Insulate the cavity between the window and the masonry!

Good morning,

to get straight to the point, how do I best insulate the cavity and with what? I have looked into the WDVS panels, or should I just put in Sturodur panels and foam it up? I argued with the window installer because I had a different opinion, and now I’m facing the problem and would like to fix it myself if possible. The window installer had only foamed it below and said it would be fine like that…. According to him: use mineral wool and stuff it until everything is sealed—I did not want to accept that at all….

Best regards
goubi

This has to be airtight. Foaming is nonsense. It is generally botched work, what I see in the picture.

In my opinion, it needs to be lined with bricks. And then sealed cleanly.

We build with 36.5cm Poroton bricks filled with mineral wool. Cutting them is not easy because the brick breaks very quickly. I had also considered the idea of building it up, but would it be possible to fill the entire cavity with Mauerrandstreifen so that everything is airtight? They are easy to cut. That was my thought, I just wanted to ask what you think about it.

You can also fill the gap with regular unfilled perforated bricks or even better Ytong.

With Ytong, you have the advantage that the stone has no hollow chambers and is easy to cut.

For sealing, mounting foam and compressible tape. That's how I would do it.

What speaks against filling the gap with wall edge strips (Styrodur boards)? I mention it because I still have plenty in stock. Additionally, foam every smallest opening and stick the compressible tape below the window.

Basically nothing. Maybe the very poor sound insulation? It would feel somehow too unstable to me, even though I have often used styrodur.