There are a variety of ways to make your building more sustainable and energy efficient, but the most discussed area to improve is the roof. For years, we've heard about the benefits of white roofs, green roofs and roofs covered in solar panels, but depending on the building and where it's located, one of these types may make a bigger impact than another.
For building owners in hot, dry climates, turning your roof white is one of the easiest and cheapest things you can do to dramatically cut your energy use, but what about buildings in colder climates? Which choice produces the most benefit?
A study recently published in the Journal of Industrial Ecology details a full life cycle assessment of each roof type for buildings located in Vancouver, Toronto and Calgary, Canada and comes up with a clear winner.The study specifically modeled office buildings with a large roof of 1,340 square meters, assuming a 50-year life span for the building, and declared solar roofs the definite winner with green roofs coming in second and white roofs last.
The study didn't just look at the energy efficiency gains the roofs produced, but the full environmental impact of manufacturing, transporting and installing the materials as well as any toxic chemicals used in the process and how the roofs affected human health, air, and water quality.
White roofs performed the poorest for cold climates because although they reduce cooling requirements in hot weather and also add to the life span of the building, they actually increased the heating requirements in colder climates during the longer cold weather stretches.
Green roofs performed much better by both lowering cooling needs and heating needs, improving air quality and reducing storm water runoff, but in the end solar roofs had the greater impact.
The on-site electricity generation of solar roofs offsets the negative emissions from their manufacture and transportation and the continued use over years ends up being a major positive by reducing the amount of coal-powered electricity a building uses. The panels reflect heat in the hotter months to reduce cooler, though the reflection does slightly increase heating needs in colder months.
You can read more specifics about how the different roofs performed in the full life cycle assessment here.