It's true that the Duflot law on thermal renovation is targeted at individual owners, whereas, clearly, it's at the level of an apartment building that the biggest gains can be made.

I think this will require regulatory constraints as well as subsidies, and French proprietors don't take too kindly to that sort of thing.

For the use of artesian water, surely that needs to be done on the level of district heating? Messing with the groundwater at the level of individual buildings in an urban environment doesn't sound like an excellent plan to me.

_{It is rightly acknowledged that people of faith have no monopoly of virtue - Queen Elizabeth II}