Defining Zero

It seems that many organizations are striving towards some form of zero-energy buildings. From code organizations (ASHRAE, IECC) to states (California, Massachusetts, Florida) to cities (Austin, TX) to non-profits (Architecture 2030) and even some future-thinking developers and designers (Zero-Energy Design, Sonoma Mountain Village), many are demanding, planning and implementing zero-energy building strategies now. Despite their admirable efforts, one thing and one thing only binds these groups together: the word "zero."

But how much is in a word? For these many different groups they all need a slightly different version of zero to make sense. A state or city can't (yet) really tell a home-owner that he needs to build in a sunny location to ensure enough solar power to offset his energy use. Similarly, a code cannot completely control what people put in their homes as well as how those homes are built. In other words, plug loads could easily tip the balance away from zero even in the most efficient home and the old realty adage still bears on this relatively new energy issue, location, location, location.

If you meet someone who has built a 'zero-energy home' you should ask her what she means. It's likely that each instance you get a different answer. Some people use gas for cooking and/or heating and others go all electric but end up spending a lot more on solar to break even. Some people consider zero to mean site energy or an electric meter that spins equally in both directions. Others determine they've reached the bottom by having no utility bills. If this weren't enough to confuse you, there is further the potential to have community-wide zero-energy. A developer could build clean power generation near the development to offset the energy use of each home, but the home-owners may or may not see the benefit.

There are simply not enough different terms to describe the many different 'zeros' we are going after. In an effort to make sense of this mess, putting on my state or national dictator hat, I would drop 'zero' altogether and go after a policy of Negative Load Growth (NLG). NLG would be the cumulative effect of deeply efficient mandatory new buildings, aggressive retrofits of existing buildings and incentives for nearly cost-effective renewable energy technology deployed wherever possible. If everything were pushed to the maximum the country would experience a decline in total energy use from buildings (including electricity and natural gas) thus a negative load growth. For more on the parts of this policy, see my blog on Promoting Energy Efficiency in Buildings.

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