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 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 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 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: