A Closer Look at One of the Oldest Green Roofs in North America

By Karen L. Edwards, RCS Editor.

Scheduled for demolition after 22 years, the green roof provided a unique chance to study its performance. 

The Mountain Equipment Co-op (MEC) in Toronto installed a green roof in 1998 that was considered revolutionary at the time. For years, the roof was a testament to green roof technology and was visited by thousands during its lifespan. When the building was set for demolition to make room for new development, it provided a unique opportunity to test the performance and longevity of the system 20 years later.

Roxanne Miller, SOPREMA Canada landscape architect, writes in Living Architecture Monitor Magazine that they were able to gain access to the roof in 2019 and perform cut tests on two different parts of the roof. They took a sample from the green roof and one from another part of the roof that was exposed to the elements with the goal of answering the question of whether a green roof can prolong the life of the waterproofing membrane.

The system installed on the roof in 1998 was SOPRANATURE® green roofing system by SOPREMA. The SOPRANATURE system was designed to protect the membrane from physical and thermal damage. The thinking is that because it isn’t exposed to the elements and UV rays in particular that the life of the membrane would be extended. Miller’s team wanted to find the answer to that question with the 12” x 12” samples taken in the cut tests.

A Gel Permeation Chromatography (GPC) testing machine was used to evaluate the samples. The same testing was performed on a new SBS membrane as well for comparative purposes. The results were impressive. The study found that the green roof clearly protected the waterproofing membrane beneath it. The testers said, “While it is not possible to give a precise estimate on the extended life expectancy of the waterproofing, to say that it doubles it seems to be a very timid assumption since after 22 years, the covered sample was almost exactly the same as a new SBS modified bitumen membrane.”

The study proved the benefits that green roofs bring to protecting the waterproofing membrane and may lead the way for even more green roofs being installed in the future.

Growing in popularity

This is a photo of the roof of the 909 Walnut Fidelity Tower in Kansas City, Missouri. A landmark on the National Register of Historic Places, the 909 Walnut Fidelity Tower Building has been refurbished to provide 34 floors of beautiful, spacious luxury suites for high-rise living. Connecting the 909 Walnut Tower and the 929 Walnut building is a new eight-story parking garage with a lush garden that provides an outdoor and community space typically only found at a nearby park. This rooftop garden is yet another example of the vegetated roofs that are popping up throughout Kansas City.

“They act as a great insulator, reduce storm run-off, dampen noise and can even lengthen the life of the roof,” said Jeffrey Bruce. Jeffery L. Bruce & Company was responsible for the design of the rooftop garden and is a local landscape architecture firm and national leader in green roof design.

To see detailed testing information and what plants were on the roof in Canada, read the full article. Learn more about SOPREMA in their RCS Directory.