In a net zero energy (NZE) facility, the roof is not just a leaky liability; it is an important source for energy savings and production. A project can utilize passive solar design, reflective roof surfaces, a green roof, skylights, and renewable energy generation. In a NZE design, the roof must contribute either extreme savings or generation. In particular, two uses of the roof space are directly tied to energy: skylights to reduce lighting energy and photovoltaics (PV) to produce renewable energy. However, when it comes to implementing these technologies in energy efficient or NZE projects, competition for roof space occurs.

A presentation by Gregory Raffio of Go Sustainable Energy highlights the importance of proper calculations in choosing a technology for the best utilization of roof space in a NZE building and presents the main factors. First, the presentation introduces the common energy efficiency technologies competing for roof space and their potential to contribute to NZE, but also their potential to conflict with one another. Next, the NZE path is chosen and a metric for NZE evaluation is introduced. Finally, sample scenarios for PV generation and skylight savings are analyzed and PV’s impact is favored. The findings demonstrate that, while PV reigns supreme in the roof space battle, successful integration of PV with surrounding technologies offers a project the best chance for NZE.


This year’s keynote speaker, Doug Kridler, is sponsored by The Columbus Foundation’s Green Funds.

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