Defining ZNE – Not as Easy as You think!

As more projects are pursuing zero net energy, the details of defining ZNE are becoming more critical, and trickier.  Are we achieving net zero in terms of kilowatt hours or cost of energy?  Will the metric be time dependant modeled energy performance or a full year of actual data?  Is natural gas ‘allowed’ in a ZNE project if it is offset? 

These questions and more were discussed at a special “Defining ZNE” workshop that I was fortunate to attend last month in San Francisco.  The workshop was set up because the State of California, in consultation with a variety of non-profit organizations, is working to define ZNE ahead of the scheduled code cycles requiring ZNE for all new residential buildings by 2020 and all new commercial buildings by 2030.

Although we didn’t come to “the answer,” here are some observations so far:

-   Predicted performance, based on modeling prior to construction, will likely be the California standard instead of actual performance based on occupancy.  Modeling will align with current Title 24 protocol and will standardize variables based on occupants (e.g., 1 homeowner who just reads all day vs. a family of 4 with lots of electronics).

-   Gas and propane will likely be allowed with a calculated offset.  Although we see many of our ZNE clients going all electric, allowing for some gas will provide a good transition for renovations and special applications in new construction.

-   Outside organizations will continue to raise the bar.  The Living Building Challenge, for example, does require a full year of occupancy to certify under their ZNE program, which has been providing some great data as we all move in this direction.

All in all, the fact that we have arrived to this level of detail is a great sign of how achievable ZNE really is.  While the jury is out on details of implementation, we are full speed ahead on making ZNE happen!