | €600 – €900 | €900 – €1,300 | +30 to +45% |
For a medium-sized Luxembourg home (130–160 m²), the total budget for replacing all windows with triple glazing typically ranges between €20,000 and €40,000. Always request at least three comparative quotes from different certified installers — price differences can exceed 40% for identical work.
2026 grants: Klimabonus + Enoprimes + municipal aid
Window replacement is eligible for several stackable grants in Luxembourg. For a full overview, see our page on Klimabonus 2026 grants.
Klimabonus 2026 — simplified route vs full route
- Simplified route (single element): windows only, no energy audit required. Prior approval via MyGuichet.lu mandatory before works.
- Full route (with energy audit): windows as part of a broader project. Delivers the highest rates. See our guide on energy renovation steps in Luxembourg.
| Window type (standard size) | Indicative Klimabonus + Enoprimes Minimum insulation (Uw ≤ 1.0) |
Indicative Enhanced (Uw ≤ 0.9) |
Indicative High (Uw ≤ 0.8) |
|---|---|---|---|
| Standard window (1.23 × 1.48 m) | ≈ €126 | ≈ €137 | ≈ €146 |
| French door | ≈ €211 | ≈ €227 | ≈ €242 |
| Bay window | ≈ €405 | ≈ €435 | ≈ €465 |
Source: Guichet.lu and Enoprimes.lu — combined Klimabonus 2026 + Enoprimes for standard sizes. Indicative amounts; verify exact figures via the Klima-Agence simulator.
Enoprimes must be requested before signing the order form — without exception. If this step is missed, the grant is permanently lost.
3% VAT
Reduced 3% VAT applies to renovation works on a Luxembourg primary residence over 2 years old, capped at €50,000 of recoverable VAT. On a €15,000 window replacement, this saves €720 compared to the standard 17% rate.
Net cost = Works price (excl. VAT) − Klimabonus − Enoprimes − VAT saving (17%→3%) − Municipal grantsExample for 10 standard triple-glazed windows (Uw ≤ 0.9):
Price excl. VAT: €8,500 | Klimabonus + Enoprimes: ≈ €1,370 | VAT saving: ≈ €1,190
→ Estimated net cost: ≈ €5,940 (before any municipal grants)
Calculate your exact triple glazing grants
Our simulator integrates the 2026 Klimabonus, Enoprimes and municipal grants for your Luxembourg window project.
Klimabonus technical conditions for windows
To be eligible for the Klimabonus 2026, installed windows must meet technical conditions defined by Guichet.lu.
Building over 10 years old
The Klimabonus applies to residential buildings whose building permit was issued more than 10 years ago. The relevant date is that of the building permit issuance.
Uw ≤ 1.0 W/m²K minimum (base level)
The entry threshold for the Klimabonus on windows. Ensure the certified Uw is that of the complete installed window (frame + glazing + spacer), not just the glazing unit.
Adjacent wall or double-flow VMC condition
For certain performance levels, window replacement must be combined with a sufficiently insulated exterior wall (Uwall ≤ 0.85/0.80/0.75 W/m²K per tier) or a double-flow VMC system.
One Klimabonus per element per property
The Klimabonus can only be granted once per construction element for a given property. Previous grants under RGD 2022 or PRIMe House preclude a new Klimabonus for the same element.
Specific case: roof windows (heated attic)
If the attic is heated, roof renovation must include replacement of roof windows over 10 years old with Uw > 1.4 W/m²K. The new roof window must achieve Uw ≤ 1.4 W/m²K.
Accredited installer and technically compliant invoice
The invoice must state the certified Uw of each installed window, dimensions, glazed area, brand and frame material. An incomplete invoice leads to automatic rejection of the Klimabonus application.
How to apply for triple glazing grants: step-by-step
The chronological order of steps is imperative. For the complete overview, see our guide on energy renovation steps in Luxembourg.
Enoprimes request — before signing the order form
The most critical step. Enoprimes must be requested before signing the order form. If this step is missed, the grant is permanently and irrevocably lost.
Klimabonus prior approval via MyGuichet.lu — before works
Before starting works, obtain prior approval via MyGuichet.lu using form DEPA-2026. Without this, no Klimabonus will be paid regardless of execution quality.
Check for municipal authorisation
Depending on window type, colour or property characteristics (listed building, protected zone), a municipal permit may be required before works begin.
Works carried out by the certified installer
The invoice must state the certified Uw of each window, dimensions, brand, frame material and glazing type. Keep all technical documents.
Submit the Klimabonus payment request
After receiving the final invoice, file the liquidation request on MyGuichet.lu. You have up to 4 years after 31 December of the invoice year to submit.
Check for municipal grants
Check with your municipality for additional energy renovation grants. These must generally be applied for before works begin.
Simplify your admin: our certified partner installers in Luxembourg handle Klimabonus and Enoprimes formalities on your behalf.
Find a certified installer →Common mistakes to avoid when replacing windows in Luxembourg
Signing the order form before requesting Enoprimes. This mistake is irreversible: once the order form is signed, the Enoprimes application is automatically and definitively rejected.
Starting works without Klimabonus prior approval. The MyGuichet.lu prior approval is mandatory before any work begins. If works start without it, the Klimabonus grant is refused without exception or recourse.
Choosing triple glazing without checking the complete assembled window Uw. Always require the Uw of the complete installed window certified by a manufacturer datasheet — not just the glazing unit Ug.
Installing triple glazing without checking the adjacent wall condition. If walls do not meet Uwall ≤ 0.85 W/m²K and you have no double-flow VMC, certain Klimabonus levels will not be accessible.
Frequently asked questions about triple glazing in Luxembourg
No. The Klimabonus is accessible as soon as the installed window’s Uw is ≤ 1.0 W/m²K, a threshold some high-end Low-E argon double-glazed windows can reach. However, triple glazing systematically meets this threshold and also qualifies for the higher rates (Uw ≤ 0.9 or ≤ 0.8 W/m²K). For a full analysis, see our guide on double vs triple glazing.
Yes. It is not necessary to replace all windows. The Klimabonus can be obtained for a partial replacement. However, the grant can only be awarded once per construction element for a given property.
Yes, but the impact depends on the overall thermal envelope. Triple glazing delivers up to 30% heating savings versus single glazing, and approximately 10–15% more than modern well-insulated double glazing. In a medium-sized Luxembourg home, these savings typically represent €200–500 per year. Return on investment is typically 15 to 25 years under average Luxembourg conditions.
Yes. The Klimaprêt is a subsidised-rate loan from state-approved Luxembourg banks (including BCEE). There is no incompatibility between the Klimabonus and the Klimaprêt: both can be used together for the same project.
Not necessarily. For windows-only replacement (single thermal envelope element), you can use the simplified Klimabonus route, which does not require a full energy audit. If you plan to renovate several elements simultaneously, the full energy advisory report is mandatory and unlocks the highest subsidy rates.
Slightly — around 5 to 10% less than equivalent Low-E double glazing. In practice, this is barely noticeable with modern high-transmission glazing. For light-sensitive rooms (large south-facing bays, verandas), choose a triple-glazed unit with Tl ≥ 70%.
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