Is tree height on private properties regulated by ordinances?

Nothing has happened so far, but that doesn't mean anything. Two of that kind also fell over behind the property last year. Moreover, to my knowledge, even the neighbor's insurance would not be responsible in case of any damage.

Ha, you are funny! Why would anyone cut down their trees just because you want to build a house in the neighborhood? On the contrary, the neighbor could demand that you make sure his trees are not damaged when the heavy construction vehicles arrive.

They are far enough away. Besides, I didn't expect him to cut down the trees because of our house construction. The trees affect him much more than they do us.

Not to mention all the debris that will constantly clog his roof drainage.

They are far enough away. Besides, I didn't expect him to cut down the trees because of our house construction. The trees bother him much more than they do us.

Not to mention all the dirt that will constantly clog his roof drainage.

But that is his problem, not yours

Why should the insurance not be responsible?! Of course, it would be liable, since damage to third parties would have been caused by their property. A relatively recent WOG definitely covers that...

What else I notice:

"The property owner allegedly really wants to preserve the trees"

...tells me that you haven’t even spoken to the lady personally yet. From my own experience, I can advise you: do that first. We had a similar situation, a neighbor’s tree 7 meters directly on the boundary, objection period long expired (here in BW also 5 years), the previous owner should have raised a finger. The neighbors didn’t want to cut down the tree or respond to our arguments, we were upset, after a few weeks and another chance conversation it turned out: they didn’t want to fell it because they didn’t trust themselves... our suggestion: we take care of felling, a forester friend does it, we give him a crate of beer, they give him pizza... --> tree gone, everyone happy.