How to control divide surface and offset curve on surface?

I followed this tutorial of OM. egvo on how to make Birds Nest Stadium and it worked like a charm.

But when I tried to make it work on a simpler, and more standard house-like volumes, it didn’t go so well.
1: If I input more than one surface, or facade if you like, it is unpredictable how it behaves.
2: How do I control what side of the surface a surface is offset to?
3: If I join the curves around a segment of the surface, how do I control what direction the offset goes, consistently?
4: If I split the surface into smaller parts, they behave differently regarding offset-direction, and the behave different if I bake the out and assign them for instance glass as material.

The basic question here, I guess, is how to control the direction of offsets, and normals of planes and curves - and how to treat several surfaces the same, without having to write the same code over and over.
Maybe I’m just rambling…

And the file, if anyone would like to give it a try.
divide and (24.3 KB)

Thanks! :slightly_smiling_face: