Windows for renovation / refurbishment of existing buildings

What should I bear in mind? What is the ideal window?

Fenster für die Renovierung

EnEV: When modernizing existing buildings resulting in essential constructional modifications of parts of the building (facade, windows and roof), EnEV requirements (German Energy Saving Ordinance) apply. An exception from this rule does only apply if the area of the modified components affects no more than 10 per cent of the total building component area of the building (EnEV §9 Abs. 3). This means, if more than 10 per cent (of the total building area) is modified, EnEV applies and the maximum level of energy consumption of the building / flat must be observed. This means for windows that the U value must not exceed the limit of 1.3 W/m²K.

KfW: To obtain a loan from the German KfW development bank, a specified minimum level of energy efficiency must be observed. The German Energy Saving Ordinance (EnEV) serves as benchmark, but the level of funding rises if the building’s energy efficiency is considerably higher than stipulated by EnEV. In the field of window modernization it is important to make sure that these present a maximum U value of 0.95 W/m²K when realizing single measures funded by KfW. Additionally, walls shall have a better insulation value than windows to make sure that the window pane remains the coolest surface in the room. By this means potential condensation occurs on the window and not on the wall where it could favour mould growth. (For further info see

Passive house: Existing buildings refurbished to passive house standards are still relatively rare. However, the German government wants passive houses in the existing building stock to become the standard in the long and medium term. One of the major challenges will certainly be the individual constructional situation of the existing buildings, to which current products for renovation have to be adapted. aluplast is one of the first in the window sector to offer a window element of 70 mm profile depth certified by ift to meet the passive house standard.

Recommendations for renovation / refurbishment

  • energeto® 4000

    energeto® 4000

    The backstop gasket system energeto® 4000 with a profile depth of 70 mm is mostly used in the renovation sector and allures with smooth, filigree profile lines.   

  • energeto® 5000

    energeto® 5000

    The energeto® centre gasket system with a profile depth of 70 mm is irreplaceable especially in the renovation market.   

  • IDEAL 4000®

    IDEAL 4000®

    uPVC window with 70mm profile depth   

  • IDEAL 5000®

    IDEAL 5000®

    70mm profile depth for outstanding thermal insulation   


aluplast worldwide

aluplast weltweit


aluplast GmbH 

Auf der Breit 2
D-76227 Karlsruhe
Tel. +49 721 47171-0
Fax +49 721 47171-999


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aluplast worldwide

aluplast worldwide


aluplast GmbH
Auf der Breit 2
DE-76227 Karlsruhe
Tel. +49 (721) 47171-0
Fax +49 (721) 47171-999