9 January 2026
Windows for Energy-Efficient and Passive Houses – Which Parameters Really Matter?
Why Windows Are Crucial in Energy-Efficient Buildings
In modern residential construction, windows play a key role in the overall energy performance of a building. They influence not only daylight access, but also heat losses, solar gains and indoor thermal comfort.
In energy-efficient and passive houses, poorly selected windows can significantly reduce the benefits of even the best wall and roof insulation.
Key Parameters of Energy-Efficient Windows
Thermal Transmittance (Uw Value)
The most important parameter is the Uw value, which describes heat transfer through the entire window (frame + glazing).
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Energy-efficient house: Uw ≤ 0.9 W/m²K
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Passive house: Uw ≤ 0.8 W/m²K
The lower the Uw value, the better the insulation and energy efficiency.
Glazing Units
Modern energy-efficient windows typically use:
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triple glazing,
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low-emissivity (Low-E) coatings,
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noble gas filling (argon or krypton).
These solutions reduce heat loss in winter and improve thermal comfort during summer.
Window Profiles
Equally important is the window frame system:
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multi-chamber PVC profiles,
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aluminium profiles with thermal breaks,
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sufficient installation depth (usually 80–90 mm or more).
Window Installation – Performance Depends on It
Even the best windows will not perform properly without correct installation. In energy-efficient buildings, airtight and thermally optimized installation is essential to prevent thermal bridges.
Are Energy-Efficient Windows Worth the Investment?
Yes. High-quality windows provide:
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lower heating costs,
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stable indoor temperatures,
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improved living comfort,
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increased property value.
FAQ
Is every triple-glazed window energy-efficient?
No. Performance depends on the entire system: glazing, frame, spacers and installation.
Are large glazed areas suitable for passive houses?
Yes, if Uw values and building orientation are properly planned.
