Building 2400 sq ft (with the extra consumption a second structure entails) to "replace" 2700 of already existing/ functioning housing is wasteful. It most certainly isn't "green". There are three such "green" tech homes near us; the average build cost was close to 600/sq ft. This is "green" only in a monetary sense to the architect and builder. With energy costs at ridiculously low rates, and slated to continue so because of global energy discoveries, spending vast quantities on these innovations is irresponsible. The batteries, electronic equipment, plastics, and high-tech pieces are toxic to source and produce. Further, inserting a cottage next to your neighbors' backyards is invasive: gardens should be quiet, peaceful places--- and many such have become businesses, i.e. Airbnb. How many neighbors will enjoy having a motel next to them?
Lastly, a wise architect once said that the greenest home is a beautiful one: it will endure.
A garish, ultra-expensive craftsman? A folly, at best.