Their architectural and environmental concept is genius and it would be great to see them more often
Switzerland, France and other European countries are passing laws requiring new commercial and residential buildings to have at least partially green roofs. In Canada they have been a beautiful fact for decades, in Australia green roof spaces are also multiplying, although there is no law for this.
Covering roofs with earth and planting natural greenery in it has been a practice in Norway since 1890. This is how Scandinavians protect roof structures from rotting and thus strengthen their houses. In the early 20th century, Norwegians migrated to North America and brought this sustainable idea to the United States. In our country, green roofs are also increasing, but not at such a pace and scale as we would like. The architectural, ecological and aesthetic concept of roof gardens is amazing and it would be wonderful to occupy a larger part of the urban landscape.
Green roofs control temperature, reduce air and noise pollution (because the combination of soil and plants absorb and deflect sound waves), support urban biodiversity by becoming a home for birds and insects, but they are also very beautiful.
Everyone dreams of contemplating nature more often, resting and working in peace among greenery, and how nice it would be if they could do all this on the roof they live on! Besides being pleasing to the eye, green gardens on the tops of buildings have other important advantages.
1. The "heat island" effect
This phrase explains what happens when a building begins to absorb heat from the sun thanks to the plants planted on its roof. They significantly reduce the harmful effects of the sun’s ultraviolet rays because the sun warms concrete and asphalt faster than plants and trees.
Under green roofs in big cities, the heat can decrease significantly, according to a study by Canadian scientists. They found that in spring and summer temperatures under a conventional roof reach up to 45 degrees, while under green roofs there are fluctuations of about 6 degrees.
This is because, through the daily evaporation cycle, plants cool the overall air temperature in the surrounding space. This saves energy during the warmer months by reducing the need to buy and run an air conditioner, providing shade and coolness.
2. Energy efficiency
Lower energy consumption in residential cooperatives with roof gardens can save 3 to 10 percent on fuel bills, according to a German energy efficiency study. That’s because roof gardens are great insulation for any building – losing around 30% less heat in winter and keeping it pleasantly cool in summer. Increased thermal resistance saves heating and cooling costs for the entire building.
3. Long life for buildings
Fact: In the city of Roanoke, Virginia, they installed a garden on the roof of the municipal building and it extended its life by 20 to 60 years. The explanation: exposed to sun, rain and wind, roofs change, contracting in colder weather and expanding when it gets hot.
Temperature amplitudes shorten the life of the roof and the entire building, but the roof gardens store the available energy and this slows down the destructive processes – keeping the building healthy for longer. This reduces the need to maintain and replace materials that, in turn, also require energy to produce.
4. Fresh air
The dirty air in industrial cities contains many harmful gases, such as the chemical compound carbon dioxide, but roof gardens can reduce its harmful effects – natural greenery absorbs it, releases oxygen and thus contributes to the fight against global warming.
Filtering air from pollutants thanks to plants reduces the spread of dust, reduces smog and, accordingly, greenhouse gas emissions in the atmosphere of urban centers. Leaf surfaces capture about 85% of the dust particles in the air and contribute significantly to the reduction of sulfur dioxide and nitric acid in the air we breathe. To achieve this better air quality, however, a few green roofs are not enough.
5. Storm water control
Roof gardens absorb up to 75% of rainfall in the warm months and around 40% in the winter season and thus drastically reduce the flow of rainwater. Depending on its design, a green roof reduces rainwater runoff by between 50 and 90% and thus supports sewage systems. Plants are also a natural filter for the water that runs off, but they also reduce the runoff itself. This reduces the risks of flooding in cities – an especially important fact as torrential rains increase due to climate change.
6. Urban agriculture
Rain is water and energy that we get for free from the environment – why not make the most of this gift?! Roof gardens offer a great chance for this because rainwater waters the vegetation, but can also be collected for later use. This makes it very easy for another environmental initiative to flourish: the growing of vegetables and fruits on the roof.
This is not a utopia at all – in Montreal and Toronto, for example, it is normal and common for people to make organic farms on their roofs. These farms are tiny but produce fresh and organic food. Growing your own crops saves money, but also eliminates the danger of consuming vegetables and fruits with pesticides and microbes.