A research team has determined that the color and type of rooftop on your home can have a big impact on its environmental performance. The researchers compared three rooftop technologies, from manufacture to end of use, as well as with a variety of environmental impacts.
Researchers from the Schulich School of Engineering, Calgary, Alberta, Canada point out that sustainable roofing technologies, including green roofs, white roofs, and solar photovoltaic panels can have significant environmental benefits, but research and studies of these technologies usually look at their use and benefits in hot climates.
Because a full analysis of their environmental impact, especially their use in colder climates has never been done, it was decided that a comparison of the three rooftops be studied in Canada’s colder climate.
“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.”
The following types of roofs were examined in the study:
* White roofs – A roof tiled or painted white to reflect the sun and heat.
* Green roofs – Rooftops covered in vegetation and a growing medium.
* Photovoltaic roof – Solar panels that generate electricity.
Comparing energy performance
The analysis of the three technologies covered every aspect of the life of each type of roof, from the manufacture, transporting, actual installation, and energy use. Three areas of Canada were used to make the energy performance analysis, Vancouver, Toronto and Calgary using two software programs.
One program, called Energy Plus, is a building simulation software. The other, Simapro, is a life cycle database that simulates the movement of the different roof types from manufacture, transportation, and construction.
The researchers determined that Canadian weather does not like “white roofs.” The researchers say that white roofs scored a big negative on environmental impact, and the authors of the report do not recommend the use of these types of roofs in Canada.
Green roofs, on the other hand, have a number of good points, and reduce heating and cooling energy use, as has been shown in other studies. But their environmental impact does not stand up to the use of photovoltaic cells.
The winner, hands down, are photovoltaic rooftops. This is surprisingly stated in the opening statement in the report; Photovoltaic rooftop technology “demonstrates the highest environmental performance in all impact categories considered … and is the preferred option from an environmental perspective.”
Dr. Bergerson says, “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. Our study builds on the existing knowledge of rooftop technologies and provides recommendations directly relevant for our context.”
The study was published in the Journal of Industrial Ecology on April 6, 2015 under the title: “Sustainability of Rooftop Technologies in Cold Climates: Comparative Life Cycle Assessment of White Roofs, Green Roofs, and Photovoltaic Panels.”
