How Useful Are Sustainable Rooftops In Colder Climates?

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A new study has investigated the usefulness of sustainable rooftop technologies — such as rooftop solar, white roofs, green roofs, etc — in colder climates, such as Canada.

“Sustainable rooftop technologies,” write the publishers of the journal, “can provide great environmental benefits, but studies of these technologies often look only at their use in hot climates and do not assess their full environmental consequences.”

The journal article, published in Wiley’s Journal of Industrial Ecology, compares these rooftop technologies in the cold Canadian climate, rather than in more stereotypical southern-climes.

“Environmental performance of building technologies is very dependent on climate conditions. Therefore, conclusions from technology assessments elsewhere were not necessarily valid in cold climates such as Canada,” said Dr. Joule Bergerson, senior author of the study. “Our study builds on the existing knowledge of rooftop technologies and provides recommendations directly relevant for our context.”

Beyond simply ascertaining whether a particular technology works well in the cold, the study also aims to evaluate the environmental performance of a technology on a life cycle basis.

Interestingly, and highlighted in the study’s opening summary, rooftop solar PV “demonstrates the highest environmental performance in all impact categories considered … and is the preferred option from an environmental perspective.”

Green roofs, or as I like to call them, hobbit roofs, yielded unsurprisingly beneficial environmental impacts, however these impacts were “much less significant than those obtained with PV.” Green roofs do reduce both heating and cooling energy use, as has been seen in many studies previously.

Canadian weather, however, does not appear to be a big fan of white roofs, with this particular technology rewarding a net negative environmental impact, leading the authors of the report to not recommend this particular technology in cold climates.