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Energy renovation in Luxembourg: which works, what cost, what gains?

In Luxembourg, an energy renovation tackles the roof and walls first, which account for almost half of the heat losses of an uninsulated house, then ventilation and heating. For a 1970s-1980s house of about 140 m², allow €45,000–105,000 for the whole envelope, heat-recovery ventilation included, and €57,000–129,000 with a heat pump, excluding VAT and before the Klimabonus.

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Where to start: measure the heat losses before choosing the works

An energy renovation starts with a measurement: the energy performance certificate (CPE, or « Energiepass ») rates your home from A+ to I, and energy advice turns that finding into an ordered, costed works plan. According to our renovation potential survey, 8 out of 10 house owners can gain at least 4 energy classes.

• The certificate assesses three indicators: energy performance (primary energy), thermal insulation (heating demand) and environmental performance (CO₂). It is issued by an architect or consulting engineer registered with the OAI, or by an approved expert, and is valid for 10 years. Its price is not regulated: allow roughly €500 to €600 for a house. A grant file needs one before and one after the works. See the energy performance certificate in Luxembourg.
• Energy advice from an approved advisor is mandatory as soon as the renovation covers more than one element or includes ventilation. It sets the order of works, the thicknesses and target standards, then checks the quotes and the site. Role, fees and how to choose: energy advisors in Luxembourg.
• Klima-Agence’s basic advice is free, at home, by video call or on 8002 11 90. It helps you get your bearings but does not replace the approved advisor.

The full procedure, document by document, is described in our Klimabonus application steps.

Which works first: the order that avoids paying twice

The order that avoids rework is simple: envelope first, ventilation next, heating after that, energy production last. As each element is only subsidised once, aim straight for the right performance level.

Thermal insulation in Luxembourg: items, prices and requirements

Insulating the envelope is the main lever: in an uninsulated house, the roof and walls alone account for almost half of the heat loss. Here, item by item, are the installed prices seen in 2026 and the minimum insulation thickness required for the Klimabonus.

Loss shares are commonly accepted orders of magnitude for an uninsulated house; prices are market ranges excluding VAT, supply and fitting included (renov.lu survey, September 2026, detached house). To compare materials, see our insulation materials comparison.

Thermal bridges: finding and treating them

A thermal bridge is a spot where the insulation is interrupted, such as a balcony slab, a lintel, a floor edge or the wall-roof junction: heat escapes there and moisture condenses, which is why mould appears in corners.

• Finding them: an infrared thermal survey (€200 to €600) makes them visible between November and March, with at least 10 °C difference between inside and outside. A corner of wall that feels cold to the touch is often the sign.
• Treating them: external insulation removes most thermal bridges by wrapping the façade without a break. The remaining points are handled case by case: insulation returned into window reveals, wrapped or thermally broken cantilevered balconies, continuity between wall and roof insulation.
• Having them calculated: within energy advice, the thermal bridge calculation is subsidised if the home reaches class C (see the energy advice grants).

Internal insulation leaves thermal bridges at floor slabs and cross walls: extend the insulation a few tens of centimetres onto the ceilings and floors concerned.

Ventilating an insulated home

A home whose walls have been insulated and windows replaced becomes airtight: without mechanical ventilation, the moisture from cooking, showers and breathing builds up and condenses on cold surfaces.

• Heat-recovery ventilation (MVHR): it recovers heat from the extracted air to warm the incoming air; it is the only ventilation subsidised by the Klimabonus, within energy advice, with at least 80% efficiency and an airtightness test of n50 ≤ 2.0 h⁻¹. Prices, grants and choice: heat-recovery ventilation in Luxembourg.
• Humidity-controlled extract ventilation: cheaper and with no supply ducts, but without heat recovery or grant. Price grid for every system: ventilation installation costs.
• Measuring airtightness: the Blower Door airtightness test checks the result and is a condition for the ventilation grant.

Replacing the heating: heat pump, wood or heat network

Once the envelope is insulated, replace oil or gas heating with a heat pump, a pellet boiler or a heat-network connection: these are the only subsidised heating options, as a new fossil boiler no longer is.

• No ban prevents replacing an oil or gas boiler in an existing home; in new builds, performance requirements have ruled it out in practice since 2023.
• Air-to-water heat pump: €12,000 to €24,000 installed, according to installers. Sized after insulation, it is smaller and more efficient. Its outdoor unit must meet municipal rules (as a rule 40 dB(A) at the neighbouring buildable plot and a 2-metre setback under the model regulation) and it is inspected 1 to 2 years after commissioning, then every 4 years.
• Existing boiler: inspection remains mandatory every 2 years for oil and every 4 years for gas.

Further reading: heat pumps in Luxembourg, their installed cost and replacing an oil boiler.

Producing your own energy: photovoltaics and solar thermal

Solar panels lower the home’s primary energy and therefore its energy performance class; they come last, on a roof that has already been renovated if it needed to be.

• For a new system you must choose between the feed-in tariff guaranteed for 15 years and the Klimabonus with self-consumption: the two cannot be combined. Installed photovoltaics are invoiced directly at 3% VAT.
• Solar thermal for hot water is still subsidised in existing homes, no longer in new builds.
• A balcony solar kit under 800 W does not need to be declared to the grid operator, but it is neither subsidised nor paid for its surplus.

Sizing, profitability and procedures: solar panels in Luxembourg.

Energy renovation of a detached house: three scenarios

For a detached house, three scenarios cover most projects, from the roof alone to a complete renovation; the budgets below are installed prices excluding VAT and before grants (renov.lu survey, September 2026) for a house from the 1970s-1980s of about 140 m².

Grant amounts for each item and a fully calculated example are on our page on grants and the 2026 Klimabonus; the detailed budget by item is in the cost of an energy renovation. Houses from the 1960s to 1980s have their own weak points (balcony slabs, poorly insulated roofs): see renovating a 1960s-80s house, and for a terraced house, party walls are insulated from inside.

Flat in a co-owned building: what the general meeting decides

In a flat, the energy certificate covers the whole building, and the works that change its class (façade, roof, shared heating) are decided by the co-owners’ general meeting.

• Since 1 October 2022, energy renovation, technical ducts and the production or storage of renewable energy in common parts are voted by a majority of the votes of all co-owners (amended law of 16 May 1975).
• A co-owner who wants to carry out, at their own cost, works affecting common parts or the exterior (decentralised ventilation through the façade, for instance) needs the same majority.
• A works fund has been mandatory since 1 August 2023; a co-ownership’s grant file is collective.
• In your own flat, with no vote: internal wall insulation (grant reduced by 25%) and, if the rules allow, window replacement.

See also renovation in co-owned buildings (votes, collective grants) and heat pumps in co-owned buildings.

Permits and rules to know

In Luxembourg, your municipality decides whether energy renovation works need a building permit, a simple declaration or nothing, according to its building regulation.

• Model regulation recommended to municipalities (2023): insulating a façade or roof without a significant change of appearance is exempt from a permit outside protected buildings; external insulation may exceed building lines, setbacks and heights by up to 0.50 m; solar panels are exempt outside protected buildings. Each municipality only applies it if it has adopted it: in Luxembourg City, refurbishing a façade or roof requires a declaration, and a permit in a protected area.
• Timelines: with no decision after 3 months, the request may be treated as refused; a permit is valid for 2 years and can be extended once by one year; appeals are possible for 3 months.
• Listed building: written authorisation from the Minister of Culture, supported by the National Institute for Architectural Heritage. Green zone: authorisation from the Minister of the Environment.

Municipal procedures in detail: building permits and works declarations.

Grants: three rules to know before signing

Three rules decide your grants before the works even start: the approval in principle is requested before insulation, window and ventilation works, but after installation for a heat pump, solar panels or a pellet boiler; energy advice is mandatory as soon as you renovate more than one element or install ventilation; the home must be more than 10 years old, as for the 3% VAT rate, which also requires a main residence. Forms, EPC before and after the works, deadlines and payment: follow our Klimabonus application steps. 2026 amounts by type of works: grants and the 2026 Klimabonus; VAT procedure: 3% VAT. In 98 of the 100 communes, the commune adds its own grant: commune grant amounts, commune by commune. For offices, a workshop or a shop, the grants are different: see grants for business energy renovation.

Eco-friendly renovation: which materials to choose

An eco-friendly renovation favours bio-based insulation (wood fibre, cellulose, hemp), which is also the best subsidised by the 2026 Klimabonus, whereas non-recycled fossil insulation (polystyrene, polyurethane) is no longer subsidised at all on a façade or roof.

• Insulation counts as « ecological » for the Klimabonus if it is over 70% plant or animal material; a bonus is added if it comes from certified sources (FSC, PEFC, natureplus).
• Mineral insulation with over 50% recycled content and a green roof or façade also earn a bonus.
• A façade insulated with wood fibre under mechanically fixed timber cladding is the best subsidised solution of all.

Properties and limits of each material: our insulation materials comparison.

Estimate your renovation

The energy renovation simulator suggests an order of works and calculates the 2026 grants for your home. For a specific project, three companies established in Luxembourg send you a quote within 48 working hours. For a single item, such as windows, insulation or heating, you can also find a verified tradesperson by choosing the trade.

Frequently asked questions about energy renovation in Luxembourg