FAQ

Since 1 January 2017, every new construction of a residential building in Luxembourg must be a Nearly Zero Energy Building (NZEB) in terms of energy consumption. As a rule, the NZEB corresponds to the AAA energy classes. However, certain conditions relating to the construction location may cause variations in these energy classes.

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).

The energy performance certificate is a regulatory obligation, therefore no subsidy is provided for its establishment.
The energy performance certificate is issued according to precise rules set out in the amended Grand Ducal Regulation of 30 November 2007 on the energy performance of residential buildings. It is valid for 10 years from the day of its issue. The issuance of an energy performance certificate and the information it contains shall not result in any direct obligation for energy retrofitting.

The energy performance certificate (EPC) or energy passport is the quality label that defines the energy performance of a residential building. The certificate provides information on the energy efficiency of residential buildings and thus allows comparisons to be made with other residential buildings. Thus, even without technical knowledge, the consumer can assess the energy quality of a residential building.

In principle, a wall does not breathe. Air renewal and moisture removal are only achieved by ventilation (via windows or a mechanical ventilation system). The effect of 'breathing' as mentioned above refers to the transfer of moisture by the diffusion of water vapour. In practice, this is minimal and does not play any role in the removal of moisture. On the other hand, it is important for interior plaster to be able to absorb moisture from the air and release it back into the interior after ventilation. The moisture regulation effect therefore only operates within the first few centimetres (on the interior side) of a wall. For example, clay plaster on internal walls provides excellent moisture regulation.

It is often façade insulation systems that are implicated and pilloried for this. It is true that on insulated walls the outer render layer has a lower temperature and slows down the drying of rainwater and condensed water. However, in order to determine the origin of the spread of micro-organisms, various factors have to be taken into consideration: weathering, orientation, proximity of trees or bushes and the lack of protection provided by protruding building elements (roof overhang, window sill, projection, eaves, etc.).

For new builds, weather protection should ideally be provided from the outset. Similarly, by opting for a thicker finishing coat, higher surface temperatures can be obtained.

On the contrary! Poor quality sealing can result in significant amounts of energy loss. However, the risk of building deterioration is an even greater factor: in winter, warm, moist air escapes to the outside through leaky areas such as joints and cracks. In this way, the air cools down and moisture condenses, which can lead to the formation of mould in the cavities. In most cases, we don't even notice it and therefore we can't react.

Airtightness is therefore a key issue. You must ensure that your house is well ventilated, either simply by opening the windows or by installing a controlled ventilation system.