Green Roofs In Winter: Hot Design For A Cold Climate

“Everyone studies how green roofs operate in warm conditions,” says Brad Bass of the U of T Centre for Environment. “No one else has looked at winter design.” Bass analyzed a test roof built in Ottawa by Karen Liu of the National Research Council’s Institute for Research in Construction, to offer the first conclusive data that winter green roofs can help reduce heat loss and energy consumption during cold months. The results are currently on display in the Design For the Cold exhibition at the Chalmers Design Centre, Design Exchange.

The winter green roof uses evergreens – juniper shrubs – and a thicker soil base than typical leafy green roofs, which generally provide passive benefits to the environment by reducing the need for air conditioning on hot days. The winter roof was installed on both a standard test house and an energy-efficient winterized house. Bass used environmental systems performance software to chart the indoor temperature fluctuations in both buildings.

“The results for the winterized house were good, and the results for the regular house were dramatic,” says Bass. “The assessment opens up designers to considering winter roofs as part of a year-round energy efficiency strategy.” A poster illustrating the research will be on display until Nov. 27 at the Design Exchange, 234 Bay St. The University of Toronto Health Care, Technology and Place Program is also one of the partners presenting the exhibition, which called for planners, designers, artists and health researchers to design new ways for Canadians to thrive in cold winters.

The winter green roof project was funded by Environment Canada, the National Research Council, the University of Toronto, the Office of Energy Research and Development (Natural Resources Canada) and the Climate Change Action Fund.