I've also actually renovated my old place. I did it because I didn't want to rebuild the place entirely (there was no need, it was woven brick, more solid than most bunkers), and because I would have had to agree with the neigbors, which was ... let's politely call it "not guaranteed".

But very quickly it became clear why that was the right decision: building codes. People legislate building codes, but of course they're unwilling to DO anything. So old buildings, built against old building codes, don't have to change, and that means they effectively get to ignore building codes. If I rebuilt the place I would have had to move the house (as in physically move it, just 4 meters, but it's a house, 4 meters might as well be 400 kilometers, you have to rebuild it). I would have to give up at least 40% of the surface area (the "ground surface") AND one of the floors. Net result: the new house would have been about half the living surface of the old one.em.

So obviously the renovated house is worth a lot more than a new house: for starters it's double the size!

It's even self defeating: the isolation of the old house is better. Yes, people legislate modern isolation materials but if the house MUST be a lot smaller there must be a lot more contact area with the cold air, because it wouldn't be built against the neighbor's house anymore and a LOT less thermal mass (thermal mass = free heating, more or less) so you're starting from a very bad starting position.