Window Replacement Grants 2026 in Luxembourg: Uw Conditions and Klimabonus Amounts

Introduction: The New Klimabonus Wunnen 2026 Program

Since January 1, 2026, the Klimabonus Wunnen program has officially replaced the old PRIME House system in Luxembourg. This new initiative, managed by the Klima-Agence, aims to encourage homeowners to carry out energy renovation works, including the replacement of window frames and glazing. In this article, we detail the eligibility conditions, grant amounts, and technical criteria related to the Uw value for windows. Whether you own a single-family house or an apartment, understanding these aids can save you thousands of euros.

What is Klimabonus Wunnen 2026?

The Klimabonus Wunnen is the new financial aid system for energy renovation of homes in Luxembourg. It includes several types of subsidies: insulation, heating, renewable energy, and of course, window replacement. This program succeeds PRIME House, which ended in December 2025. Applications are made exclusively online via the Klima-Agence portal, with simplified processing and reduced delays.

The program's goals are clear: reduce the energy consumption of buildings, achieve carbon neutrality by 2050, and improve residents' comfort. For windows, the focus is on very low Uw values, ensuring excellent thermal insulation.

Eligibility Conditions for the Window Frame Grant

To benefit from the window frame grant under Klimabonus Wunnen 2026, several conditions must be met:

• The home must be located in Luxembourg and meet the age requirement (to benefit from the reduced VAT rate).
• Works must be carried out by a company registered in Luxembourg.
• The replaced windows must be in contact with the outside or with an unheated space (garage, cellar, etc.).
• The Uw value (thermal transmittance coefficient of the complete window) must be less than or equal to 0.8 W/m²K.
• If you replace only the glazing (without the frame), the Ug value (glazing alone) must be ≤ 0.5 W/m²K.
• The application must be submitted before the start of works.

There is no income condition: the grant is accessible to all homeowners, whether owner-occupiers or landlords.

Grant Amounts for Window Frames in 2026

The grant amount is calculated based on the surface area of replaced glazing. Here are the main amounts:

The maximum grant is 10,000 EUR per home per year. This cap applies to all window works, but also to other measures like insulation or photovoltaics. For example, if you install solar panels and replace your windows, the total grants cannot exceed 10,000 EUR.

For a typical example: a house with 10 standard-size windows (about 1.5 m² each) represents a total surface of 15 m². The grant would be 15 x 70 = 1,050 EUR. If you have 20 m² of glazing, the grant reaches 1,400 EUR.

The Uw Value: A Key Technical Criterion

The Uw value is the thermal transmittance coefficient of the complete window (frame + glazing). The lower it is, the better the insulation. To qualify for the grant, the Uw value must be less than or equal to 0.8 W/m²K. This requirement is stricter than the current standard for new constructions (often 1.3 W/m²K).

To achieve such performance, it is recommended to opt for:

• Triple glazing with a Ug value ≤ 0.5 W/m²K.
• Frames with thermal break (wood, PVC, aluminum with insulating spacers).
• A low linear transmittance coefficient (Psi) at the frame-glazing junction.

Qualified craftsmen can help you choose certified products. Remember to ask for a technical data sheet with the guaranteed Uw value.

How to Apply for the Grant?

The grant application is made online on the Klima-Agence website. Here are the steps to follow:

1. Create an account on the portal (or use your LuxTrust identifier).
2. Fill in the application form indicating the type of work (window frame replacement).
3. Attach the supporting documents: quote from the company, house plan, photos, etc.
4. Wait for validation of your file (usually 2 to 4 weeks).
5. Once the works are completed, send the paid invoices to receive the grant.

It is important to note that the application must be made before the start of works. If you start works without prior approval, you risk losing the grant.

Other Complementary Aids: Reduced VAT and Insulation Subsidies

In addition to the window frame grant, you can benefit from the reduced VAT of 3% on renovation works, provided the home is meeting the age requirement. This represents a substantial saving, as the normal rate is 17%.

If you take advantage of window replacement to improve the insulation of your roof or walls, know that Klimabonus also offers grants:

• Roof insulation: a rate per square metre insulated, from 35 to 115 EUR/m2 depending on the insulant and the performance standard reached (up to 140 EUR with the transitional increase) (with R ≥ 6 for sarking, R ≥ 7 for attics).
• Wall insulation: a rate per square metre insulated, from 35 to 115 EUR/m2 depending on the insulant and the performance standard reached (up to 140 EUR with the transitional increase).
• Installation of photovoltaic panels: grant of 8,300 EUR for 10 kWp, up to 10,000 EUR for 15 kWp and more.
• Home battery: up to 2,250 EUR.

By combining these aids, you can finance a significant part of your energy renovation project.

Common Mistakes to Avoid and Practical Tips

To maximize your chances of getting the grant, avoid these frequent errors:

• Not checking the Uw value of windows before purchase.
• Doing the works before having obtained the approval from Klima-Agence.
• Forgetting to provide all supporting documents (quotes, invoices, photos).
• Not keeping the original invoices.

It is advisable to consult an energy advisor to assist you in your project. This professional can help you choose the right windows, prepare your file, and optimize the aids.

Conclusion

The Klimabonus Wunnen 2026 program offers an interesting opportunity to replace your window frames at a lower cost. With a grant of 70 EUR/m² and clear technical conditions (Uw ≤ 0.8), you can improve the comfort of your home while reducing your energy bill. Remember to apply before starting the works and to be accompanied by qualified professionals. For more information, consult the official sources mentioned below.