Overhead and Underfoot: Building a green roof upside down.

The Green Roof atop the Vancouver Convention Centre (West building)

by Jen Pennington

photos by Robert J. Pennington

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On a recent tour of the largest living green roof in North America atop the Vancouver, B.C. Convention Centre, one can’t help but be awed. The tour organized by Dow Chemical Company as part of Globe 2010 was a rare glimpse into the dichotomy of what you see vs. what you can’t see. Designed by LMN Architects, the building is the world’s first LEED Platinum convention center. It’s about taking in something visually and understanding at a deeper level that natural beauty and the creation of new wildlife habitats in urban settings can successfully coexist with the right mix of landscape architecture, engineering, and construction. The fact that one can easily take for granted the man-made materials underneath an organic surface is a testament to its success.

Sedums on the Green Roff over the Vancouver Convention Center

Brilliantly colored sedums looking towards the water

As you step out the doors onto the first level, one is struck by the brilliant red, orange and pink beauty of native sedums blooming in spring amidst a precisely placed irrigation system. Bruce Hemstock, Landscape Architect for PWL Partnership explains that the irrigation system utilizes black water from the convention center and desalination machinery to water the plants making it a very sustainable system. The vast expanse of this orderly growth is amazing and you can’t even see the grasses above yet. Walking along the sloped path that leads to the green areas of the main roofs, one passes by the apiary of bees that help pollinate the area. As you step up to the grassy rise of the roof you are instantly transported to a park in the sky. It is so large at six acres that you never feel as if you are on an actual roof, and therein is the real beauty of it. Now in its second year of growth, the illusion is so surreal in an urban environment that it’s easy to disregard what lies beneath the top layer.

Roof layers and substrate display at Dow's both at Globe 2010.

Digging down into what makes the roof so unique is the fact that the layers that go into a normal roofing system are inverted. As Mike Kontranowski, the Strategic Market Director, Architectural Markets for Dow Building Solutions explains, “It’s turning the roof upside down.” In this case, 2.5 million board feet of Styrofoam™ brand insulation and more than 500,000 board feet of Styrofoam™ Highload insulation from Dow sits directly on top of the roof. On top of that lies a series of other substrates, and protective barriers before the placement of soil and the thousands of indigenous plants and that grow there. With the addition of all these materials, the lightest weight component, keeping the roof thermally stable, reducing weight load,  and enhancing energy efficiency at the base is the Styrofoam™. A dimpled water barrier on top of that prevents water from seeping through and also holds droplets of water to retain moisture in the soil.

The roof is truly inspiring with its many levels of beauty and sustainable attributes. As green roofs become more popular in cities, my hope is that those in the design, building and materials industries share this knowledge readily. Not just amongst the largest architecture firms and contractors but down to the small business levels of builders and designers in outlying areas or smaller cities where adoption is slower to manifest. If we are truly concerned about creating eco communities and championing environmental and energy efficiency benefits, the challenge for all is how to inspire change broadly while making it affordable to install in the first place.

All photos copyright 2010 Robert J. Pennington.