You can't rebuild without destroying what's there. They did assessments, ran trials, picked different architectural designs, and decided which could be transitioned into green energy efficiencies, and those that couldn't. With Ukraine, they decided much of the infrastructure was to old, and ownership issues would be to complicated to track having gone from multiple different owners. Germany has built an industry based on new green technologies, which is why they are in Russian occupied areas of Ukraine, providing services to them to rebuild. All you have to do is read the global partnership agreements and their agreements of mutual understanding to find this all out. If they went to people and said it would be too cost prohibitive to transition all your housing into energy efficiency so we are going to relocate everybody and tear down entire sections of cities, one, people would be outraged, two, it would be time consuming holding meetings and getting input, three, it would be cost prohibitive to do it that way. The better way is like what they are doing in Ukraine and Gaza, just bomb the hell out of it.