D.
D. Specific elements
1) Window frames
Paradoxically, frames are generally more energy-efficient than required by current standards in Belgium! NBN EN 1026 distinguishes between 4 levels of airtightness for the sections of lab-tested frames. There are however two comments to be made here: •
stipulating Level 4 (i.e. the highest level of wind-proofing) is not always sufficient in a project aiming to achieve n50 = 0.6 vol/h;
•
the majority of frames available on the Belgian market are much better!
This is why the CSTC has proposed introducing Levels 5 & 6.
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