Net-Zero-Energy Buildings – Do we get it all wrong?

By Oliver Baumann, President

There’s a common theme among many of the most prominent and publicized net-zero-energy buildings in the United States: they’re largely defined by significant Photovoltaic (PV) integration. In fact, many of these projects achieve net-zero operation only after additional PV has been installed! Is a PV-first strategy the best way to realize the intentions behind net-zero-energy building practice?

I recently peer-reviewed a paper about lessons learned from a net-zero energy project in North America. In the abstract, the author preached the importance of an integrated design approach to achieve high performance buildings. To my disappointment, the only “integrated” approach involved was predicting the size of the PV system required for the building to achieve net-zero – based on a benchmark from comparable buildings. The paper concluded that the completed building ultimately didn’t demonstrate a net-zero energy operation. Furthermore, thermal comfort requirements were met only 85% of the time in the building core and 73% in the building perimeter. I’m concluding that the occupants are uncomfortable for 15% and 27% of the time!

In my opinion, presentations and publications about net-zero energy buildings far too often focus on the contribution of renewable energy production, rather than increasing the energy efficiency. That same paper that I reviewed misinterpreted the definition of a net-zero energy building as one “[…] that produces at least as much energy from renewable sources as it uses in a year.” This is a small but significant departure from what the cited sources (ASHRAE, NBI, and others) say: they all stress the increasing energy efficiency first and addressing the remaining needs with renewable energy sources second.

Come on A/E/C industry, we can do much better! We all know “Reduce, Reuse, Recycle” – we can apply similar lessons here. EURIMA’s Trias Energetica describes the natural loading order for high-performance building design:

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