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.

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.

The indicator I_eco12 represents the environmental impacts (I_env) and the impacts induced by the primary energy requirement (I_prim) of an insulation material, evaluated on an equivalent thickness of 12 cm. This results in an independent environmental assessment of the existing building, while taking into account the grey energy consumed by the insulation material.

To benefit from bonuses within the framework of aid for insulation measures in your home, the following criteria must be met:

• recycling of insulation materials: you can benefit from a 50% recycling bonus if at least 50% of your fossil or mineral insulation material is made from recycled raw materials. The 50% recycling bonus for fossil insulation materials is only valid until 31.12.2023.
• criteria for green insulation materials: you can receive a 50% FSC/PEFC/SFI bonus if your green insulation material is made from FSC/PEFC/SFI certified raw material