ZinCo Canada’s Jelle Vonk talks about the advantages of green roofing for condominium communities and the environmental impacts green roofs can have on surrounding hardscapes!

As our cities continue to grow, those involved including designers, planners, and governing officials, all wish them to be beautiful, dynamic, and friendly places for the people that live in them. However, simultaneously we must ensure our urban environments are sympathetic to the natural environment we are a part of. Less black and grey, more green and blue!

Green roofs are an important part of greening the urban environment in cities and the reasons why are easy to understand. Conventional roofs are black and sterile – places of unnatural extremes. And they are wide-spread, covering many thousands of hectares in a typical city. Green roofs take that space and convert it into a place of hospitality for plants and wildlife. Where plants grow, animals which can use them for food and shelter will follow. Not as extreme as a rain forest, but certainly a simple ecosystem can function to add extra space, beauty and provide a home to wildlife. When well-designed, a simple ecosystem can grow and increase in complexity as time goes on providing ongoing important benefits. How long? When well designed, the roof can last for the life of the building that supports it (over 100 years and counting) as numerous examples in Europe amply demonstrate.

What are the benefits of a green roof? There is a reasonably long list that has been the driving force for the implementation of green roofs, first in Europe in the 1980’s and now throughout the world. To begin with, green roofs absorb and hold large volumes of water. Even very shallow (7 – 10 cm) green roofs will hold about 40% of the annual precipitation and green roofs with deep ‘soils’ will retain 90 – 100%. In cities plagued with old and failing infrastructure and very limited budgets to fix the problem, anything that reduces the volume of runoff water is welcomed. The water retention capabilities of green roofs were a driving force for their implementation in the city of Toronto.

A number of other benefits accrue as a direct result of the water captured on green roofs. For example, the evaporation of the captured water has a cooling effect, which reduces the building temperature and surrounding city temperature. The process of water evaporation can be direct evaporation, like clothes left on a wash line to dry, or indirectly, through the plants on the roof, which is called evapotranspiration. Water needs energy to evaporate, that is the key, and this energy comes from the sun and the surrounding environment. Thus, evaporation on a green roof has a cooling effect, reducing overall temperatures. This can directly affect the air conditioning needs of a condominium community and additionally, lowers the temperature around the building helping to keep the city cooler, reducing what we call the “urban heat island.”

Another popular benefit of a green roof is the long lasting water proofing. Many conventional roofs have water proofing on the outside, which means it is exposed to the elements and the sun. The water proofing on a green roof lasts longer because it is protected under the greenery. How much longer will these membranes last? No one really knows; the best evidence comes from Europe, where the oldest green roofs built using modern technology are still fully intact 30 – 40 years after installation.


Additionally, green roofs absorb significant amounts of sound because they are made up of a plant canopy and layers of loose sound absorbing materials in their build-up. This benefit can be useful for condominium buildings located near intensely noisy areas such as airports, large highways or a downtown core.

In addition to the above benefits, green roofs contain a significant wildlife advantage. As mentioned, where there are plants, the rest of the food chain will follow. By controlling the green roof design and construction, specific species of plants or habitats can be targeted. This is actively being done on many sites in both North America and Europe, where green roofs are designed to increase the habitat space for targeted birds or insects and to encourage greater biodiversity in the urban landscape. Numerous studies have shown that green roofs often become an important means of expanding the habitats for threatened or endangered species. While this has often happened accidentally in the past, there is a new thrust to use green roofs to improve biodiversity in the city. This overtly biological approach to green roofs has a more ecological focus, however, still retains the benefits mentioned earlier; storm water retention, improved energy budget of a given building, etc.

The final benefit to consider is how green roofs can improve the urban environment for humans. After all, it seems reasonable to say that the urban environment is created by us for us. Unfortunately, in too many cases it has been poorly done – a situation we are all too familiar with. There is a growing body of evidence which demonstrates that we humans are hard wired to need the natural environment. We are biophilic and need to be in contact with nature. That contact is known to increase happiness and reduce stress, which ironically often plagues those living in high stress environments such as highly urbanized areas. Green roofs open up a stronger possibility of interaction with the natural environment within cities and urban cores. There is no additional real estate required and with proper planning, the available space will allow for almost unlimited opportunities. These roofs can be used for recreational spaces, parks, gardens, wild life habitats and even urban farming, which has been quickly increasing in popularity in recent years. The benefits of this new green space would not only add a communal space for the residents of a given condominium community but would likely add monetary value to the property.

In view of the benefits outlined above, the most intelligent and informed management practice when designing and building for our future is to reap the aggregate benefit of green roofs through the implementation of such on all available spaces. Although alternative solutions exist for each of the problems outlined above, such as adding increased insulation to a roof to decrease energy usage in a condominium building, they do nothing to reduce storm water build up, reduce “urban heat island,” improve the lifespan of the waterproofing, develop urban biodiversity and so much more.

In the past, the full benefits that can be acquired by green roofs in the GTA have not been achieved due to regulatory restrictions; however, recently the new Toronto green roof by-law, which mandates green roofs on new buildings, has come into place. With the new by-law in place, it would be wise for the regulators, design community, and developers to adopt a more inclusive approach to the integration of green roofs from the start of each project located in an urban space. Not only will this provide financial benefits for the unit owners but it will impact the changes in our environment over the generations to come. It is important to remember that to reap the full and long term benefits of a green roof, reliable technology and a professional design, construction and maintenance team must be consulted.

This permanently reliable ZinCo Green Roof Assembly consists of the following functional layers: protection mat, drainage layer, filter sheet, growing medium and plants.

This permanently reliable ZinCo Green Roof Assembly consists of the following functional layers: protection mat, drainage layer, filter sheet, growing medium and plants.

* If interested in investigating green roof conversion prices or acquiring further details, please speak to your property manager and/or Board of Directors. A green roof would be deemed a significant change and would require a special meeting where the approval of the residents (66 2/3%) would be secured. The installation of a green roof would be a Reserve Fund expenditure.