FAQ

When replacing windows, one should take care to ensure that the walls are properly insulated. If the energy quality of the window is higher than that of the wall, humidity can condense on the walls, thus giving rise to the formation of mould. Condensation always appears in the coldest places.

To benefit from Klimabonus support, the performance of the wall insulation must be higher than that of the new window, or the windows must be replaced and controlled mechanical ventilation installed. When replacing windows, it may therefore also be necessary to insulate the façade. Contact your Klima-Agence adviser to determine the insulation performance of your building (free energy assessment).

In any case, after your windows have been replaced, proper daily ventilation must be ensured to maintain a healthy climate in your home.
 

When windows are not properly sealed, it leads to insufficient and unreliable ventilation and generally prevents correct ventilation in a dwelling. Adequate ventilation is achieved by opening windows or using a comfort ventilation system (CMV). On the other hand, windows that are not tightly sealed cause heat loss and draughts on cold days. These factors thus combine to create an unpleasant indoor climate and unnecessarily high heating costs.  

In you are retrofitting, it is advisable to have the new windows installed by a specialist, who will take care to remove any existing thermal bridges.

Mould growth is associated with elevated humidity levels and insufficient ventilation rather than with good insulation practice.

Indeed, the reverse is true: improved insulation quality prevents the formation of mould. This is found to be the case in many energy-efficient homes and buildings that have been retrofitted for energy efficiency. They are perfectly insulated, airtight and completely free of mould. If the external walls are not satisfactorily insulated, air moisture condenses in the cold areas, which favours the formation of mould. Effective thermal insulation of the façade tends to raise the surface temperature of the external wall and thus prevent moisture from accumulating.

It is likewise important to identify and eliminate all thermal bridges in the building (i.e. places where there are gaps in the insulation). Such bridges can be found, among other places, in recesses for radiators or on balconies. In addition, it is not advisable to place furniture in front of external walls, as this prevents the indoor air from circulating freely, meaning that the surfaces behind the furniture cool down.  
 

In the context of the building permit application procedure, it is necessary to respect the municipal planning regulations relating to setbacks from neighbouring private properties. The same provisions apply to constructions along the municipal public domain.

As is the case for buildings along the municipal public domain, buildings along the State road (national road and State-managed road) must, within the framework of the building permit application procedure, comply with the municipal urban planning regulations on setbacks.

For constructions located in the vicinity of the State public domain at a distance of 25 metres from a national road (N) or at a distance of 10 metres from a State-managed road (CR), established from the property line, a road permit is required from the Minister of Sustainable Development and Infrastructure. As part of a road permit, provisions regarding the setbacks of buildings in relation to the road will be applied. These may differ from the setbacks set by the municipalities.

With regard to building permits, the municipalities systematically check that buildings are set back from the municipal public domain or plot boundaries.

As a rule, the planning regulations for setbacks are regulated by the municipalities in their General Development Plan (Plan d’Aménagement Général, PAG) or in the Special Development Plans (Plans d’Aménagement Particulier, PAP).

For municipalities whose PAG has not yet been adapted to include current legislation, the planning regulations relating to setbacks are still included in the written part of the PAG or in the building regulations. For these municipalities, the measurement of setbacks in the event of energy retrofitting is set out individually, by municipality, in those documents.

On the other hand, for those municipalities whose PAGs have been completely revised since 2011, the Grand Ducal Regulation that is the basis for the applicable definitions provides that the building setbacks are to be measured without the additional insulating layer in the case of an energy retrofit.

In both cases, the municipalities can include derogation mechanisms in their regulations in order to promote energy retrofitting, for example through a reduction in the minimum setback to be observed.

Architects and consulting engineers, whose profession is defined by the law of 13 December 1989 organising the professions of architect and consulting engineer, as well as all experts approved by the Ministry of the Economy, can issue energy performance certificates

• Demolition: sale of a ruin or a building that does not have a heating installation and which will be demolished after purchase.
• Inheritance or gift.

• New building: any building that is subject to a building permit application. (A feasibility study concerning the use of renewable energies should be appended to the building permit application.)
• Extension of an existing building.
• Modification of an existing building (building permit required), if the surface area of the modified element of the thermal envelope exceeds the surface area of the same existing element (walls, windows, roof, etc.) by 10% and if the modification has an impact on the energy performance of the building. (Issuance of an energy performance certificate for the new planned situation.)
• Substantial alterations to an existing building (without a building permit), if the surface area of the altered element of the thermal envelope exceeds the surface area of the same existing element (walls, windows, roof, etc.) by 10% and if the alteration has an impact on the energy performance of the building. (Issuance of an energy performance certificate for the new planned situation.)
• Change of owner or tenant.
• Demolition: sale of a building that will be demolished after purchase, if the building has a heating installation, exterior walls and a roof.
• Modification of technical facilities, if the modifications of these technical facilities exceed €1,500 (for a single-family house) or €3,000 (for a multi-family house).