Coincidentally, this morning we learn of a project in the UK where a huge1911 woolen mill, built the same year as the launch of the Titanic is being converted into condos, and that the building well be completely carbon free. "All Titanic Mill’s heat and a high proportion of its electricity will come from a Combined Heat and Power unit, or CHP. This will be fuelled using various species of tree cuttings, chipped to create a biomass fuel. The sustainably-managed trees undergo a regular period of growth each year, allowing wood to be harvested in a continual cycle. During the growth process the trees extract CO2 from the atmosphere in sufficient volumes to balance the CO2 which is released when wood is used as fuel." It also has 400 KW square metres of photovoltaics and rainwater harvesting.
Unfortunately this mill appears to be in the middle of nowhere near the town of Huddersfield, and the site plan shows it surrounded by a sea of parking, so while the building may be carbon neutral its residents probably won't be. ::Titanic Mill via ::Observer