Canadian Architect

Feature

Greener Pastures

A Survey Of Green Roofs In Several Nordic Countries Debunks Some Of The Myths About Successfully Adopting Such Technology For A Wide Range Of Projects In Canada.

January 1, 2009
by TEXT Kerry Ross PHOTOS Kerry Ross, unless otherwise noted

It is a centuries-old idea wrapped in new technology that offers efficiency and beauty. It will even contribute towards LEED certification, but green roofs remain a hard sell in parts of Canada despite the increasing number of projects in Southern Ontario and on the Pacific West Coast–where one can find research and demonstration facilities, municipal incentives and organizations advocating for public awareness. Meanwhile, across the Prairies and in Canada’s North, there is still a false perception that green roofs won’t work.

There will always be resistance to new technology, but in colder Canadian climates there appear to be more myths and fears about green roofs than in other countries. Not only are potential clients worried about leaky roofs, initial up-front costs and long-term maintenance, but others question their relevancy, given our long, cold winters.

One of Alberta’s pioneering green-roof projects (with apologies to the sod roofs that were commonplace among settlers) can be found on top of the Bison Courtyard in Banff. Initiated in 2000, the mixed-use commercial and residential project was led by green-roof guru, William McDonough (with the Zeidler Partnership of Calgary). McDonough has long espoused the benefits of green roofs–superior stormwater management, cleaner air, improved energy efficiency and occupant comfort, and the provision of habitat for urban species.

But municipal authorities in Banff were unconvinced. In an effort to explain the vision of inviting nature into the buildings and emulating the mountain experience, Peter Poole of Arctos & Bird Enterprises built a demonstration plot on the roof of the existing building on Bear Street and gathered everyone to see the power of blending ecology and aesthetics. The town officials immediately understood what Poole was after, and the Bison Courtyard went ahead, complete with green roofs.

Every gardener on the Prairies knows that it takes a lot of effort to make things grow. The winters are long and cold, the growing season is brief and there is little precipitation. An additional challenge in Southern Alberta is the Chinook wind. Understandably, when presented with the concept of a green roof, clients are reluctant to embrace the technology for fear that it is impractical at worst, difficult at best. They want to see proof beforehand.

Enter my Nordic experience. Northern Europe has been sprouting green roofs for decades. Surely, learning first-hand from their experiences would help overcome some of the obstacles to planning, designing, and building a green roof on the Canadian prairie and other cold climates.

From my initial exposure to green roofs on top of the Bison Courtyard project, I was anxious to learn more. To benefit from the European industry that is at least 30 years ahead of the Canadian one, in August 2007 I began my study, touring over 35 green roofs across Iceland, Denmark, Norway and Sweden. The experience allowed me to compare the many objectives and methodologies of Nordic versus Canadian green roofs.

The physical geography felt familiar, as did the sense of being part of a relatively small population living on the northern fringe of larger, more powerful neighbours like Russia. However, the cultural geography of our two regions is much different. Most visible, from my perspective, was the broadly held reverence for and knowledge of design, craft and architecture shared by all four Nordic countries. This is hardly surprising, given that early on in their formal education, young people in many of the Nordic countries receive schooling with a strong emphasis on art and design. These countries are also being guided by a strong ecological imperative, having adopted and advanced the United Nations’ Agenda 21–a blueprint for sustainable development. It was, after all, a Norwegian, Dr. Gro Harlem Brundtand, who led the UN commission that defined the term “sustainable development” in 1987. At about the same time, pioneers in the sustainability movement such as the Natural Step and Greenspace Factor began operating in Sweden. Denmark–with only limited natural resources, save abundant wind energy–has shown the world how resourceful thinking and good design can power a country and energize an economy. Iceland has also become a world renewable energy leader, using its abundant geothermal resource to power and heat its homes as well as developing an extensive greenhouse-based agriculture.

Clearly, there was much I could learn from this Nordic brand of forward thinking and, as I toured these countries over the course of a month, three clear themes seemed to emerge: the green roof as building amenity; the green roof as building ecology; and the green roof as building culture. These trends seemed to be underpinned by the following broad concepts:

Adaptation and Resilience

While the regions I visited are considerably milder than Alberta, they have their own climate challenges. Iceland, for example, does not suffer the extreme cold temperatures we do but their average temperature over the year is much cooler. Buildings are often set into the site to shelter against the elements. Historical ones frequently have turf walls and roofs for added insulating value.

Context and Continuity

In Iceland and Norway, green roofs, with the exception of those using modern waterproof membranes, have continuity with the turf roofs of the past. In Denmark, green roofs are driven by a pragmatic need to make density more attractive and are included as part of the designer’s tool palette. In Sweden, green roofs are driv en by formally adopted ecological benchmarks and are acknowledged as a significant green space or low-impact development strategy.

Cost

In Iceland and Norway, traditional grass or “turf” roofs are considered to be one of the most economical roofing choices. One reason they are less expensive choices is that they use locally available material. Conversely, Denmark and Sweden are closer to a diversity of green-roof suppliers in Scandinavia as well as elsewhere in Europe.

Overall, green-roof projects in Europe enjoy significant cost advantages over Canadian ones. Because Europe is a far more mature industry, there is more competition and infrastructure, and therefore lower costs. In Alberta, a green roof can still cost twice as much as a conventional membrane roof, which is a major concern for owners and developers. Transportation costs of systems and materials in Canada can add up to 25 percent or more to the cost of a new green roof. But over time and as the industry grows, these costs will come down and the longer-term cost benefits of green roofs will become even more attractive.

This cost reduction has already occurred in the European industry over the last three decades. I saw first-hand evidence of many successful green-roof applications, allowing me to return to Canada armed with more than a few details about how to emulate that success here.

One of my most significant experiences occurred as I was standing atop Bella Hus by schmidt hammer lassen architects in the new restad district of Copenhagen. I was awestruck by the panorama around me, and the meadow beneath my feet. The rich foliage was from a sedum-rt-grsvegetation or a “sedum-herb-grass” mat that uses a mix of perennial grasses and flowering forbs with sedums. The mat provides immediate coverage, excellent cold and drought tolerance, and great biodiversity. It is a product that is not yet available in North America. The knowledge contained in seed plantings can be found in other projects around Scandinavia as well. One stormy afternoon in Vislanda, Sweden at the Veg Tech AB production field and head office of Scandinavia’s largest green-roof provider, I was introduced to a blend of hardy species of seed that had been harvested in Siberia and nurtured to create a pre-cultivated mat that excels in northern climes. In general, there is a Sc
andinavian sensibility, especially in Iceland and Norway, to let things be without too much concern over maintaining the landscape. Unlike Canadians, they are not concerned about making a green roof manicured. They just want to make it natural.

During my research, I felt as though the greening of Europe’s roofs was part of a quiet revolu tion. My hunch was confirmed by a report recently presented at the World Green Roof Congress in London. Tobias Emilsen of the Swedish University of Agricultural Sciences completed a comprehensive inventory of green roofs in Malm, Sweden–from those found on top of garden sheds to large-scale projects like the 9,000-square-metre, mainly residential redevelopment of the Augustenborg district. Emilsen concluded that there are many more green roofs being built than people realize.

While there have always been turf roofs at higher latitudes (and elevations), a few contemporary green roofs have begun to appear in the far North. For example, there is a green roof just 25 kilometres south of the Arctic Circle and minutes away from Norway’s second-largest glacier in the town of Mo i Rana. There are also new green roofs on the facilities surrounding the Ice Hotel in Jukkasjrvi, Sweden (6750′ N). And currently under construction in Hamary, Norway (at 6806’11” N) is the highly anticipated Knut Hamsun Museum, designed by Steven Holl Architects. It too will be capped with a “Norwegian sod roof in a modern way.”1

It is exactly the awareness–or lack thereof– that has been an obstacle to the greening of Canadian cold-climate roofs. Anyone trying to get a green roof built in Canada has experienced first hand the resistance to “new” technology. But there is the demonstrated benefit and success of green roofs near the Arctic Circle and elsewhere in Nordic countries. These efforts in establishing green roofs in colder climates can only help foster and nurture our own green-roof movement so that it too can thrive in rather than merely survive our long Canadian winters. CA

Kerry Ross toured Nordic green roofs in August 2007 with the assistance of the Burwell Coon Travel Scholarship from the Royal Architectural Institute of Canada and a leave of absence from her employer, IBI Group in Calgary. She is a cofounder of the Alberta Ecoroof Initiative.

1 Arctic Circle Project by Steven Holl Architects. For more information, please visit www.e-architect.co.uk/norway/knut_hamsun_center.htm

———

Augustenborg Botanical Gardens

The Augustenborg Botanical Gardens, situated in Malm, Sweden, is home to the Scandinavian Green Roof Association and provides nearly 90,00 square metres of research and demonstration green-roof projects. Extensive systems are employed along with pre-grown and in-situ applications. An interpretive centre has been built to accommodate the abundant number of tour groups that go through the facility.

Helgolandsgade 6 Housing Renovation

Designed by b19 architekten of Germany, the Helgolandsgade Housing Renovation converted a decommissioned school into 16 housing units in the gentrified neighbourhood of Vesterbro, located in central Copenhagen. The upper roof was converted into a 140-square-metre common amenity space, which includes an outdoor kitchen, dining and lounging areas. The project incorporates a series of sedum mats along the length of the west side of the roof which was installed in a matter of hours. The mats create a landscaped edge to the common roof deck. The lower sloped roofs of the service building are also covered in sedum mats.

Veg Tech AB

Veg Tech AB is the leading green-roof manufacturer in Scandinavia with over 40,000 square metres installed in various projects. Located in the village of Vislanda in Southern Sweden, the company headquarters are divided into field production operations, head offices and a nursery. While sedum mats are their best-selling products, Veg Tech also produces systems for stream-bed rehabilitation, stormwater mitigation and green-screen hedging material.

Bella Hus

Designed by schmidt hammer lassen architects near the centre of Copenhagen, the Bella Centre is a four-to seven-storey complex of 63 rental apartments. Completed in 2007, there is a common roof deck with a barbeque and lounging area atop the seventh floor. An herb and sedum mat, consisting of a mixture of perennial grasses and flowering forbs, was installed to provide coverage that resembles a meadow. This green-roof system provides excellent immediate coverage, excellent cold and drought tolerance as well as greater biodiversity.

Reykjavk City Hall

Designed by Studio Granda, Reykjavk City Hall consists of two three-storey structures at the north end of Lake Tjornin. The building, which opened in 1992, has a living iridescent wall on its north-facing exterior. The lush, green vegetation grows on a dark black, lava-clad wall, creating a stark contrast. This stunning vertical surface is reflected in an adjacent shallow pool. Much of Iceland is covered in lava fields and the wall replicates the moss and lichen that grow over these fields and cover much of the island. An automated irrigation system keeps the lava surface constantly moist, promoting the growth of mosses, ferns and lichens.

Solheimer Eco-Village

Craft and building are evident in the totems carved with Icelandic runes (characters from the alphabet) which are displayed in the grassy meadow leading up to Sesseljuhus.

rbr Outdoor Museum

The Icelandic turf roof has evolved over 11 centuries where numerous examples of these and other historical green or turf roofs are present at various open-air folk museums in the Nordic countries. A scarcity of building materials combined with Iceland’s isolation from Europe and other markets meant turf became the principal building material in Iceland. It was local to the area and in ready supply. Iceland has unique settlements of rural turf farmsteads comprising several one-storey, one-room buildings in a row with a central adjoining corridor and gabled faades enclosing walls of turf or stone. The turf roofs were often constructed with a birch-bark layer for water shedding and two to three layers of turf dug from the adjacent surroundings with specialized hand tools. They would often be weighted down with stones to prevent the turf from lifting off with the wind.

Kastrup Peak Load Plant

Designed by the Danish architecture firm of Gottlieb Paludan a/s, this earth-sheltered half-dome building is situated near Copenhagen International Airport. At 1,135 square metres, it’s one of the largest green-roof applications in Scandinavia. The building houses a system of pumps, pipelines and heat exchangers as well as a peak load and backup heating plant to supply power to the nearby airport and surrounding districts. The green roof consists of moss and sedum mats placed on top of a felt drainage layer and waterproof membrane. The mats were delivered in 10- metre-long rolls held off the boom of a crane and installed one next to another with an overlapping flap. Opened in 2006, the project has won numerous design awards and demonstrates that an industrial building need not be an unsightly structure.




Print this page

Related Posts







Have your say:

Your email address will not be published. Required fields are marked *

*