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I'd look for somewhere with old farm buildings then put a new build on as the main accommodation.
TBF, the accommodation bit is less important in terms of how energy efficient it is (although I would hope to power it mostly through solar/battery). The brewery is where I really want to be as 'off grid' as possible and, since it'll be a brewery, it'll need to be really clean too, so new build (probably metal) will be more important. Old farm buildings might look great and be plentiful, but if you stick a brewery in them, you're going to struggle to make a beer that isn't infected with something or other.
Ideally, I'll find an old place that's got enough land to build on and isn't in too dilapidated a state. Might be asking too much, but we'll see. My cousin's a qualified carpenter who's built his own place out in Brittany, so I'm gonna be drafting him in to help out (he doesn't know this yet).
Not to derail, but I'd look for somewhere with old farm buildings then put a new build on as the main accommodation. There are always plenty of old properties in France for sale due to the way inheritance is mandated and the fact that almost no young people want old houses.