Windows in new buildings

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

EnEV: Buildings to be constructed are to be designed in such a way that the maximum levels of transmission heat loss stipulated by the applicable EnEV (German Energy Saving Ordinance) are not exceeded. However, an upper limit for windows has not been defined specifically. Nevertheless, a U value (thermal transfer coefficient) of 1.3 W/m²K for windows as presented by the reference building described in EnEV has established itself as maximum.

KfW: The German KfW development bank with its loan programs strives for an even higher level of energy efficiency than stipulated by the applicable EnEV. For buildings to be constructed that comply with KfW requirements, certain funding, e.g. by low-interest loans, is possible. Basically, these loan programmes have replaced former state subsidy for owner-occupied homes and demand for KfW funding is rising constantly (see

Passive house: Passive houses are buildings that can do without conventional heating; they are heated passively by solar energy entering e.g. through large windows especially on the building’s south side. Windows on the north side are either small or there are no windows at all to minimize heat loss. Solar gains on this side of the building are usually negligible. There are different regulations for the construction of window elements for passive houses that apply. KfW for example only requires a maximum Uw value of 0.8 W/m²K to grant funding, while the Passivhaus Institut Dr. Feist lays down requirements on single components, which generally increases the price of window elements. The German institute for window technology ift recently published a guideline for passive house windows requiring nearly the mean value of the above mentioned and by this means presents a reasonable benchmark for future constructions. Window fabricators should pay close attention to the requirements stipulated in the invitation to tender as the building components must meet these specific requirements regardless of other standards that might be met.

Zero-energy house: These houses consume even less energy than passive houses; under normal use, they consume at most as much energy as they produce.

Energy-plus house: Above all, manufacturers of prefabricated houses offer energy-plus buildings that produce even more energy than they consume under normal usage. The extra energy can for example be fed into the power grid. In terms of thermal insulation, the construction of this type of building is based on the passive house principle. Additionally, it is provided with sophisticated technologies (photovoltaic systems etc.) to generate electricity.

Product recommendations

  • 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.   

  • energeto® 8000

    energeto® 8000

    energeto® 8000 with a profile depth of 85 mm is specially designed for the new construction segment and convinces with top insulation values. The 85 mm system in Classic-line design with its clear straight lines is a real eye-catcher and, with an unparalleled Uf value of 0.94 W/m²K, an exemplary energy saver.   

  • IDEAL 4000®

    IDEAL 4000®

    uPVC window with 70mm profile depth   

  • IDEAL 5000®

    IDEAL 5000®

    70mm profile depth for outstanding thermal insulation   

  • IDEAL 8000®

    IDEAL 8000®

    85mm profile depth - energetically and visually at the highest level   


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