Over the last year, I covered four separate symposia at the New York Academy of Sciences on "Zero Net Energy Buildings." The final installment was just posted. (If you're not an NYAS member, you can see my story and view the presentations by going through the NYAS link, under the "Clips" tab, at my website, http://www.DonMonroe.info.)
Something like 2/5 of the energy in the U.S. is used for buildings--more than for transportation. The zero net energy building vision is that by combining serious energy conservation measures with on-site generation (often photovoltaic, but also including wind and other sources) an individual building can put just as much energy back onto the grid as it takes off, over the course of a year.
One critical aspect of the definition is determining what's included in "the building." Does it include photovoltaics over the parking lot? Firewood grown in the back? I did not understand why the building should be the right level of granularity, rather than, say, the block or the city. (Obviously zero-net energy rooms would be too fine-grained.)
Part of the reasoning is that transmission is expensive, and that cost can be avoided with local generation. But most of the buildings under discussion meet the zero-net-energy goal only over time, achieving the goal only because of easy transfer of electricity to and from the grid. And some generation methods clearly have economies of scale (take nuclear, for the sake of argument) that make them most effective at a larger scale than a single building. Perhaps the most compelling reason to focus on the building level is that this is where a single team of architects, engineers, owners, and so forth can work together to make the needed decisions.
The challenges are great, not least because there are so many inefficient buildings out there already. Many retrofits that will pay for themselves over time, even discounting future savings. Unfortunately, decision makers are often short-sighted, and need to learn how to value sustainable investments, including the growing desirability of "green" properties for tenants.
Nonetheless, stabilizing global carbon levels could require reductions in the ballpark of 75%, and simulations by The World Business Council for Sustainable Development indicate that market forces alone won't get there, even with onerous carbon taxes. This coalition of sustainability-oriented corporations advocates serious government intervention, on top of carbon pricing, as critical to reducing carbon fast enough to lessen global warming.