Michael R. Davis, a Buildings & Grounds guest blogger for August, is a principal in the architecture firm Bergmeyer Associates. He is also an adjunct faculty member and a member of the Board of Overseers at the Boston Architectural College.
 Michael R. Davis |
About a year ago, the governor of Massachusetts convened a task force of “experts” to recommend how the state could jump-start an idea about high-performance building called net-zero-energy building. But the term “experts” is in quotation marks because, going into the meetings, barely a handful of us on the task force had any experience in net-zero-energy building, and those who did were largely working on single-family homes. We all learned a lot.
So what are net-zero-energy buildings, and why are they important?
A net-zero-energy building is a building that, over time, will produce as much energy as it needs, or more. That’s the basic definition. For our task force, an important corollary was that all the power a net-zero-energy building draws from the grid or produces itself must be from renewable sources.
Further definition by negation: A net-zero-energy building is not off the grid. There will be times when a net-zero-energy building will need to buy power. But to be net-zero, there will also be times when the net-zero-energy building will sell power back to the grid. A net-zero-energy building is not necessarily a carbon-neutral building. To be really, truly carbon-neutral, a building must also offset the carbon emissions caused by the fabrication of its components, like the windows and mechanical equipment. This is nearly impossible to achieve one building at a time. We’re coming to understand that carbon-neutral is a good goal for a state or a city or corporation or a university or a profession, but for an individual building you have to say, “Well, we’re just talking about carbon-neutral operations”—which is essentially the net-zero-energy approach.
Net-zero-energy building excludes a lot of the other concepts that are important to sustainable design, like life-cycle costing, recycled-content materials, improved indoor air quality, and so on. But we know a good deal about those subjects. How buildings perform against energy targets is the aspect of sustainable design that is the most important in light of climate change—and the one that we understand the least as practitioners. That’s why net-zero-energy building is so important.
Finally, a distinction between the four different “flavors” of net-zero-energy building: net-zero carbon, net-zero cost, net-zero source and net-zero site.
Net-zero carbon we’ve touched on. Only igloos and tepees are carbon neutral. Tree houses are close. Net-zero cost is agnostic as to the power source. If I built a small coal-fired power plant attached to my building and generated more power than I had to buy I could come out net-zero on cost but not be environmentally responsible. Net-zero source asks to balance a building’s power needs as generated at its source. The source-energy multiplier for electricity can be three or four times what a building’s electric meter reads due to transmission losses, and source energy is also agnostic on emissions. So net-zero site is the concept for us: A building that supplies its own (net) (renewable) power needs. —Michael R. Davis
Find other Buildings & Grounds guest-blogger posts in our guest-blogger archive.
Follow Buildings & Grounds through your favorite RSS reader: