17 insulation & plastering specialists in Luxembourg

An insulation project rarely touches a single item. Facade renovation, roof replacement, window and exterior door replacement, or installing balanced ventilation are often carried out at the same time, but belong to separate trades with their own permits and their own quotes.

Rising damp, capillary moisture or structural water infiltration must be diagnosed and treated before any insulation work, otherwise moisture gets trapped inside the walls and insulation materials deteriorate.

The load-bearing structure, roof frame or foundations are also outside this trade. If a diagnosis reveals a structural weakness, it must be addressed by a competent professional before insulation work begins, otherwise the installed material risks being damaged by later movement of the building.

Certain signs are hard to miss: cold walls to the touch in winter, recurring condensation on windows or in room corners, heating bills that keep rising without explanation, or noticeable discomfort in summer in rooms under the roof. These all point to insulation that is missing, insufficient or damaged.

In Luxembourg, several obligations apply. An energy passport (passeport énergétique) is required when selling or renting a property; it assesses the building's thermal performance and helps prioritise renovation work. Before starting work for which you intend to apply for subsidies, a myenergy consultation is recommended, and sometimes required, to confirm the technical relevance of the project.

External insulation that changes the appearance of a facade may require a municipal permit, particularly if the added thickness encroaches on public land or changes the building's position relative to plot boundaries. It is worth checking with your municipality's technical department before signing a quote.

In a co-owned building, external insulation affects common areas and generally needs approval at a general meeting before work can start. Internal insulation of a private unit follows more flexible rules, except where it affects a party wall shared with a neighbour.

The first step is a technical site visit, followed by a detailed quote specifying materials, thicknesses, treated surfaces and timelines. For an unconverted attic, the job is often completed in one to two days. Internal wall insulation in an occupied home can take one to two weeks depending on the rooms involved and how the site is organised around furniture.

External insulation (ETICS) is a heavier undertaking: expect generally two to six weeks depending on facade surface area, architectural complexity and weather conditions, since exterior installation is sensitive to weather. Insulating floors or cellars generally takes between a few days and two weeks.

During the works, an occupied home usually remains liveable, except in the case of internal insulation, which temporarily takes the treated rooms out of use during installation and finishing. A good company plans room by room to limit disruption, especially when the site is an occupied main residence.

Clients benefit from preparing in advance: clearing the attic or the rooms concerned, arranging access for materials, planning temporary relocation if rooms become inaccessible, and gathering useful documents such as an existing energy passport or a building plan. A formal handover, checking the continuity of the insulation and the airtightness, closes the project.

The cost of an insulation project depends on several factors, and it is not possible to give a single figure valid for every case. The surface area to be treated and the ceiling height play a direct role, as does the chosen material: bio-based insulants (wood fibre, cellulose, hemp wool) are generally more expensive per volume than standard mineral wool.

The chosen technique strongly influences the budget: external insulation with render or cladding costs more than internal insulation, due to scaffolding, facade finishing and treatment of window sills. Site accessibility, the presence of critical points to treat (roller shutter boxes, junctions, existing networks) and the possible need to remove and reinstall existing elements (cladding, panelling, plasterboard) also add to the cost.

Finally, the targeted performance level, expressed as thermal resistance, has a direct impact on the required insulation thickness and therefore on material volume and labour. Requesting several detailed and comparable quotes remains the best way to place an offer against the market.

As an indicative range, insulating an unconverted attic generally sits in a lower price bracket compared with external insulation, which remains the most expensive intervention per square metre due to scaffolding and facade finishing. These indicative ranges vary considerably from site to site and do not replace a detailed quote issued after a visit.

Mineral wool (glass or rock wool) is the most widely used insulation material in Luxembourg. It offers good value for money, reliable thermal resistance per centimetre of thickness, and good fire performance. Its summer behaviour is weaker than denser materials, though, since its low density gives it a shorter heat storage time.

Wood fibre insulation offers higher density and therefore better thermal lag, which benefits summer comfort in rooms under the roof. It is generally more expensive than mineral wool but appeals to clients who value ecological materials and balanced performance across the year.

Cellulose, usually made from recycled newspaper, is often blown in and works well in irregular cavities, such as existing walls or between rafters. It offers good value for money among bio-based materials but requires skilled installation to avoid settling over time.

Rigid foam boards (PIR, PUR, XPS) offer the highest thermal resistance per centimetre of thickness and are particularly suited when available thickness is limited, such as internal insulation in a tight space. They are less breathable, however, and require careful coordination with the vapour barrier and the building's ventilation.

Choosing between these materials is rarely a matter of good versus bad; it depends on the specific surface being treated, the available thickness, the budget and the client's priorities, whether winter performance, summer comfort or environmental footprint.

Several schemes can reduce the cost of an insulation project in Luxembourg. The Klimabonus Wunnen, which replaced the former PRIMe House programme in 2022 and is run by the State, targets improving the energy performance of existing homes, including insulation, and covers certain insulation-related items under technical conditions.

Additional municipal grants exist in some localities and complement national schemes; their conditions vary from one municipality to another. In addition, the 3 % reduced VAT rate for housing (TVA logement) may apply to renovation works that meet certain criteria, a lever distinct from direct subsidies.

These schemes regularly evolve in their eligibility criteria and procedures. We deliberately do not mention any amounts or deadlines: accurate, up-to-date information is available on guichet.lu, myenergy.lu and klima-agence.lu. A myenergy consultation before works remains the best way to secure a project's eligibility for these grants.

Check that the company holds a business permit (autorisation d'établissement) issued by the Ministry of the Economy for the relevant activity. This permit confirms recognised professional skills and is a legal prerequisite for practising the trade.

Compare quotes on identical bases: same surfaces, same thicknesses, same targeted performance. An unusually low quote can hide insufficient insulation thickness or a failure to treat critical points, which later results in disappointing performance despite the work being carried out.

Ask the company how it handles the relationship between insulation and ventilation: a good company should be able to explain how air renewal will be ensured once the building is made more airtight, even if it does not carry out the ventilation work itself.

A well-run project ends with a formal handover and, ideally, documents confirming the materials installed and their performance. These documents are useful for updating the property's energy passport and for supporting a subsidy application with the relevant bodies.

The thermal bridge is the most common mistake: a break in the insulation at a junction, a balcony or a roller shutter box creates a localised cold spot, a source of condensation and heat loss, even if the rest of the wall is well insulated.

Forgetting ventilation is another widespread mistake. Making a home more airtight without adjusting air renewal encourages moisture, mould and a decline in indoor air quality. Ventilation must be considered from the design stage of the insulation project.

A poorly installed, poorly sealed, or wrongly positioned vapour barrier can trap moisture inside a wall or roof, risking internal condensation and progressive material degradation, sometimes invisible for several years.

Neglecting summer comfort is a less visible but frequent mistake: an insulant chosen only for its winter performance, without considering its thermal lag, can leave rooms under the roof barely liveable during periods of high heat. Some denser bio-based materials offer better summer behaviour.

Finally, undersizing insulation thickness to cut the initial cost is a false economy: insulation work is rarely redone for several decades, and a thickness that is too tight at installation permanently limits the home's energy performance.

Vert.lu is a matching platform. You describe your insulation project once, and the request is forwarded to companies in the network matching your criteria (type of work, location, timeline). You then receive several quotes and remain free to choose which company to work with.

Vert.lu does not carry out any work itself and does not charge the homeowner any fee for this matching service. It is designed to save you time on the research and comparison phase, with no obligation on your part.

A building's airtightness is a distinct topic from insulation itself, though closely linked to it. Leaks around penetrations, window junctions or electrical sockets let heat escape even when the insulation layer itself is intact, and can let moisture into the walls.

A blower door test measures a building's airtightness by creating positive or negative pressure and measuring air exchange. It is often carried out on new builds or major renovations, sometimes as a condition for certain grants, and can reveal leaks using a smoke generator or a thermal imaging camera.

After major insulation work, a blower door test can be worthwhile to confirm the effectiveness of the work, particularly for external insulation or new window installation. Where defects are found, they can often still be corrected with targeted fixes before final completion.