Insulation & Energy Renovation Subsidies

What the public support covers

Insulation work on the building envelope falls under the Klimabonus Wunnen: roof, external walls, ground floor and window replacement are each treated as a separate strand of the scale, with its own technical requirements. A renovation combining several of these does not merge into one file: each strand must meet its own performance criteria.

The amounts, caps and thermal performance requirements applicable at the time of your application are published on guichet.lu. Do not rely on a figure quoted elsewhere without checking it against the official sheet, as these scales change.

The central role of the energy passport

The building's energy passport (Energiepass) documents its thermal condition before works and serves as the reference for judging the value of a renovation. It is often requested to process a subsidy application, particularly when several elements are renovated at the same time, as it lets the overall coherence of the project be checked.

Beyond the passport, every insulation material installed must be documented: thickness, thermal conductivity, product data sheet. This documentation, compiled by the company, proves that the performance required by the relevant strand is met — a simple mention of 'enhanced insulation' on the invoice is not enough.

Renovating in stages without losing coherence

Few households insulate roof, walls, floor and windows in the same year. Staged renovation is common and eligible item by item, provided each stage separately meets the technical requirements of its strand. The value of an energy passport drawn up beforehand lies precisely in ranking the priorities: starting with the roof or the walls depending on the building's actual heat losses, rather than aesthetic preference.

Poorly sequenced insulation can create moisture or condensation problems if airtightness and ventilation are not rethought at the same time. This is a point the company must raise before work starts, independently of the subsidy question.

Why advice before the first invoice matters

Free energy advice from Klima-Agence before committing to the first item of work helps set the priority order of interventions and checks whether prior approval is required for the relevant strand. In several strands of the Klimabonus Wunnen, this approval must be obtained before work starts: beginning a project without this step can make the file ineligible, even if the works otherwise meet the technical criteria.

This initial advice also avoids over- or under-sizing insulation relative to the rest of the project, for instance if a heat pump or mechanical ventilation is planned later on.

Process, documents and combining with other works

The sequence to follow stays constant: energy advice, a detailed quote from a company authorised for the relevant trade, prior approval where the strand requires it, the works, an invoice detailing materials and surfaces, then submitting the file with technical data sheets and, depending on the strand, the energy passport. Insulation can be combined with a heating replacement or a solar installation, but each strand is processed on its own.

Frequent rejections stem from incomplete material documentation, a quote that does not detail surfaces and thicknesses per item, or works started before the required prior approval. Communal subsidies, separate and varying by commune, add to the national scheme: check with your commune's technical department.

Where to find binding figures

Thermal performance criteria and amounts per strand are published on guichet.lu and should guide material choices from the quote stage. Klima-Agence remains the free point of entry to clarify the order of works and check eligibility before any commitment.