Williams Engineering is a company that has emphasized sustainability from its start. Overlooking Edmonton’s river valley, its headquarters also boasts a healthy and sustainable green roof system.

Installed in June, 2010, the beautiful rooftop meadow on the Williams Engineering Building is a rare green roof success story in the harsh climate of Northern Alberta. Designed as part of ongoing research through the Northern Alberta Institute of Technology (NAIT), the retrofit project aims to test which plants will be most resilient in Edmonton’s dry and windy rooftop environments.

The retrofit proved especially challenging because of structural limitations of the existing roof. As a result, growth media depths vary across the entire roof, with 3-4” areas in the centre and 6-8” areas along the edges of the roof.

For the different growth media depths, Bioroof prescribed two colorful native urban meadow mixes. Selected species include golden aster, prairie cinquefoil, blue flax, coreopsis, black-eyed Susans, low golden rod, and various native grasses and fescues. Bioroof’s Eco-System utilized locally sourced ingredients to create their Eco-Blend growth media, in order to ideally suit the plantings and the environment. This high organic blend growth media was necessary to providing essential nutrients and unparalleled water holding capacity for the meadow species to surpass all expectations and flourish in such harsh climatic conditions.

The retrofit also included thirteen 2’ x 8’ research test plots which were designed by NAIT to test growth media at depths of 3” (75 mm), 4” (100 mm), and 6” (150 mm). For the test plots, Dr. Leonie Nadeau, a retired NAIT senior, led a team of students from NAIT’s Technology Management and Landscape Architectural Technology programs, along with a group from H.P. Wagner High School. Students were involved in both research design and investigation. The best performance results were expectedly seen in plants in the deepest growth medium.

The Alberta Real Estate Foundation provided initial funding, while Native Plant Producers Society of Alberta donated 1,500 seedlings that included 17 species of grasses and forbs.