FAQ

Calculation of the environmental indicators is directly linked to calculation of the thermal transmittance U and its inherent calculation rules. However, the layers of membranes and seals, which are negligible when calculating the thermal transmission coefficient given their low impact in terms of their insulation capacity, should be taken into consideration for calculation of the predicted environmental indicators.

For a new building, the construction elements of the thermal envelope (= external structure) as well as internal walls and slabs are taken into account.

For the elements of the external structure, all the layers taken into consideration for calculation of the U value are also taken into consideration for calculation of the I _env and I_prim indicators.

Party walls and partition walls between different units in a block of flats should be considered internal walls (within the building envelope).

For existing buildings, only new insulating materials used during the retrofitting works are taken into consideration.

For existing buildings, only the primary energy requirement of the technical installations for conditioning the building should be considered for the I_prim indicator (Chapter 4.2). The primary energy expenditure of the existing building is not taken into account. 

In general, the environmental indicators I_env and I_prim are calculated automatically (from the database implemented in the Lux-Eeb-H software) when filling in the calculation sheet for the thermal transmission coefficients of the different layers making up the thermal envelope (U value).

Section 7.3 of the Annex to the Grand Ducal Regulation on housing sustainability certification uses the I_env indicator for different constructions. Current data on building materials, recorded in the LuxEeB-H software, can be viewed in the Materialdaten LENOZ 2016 document on the website http://www.ml.public.lu/fr/lenoz/Experts/index.html.  

A LENOZ certificate can be issued for all residential buildings with an energy passport, whether they are new or existing residential buildings. Issuance of the certificate is associated with Class 4 "minimum sustainability" (Chapter 0.2 of the Annex to the Grand Ducal Regulation on housing sustainability certification). Existing residential buildings can achieve this "minimum sustainability" by means of comprehensive retrofitting works.

In general, all costs relating to the works necessary for the installation of insulation are considered eligible costs. A detailed list of the works considered is available from the Environmental Administration.

An application for an agreement in principle must be submitted by the applicant before the start of any energy retrofitting work. If the applicant changes the retrofitting concept on the advice of the energy adviser, after the agreement in principle has been reached, the applicant may submit an application for a new agreement in principle. This request is optional. If the applicant wishes to ensure that the modified retrofitting concept remains eligible, it is essential that they submit a new application for an agreement in principle.

The values of the I_eco12 indicator are provided for some commonly used insulation materials in Chapter 7.3 of the Annex to the Grand Ducal Regulation on the Certification of the Sustainability of Housing and can be reused.

In the event that other insulation materials are used, experts can calculate the I_eco12 indicator using the I_calc calculator, which can be viewed online 

The I_eco12 indicator is used to assess new insulation installed on an existing building and is taken into consideration in the following cases:

• in the case of sustainable energy retrofitting of elements of the thermal building envelope under the Klimabonus subsidy scheme;
• as part of the LENOZ certification of an existing retrofitted building.