Klimabonus Wunnen 2026: Roof Insulation R-Value 6 or 7

Klimabonus Wunnen 2026: What Changes for Insulation

Since January 2026, the Klimabonus Wunnen program has replaced PRIMe House. This new scheme, managed by Klima-Agence and Guichet.lu, continues to support energy renovation but with stricter performance criteria. For roof insulation, the aid can cover up to 50% of costs, with a cap of EUR 15,000. However, to benefit, your project must meet a minimum thermal resistance: R ≥ 6 m²K/W for sarking (external insulation) or R ≥ 7 m²K/W for lost attics. But what do these values mean in practice?

Thermal resistance R measures a material's ability to resist heat flow. The higher the R, the better the insulation. In Luxembourg, the continental climate imposes strict requirements to maximize energy savings and reduce carbon footprint. Klimabonus Wunnen 2026 aligns with these goals by conditioning its aid on these minimum thresholds.

R = 6 or 7: What Does It Mean in Practice?

R (thermal resistance) is expressed in square meters kelvin per watt (m²K/W). It depends on the thickness and thermal conductivity (lambda) of the insulation. For example, to achieve an R of 6 with rock wool (lambda = 0.035 W/mK), you need a thickness of about 21 cm. With a more efficient insulator like polyurethane (lambda = 0.022 W/mK), 14 cm is enough.

In the case of a sarking roof (insulation installed externally, under the covering), the target R ≥ 6 ensures excellent performance. For lost attics, where insulation is laid horizontally on the floor, the threshold is higher (R ≥ 7) because heat loss by convection is greater. This means you may need to opt for a greater thickness or a more efficient material.

Concretely, an R of 6 or 7 significantly reduces heat loss. A poorly insulated roof can account for up to 30% of a house's heat loss. By meeting these thresholds, you improve comfort in both winter and summer and reduce your heating bill significantly.

Klimabonus Wunnen 2026 Grants for Insulation

Klimabonus Wunnen 2026 offers a generous subsidy for roof insulation, provided the R requirements are met. Here are the key points:

• Subsidy rate: 50% of eligible costs (materials and labor).
• Cap: EUR 15,000 per dwelling.
• Conditions: R ≥ 6 for sarking, R ≥ 7 for lost attics.
• Combination: possible with the super-reduced VAT of 3% for homes older than 2 years.

To benefit from the aid, you must use a certified craftsman and provide performance proof (technical data sheets, R calculations). The application is made online via Guichet.lu or Klima-Agence. Payment occurs after validation of the work.

Note: Klimabonus Wunnen 2026 definitively replaces PRIMe House since January 2026. Old PRIMe House files are no longer accepted. So make sure to submit your application under the new regime.

How to Achieve the Required R? Choice of Materials and Thicknesses

To achieve an R of 6 or 7, several solutions are available. The choice depends on your roof configuration and budget. Here is a comparative table of common insulators:

As the table shows, the lower the conductivity, the smaller the required thickness. For sarking, external insulation easily achieves R=6 with 21 cm of mineral wool. In lost attics, where R=7 is required, you will need to either increase the thickness or choose a more efficient insulator like polyurethane.

It is essential to have your craftsman calculate the R precisely. A thickness error could compromise eligibility for the subsidy. Moreover, insufficient insulation will lead to thermal bridges and excessive condensation, harming the durability of your roof.

Typical Example: How Much Does Eligible Insulation Cost?

Let's take an illustrative case: a single-family house in Luxembourg City with a 100 m² pitched roof to insulate with sarking. The goal is to achieve R=6. The craftsman proposes 22 cm rock wool (R≈6.3) with new covering. The quote amounts to EUR 18,000 including VAT (materials and labor).

With Klimabonus Wunnen 2026, the subsidy covers 50% of eligible costs, i.e., EUR 9,000. Since the cap is EUR 15,000, you receive EUR 9,000. Additionally, the super-reduced VAT of 3% applies (home older than 2 years), reducing the initial bill. In the end, your out-of-pocket cost is about EUR 9,000, with estimated energy savings of EUR 1,200 per year on heating. The return on investment is about 7 to 8 years.

Another illustrative case: an 80 m² lost attic. To achieve R=7, 30 cm of cellulose wadding is used (R≈7.5). The cost is EUR 6,000. The 50% subsidy gives EUR 3,000. With 3% VAT, the out-of-pocket cost is EUR 3,000. Annual savings are about EUR 600.

These examples show that Klimabonus Wunnen 2026 makes high-performance insulation very accessible, especially when combined with reduced VAT.

Other Klimabonus Wunnen 2026 Grants

Klimabonus Wunnen 2026 is not limited to roof insulation. It also includes subsidies for other energy renovation work:

• Windows: EUR 70 per m² of glazing replaced (with high-performance double or triple glazing).
• Photovoltaic panels: up to EUR 10,000 (about EUR 8,300 for a 10 kWp installation, cap reached from 15 kWp).
• Home battery: up to EUR 2,250 to store solar energy.

These grants are cumulative within the overall caps. For example, you can insulate your roof, replace your windows, and install solar panels, all subsidized. The 3% VAT also applies to all this work for homes older than 2 years.

To benefit from these grants, you must meet the technical criteria specific to each equipment. For example, for windows, the thermal transmittance coefficient (Uw) must be less than or equal to 1.1 W/m²K. For photovoltaics, the installation must be carried out by a certified installer.

How to Apply?

The application for Klimabonus Wunnen 2026 is done in several steps:

• Obtain a detailed quote from a certified craftsman, including the R calculation.
• Submit the file before starting work on the Guichet.lu portal or via Klima-Agence.
• Provide paid invoices and performance proof after work.
• Receive the subsidy payment within a few weeks.

It is recommended to be accompanied by an energy advisor to prepare the file. Klima-Agence offers free consultations. Also, ensure your craftsman is properly registered and complies with Luxembourg standards.

Warning: applications must be submitted before work begins. No subsidy will be granted for work already done without prior authorization.

Conclusion: A Profitable and Ecological Investment

Achieving an R of 6 or 7 is not just an administrative requirement to obtain Klimabonus Wunnen 2026. It is a guarantee of durable energy performance. By properly insulating your roof, you reduce your heating consumption, improve your comfort, and add value to your property. With a subsidy covering up to half the costs and 3% VAT, the return on investment is quick. Don't wait to consult a professional and take advantage of these generous grants.