FAQ

In principle, the energy savings that can be accounted for by the obligated parties can be in any energy carrier, including fuels, oil, natural gas and electricity.

In principle, all energy consumers are affected, whether households, businesses or the public sector.

The implementation of this obligation mechanism was born out of the desire to achieve the objectives set out in the national energy policy on energy efficiency more effectively.

This measure allows the obligated parties to seize the opportunity to expand their business models and offer energy services to consumers. The experiences of other EU Member States that have already implemented such a mechanism have shown that this approach, based on sound regulation, makes possible the subsequent deployment of energy efficiency measures.

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.

The heat transmission coefficient (known as the U-value) determines how much heat passes through a building element – the lower the value, the better the insulation. Therefore, for example, a sand-lime brick wall with a thickness of 50 cm has a U-value of about 1.0 to 2.0 W/m² K. With an outer insulation thickness of 12 cm to 30 cm, the walls of well-renovated buildings today achieve U-values between 0.3 and 0.1 W/m² K.

Insulating materials are not all flammable. Building materials, and therefore also insulating materials, are divided into different fire protection categories. Moreover, a European standard regulates the classification of products and types of construction according to their fire behaviour.

This standard indicates that there are non-flammable insulating materials. Therefore, the main contractor can inquire about this beforehand, prior to deciding on the materials to be used. In principle, insulating materials made out of minerals are non-flammable. Mineral-based insulation materials are also covered by the Luxembourg Sustainability Certification for Housing (LENOZ) and can therefore be financed by the State as part of an overall project. Refits are also covered: the use of mineral-based insulation materials allows for higher financing than conventional materials.

Furthermore, there are other materials used as façade cladding elements that are flammable and these must be taken into account in this regard. This is why it is important to account for the overall make-up of the external wall in itself. Nonetheless, it may also include flame retardants (i.e. sealant, firewall, etc.) and thus provide protection against the spread of flames.

When improving building energy efficiency, insulation measures have the highest priority. No other measure can save as much energy for heating.

Several studies demonstrate that the production of insulation materials consumes much less energy than is saved later. Even with 30-centimetre thick insulation materials, such as polystyrene, the production energy required is already amortised after about three years.