It looks ordinary enough:
However, this is as far-out a building as you’ll ever likely to see. The green coating isn’t paint, it’s algae behind glass in a thin
exothermic [Update] bioreactor.
The circuit includes biogas extraction and of course the algae eat carbon dioxide, so the building – with other less ostentatious tweaks – is claimed to be completely carbon-neutral.
Hamburg is cool and wet, so buildings need heating almost all of the year. The technology will therefore never take off in Haight-Ashbury or the liberal bits of Beverly Hills. [Update: this speculation retracted below in comments] But there’s nothing to stop Barack Obama from building himself a carbon-neutral slime palace retreat in Maine or Minnesota. And how about the Governor’s mansion in Alaska?