The right windows can cut heating bills by up to 40 %. Here is how to pick the correct system for your home.
Why does the Uw value matter?
The Uw thermal transmittance coefficient shows how much heat escapes through the window. The lower the number, the better the insulation. For a continental climate aim for Uw ≤ 1.0 W/m²K.
Three key factors
- Double or triple glazing filled with argon.
- Five-chamber or larger profile with steel reinforcement.
- Three-seal EPDM gasket around the perimeter.
Quick system comparison
Schüco, Reynaers and Aluprof offer profiles with Uw between 0.71 and 1.1 W/m²K. The real spread between brands is usually under 8 %, but installation quality can swing performance by 20 %.
A poor install kills the best profile. Always check the installer follows the RAL method.
Estimated ROI
In a 90 m² apartment in Madrid, replacing class B PVC windows with class A+ pays back in 6–8 years at current gas prices.