The windows were delivered yesterday. The window installer noticed that one window was 10 cm narrower than needed. He said it was his fault, he could order a new one (it would probably take 14 days+ again) or install this one. On the left edge, he wants to put Styrodur in between, which insulates very well.
Basically, I don't want to wait that long since all the upcoming work (electricity, gas, plumbing) will not be done until after ALL the windows and doors are installed.
Is it safe to use Styrodur, or can it cause cold bridges and mold? After all, it is also used to insulate all sorts of concrete parts.
The masonry is 36.5 Poroton bricks. And this is a new building, the roof truss is just finished.
In our case, two windows were damaged and therefore not installed. It took several weeks. The OSB boards were just installed there for such a long time.
And if you look at the whole life period, two weeks is nothing. Do you really want to compromise because of that?
There are aerated concrete boards that are exactly 5 cm thick, one on each side, and that's it.
When building a house, 2 weeks is nothing! If a locked building is absolutely necessary in your next trades, close it with OSB for as long as possible.
Re-order it, install it, done.
If it has to be tight those 2 weeks: take 2 formwork boards, nail them to the masonry outside, cover with foil so you can do other work.