Green roofs: A growing trend!
Since their arrival in Montréal in the mid-2000s, green roofs (or living roofs) have multiplied by the hundreds in the city. Inspired by the principles of sustainable urban planning, these increasingly popular installations offer a unique aesthetic, as well as numerous benefits for their owners. An overview.
Improved air quality, reduced urban heat island effect, improved rainwater management, longer life of the roof membrane, increased resistance to fire, energy savings: green roofs provide considerable benefits when properly designed and maintained.
First, plants used in the composition of the green roof act as filters and capture volatile particles, contributing to the absorption of air pollutants and to healthier air. In addition, green roofs can retain up to 75% of rainwater, reducing the risk of sewer backflow, erosion, flooding and contamination of drinking water.
Then there’s comfort. You’ve probably noticed how the pavement and asphalt absorb heat in the summer. Roof vegetation decreases this effect, making way for a more temperate and pleasant environment. With proper installation, plants and substrates also protect your roof against UV rays and erosion, in addition to slowing down the spread of a possible fire. Lastly, roof vegetation provides better thermal insulation, minimizing winter heat loss and air conditioning requirements during the summer season.
Consult professionals for your project
Would you like a green roof? Be aware that the construction of a green roof requires compliance with many steps and criteria governed by la régie du bâtiment du Québec. The purpose of these measures is to avoid structural failure of your property and the deterioration of existing materials. We strongly recommend that you call a landscape architect or an expert horticulturist to determine which plants can adapt to roof vegetation in order to undertake your project in accordance with existing regulations.
Standards to be considered range from the structure of your home to the choice of materials and selected plants, as well as from the layout of your roof to its annual maintenance. Overall, a green roof system includes a series of components installed on your building’s sealing system: vegetation, a growth substrate (at least 100 mm), a filtering component, a drainage layer, a water retention system and an anti-root barrier.
What is a growth substrate? Quite simply, a mixture of aggregates and organic matter. The growth substrate should never be replaced with garden soil. Moreover, you must select your plants wisely. They must be low in height, wind resistant and adaptable to the extreme seasons of our Québec climate, but also to the thickness of the substrate. Good to know, right?
In addition, to facilitate drainage to the roof gutters, define circulation passages for maintenance and prevent the spread of fire (in the event of a fire), vegetation-free areas with incombustible materials (stone, gravel, concrete slabs) should be included in your design.
Finally, there are three types of green roofs: extensive (with a growth substrate up to 150 mm), semi-intensive (growth substrate with a thickness between 150 mm and 300 mm) and intensive (growth substrate exceeding 300 mm). Which one to choose for your particular property? That’s precisely the type of question you will ask a specialist when planning your project.
Properties of the future
Conscious about the environment, architects around the world are increasingly planning the integration of green roofs in the design of residential and commercial projects. As one of the ten most advanced cities in North America, Montréal stands out for installations on the Quebecor head office building and Collège Rosemont.
Green roofs: the latest trend or construction direction of tomorrow? The future will tell!
Want to see more? Take a look at these beautiful green roof projects around the world.
Happy summer!
Blog image: source.
