Green Roofs and Vertical Gardens. What are they and what are their benefits?

Last updated on October 23rd, 2023 at 08:16 pm

Recently we talked about an initiative to install green roofs on buses that brought multiple benefits to the city and its citizens. Well, today we are going to discuss in more detail the subject of green roofs: green roofs and walls. We will see what benefits they bring and what materials and species are being experimented with to make green roofs and vertical gardens last longer, ensuring the sustainability and functions of the structure with minimal maintenance.

What are green roofs?

Green roofs are a construction formed by a continuous substrate on which plant species grow on a relatively large surface.

Green Roofs and Vertical Gardens. What are they and what are their benefits?

They can be developed both horizontally (green roofs or green roofs) and vertically (vertical gardens, green walls, vertical gardens…).

Green Roofs and Vertical Gardens. What are they and what are their benefits?
Vertical gardens in Shanghai’s Bund

To build green roofs it is necessary to take into account a series of questions such as:

  • Its location. Where it is going to receive more light, or more precipitation…
  • Its dimensions. What surface of the building it is going to house, what form it is going to have…
  • Its materials. What species it will house, what substrate will support these species and what materials will support both the substrate and the plants to keep the building protected from possible water leaks.
  • As a whole, these materials have the objective of making these green roofs last over time, which is why research on them has not stopped for years…

Objectives and benefits of green roofs

Green roofs are a construction, but mainly they are an essential element of urban naturation. 

Green Roofs and Vertical Gardens. What are they and what are their benefits?
Vertical garden on the terrace of the Westfield shopping center, London.

They are built with the aim of beautifying, naturalizing and purifying the urban environment through the species they house.

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But the benefits of green roofs and vertical gardens are not only a mere aesthetic effect derived from seeing the plants hanging or on a building. In addition, green roofs and vertical gardens have other benefits:

  • They capture CO2 from the surroundings. Gases from cars, chimney emissions etc… Producing O2 through its photosynthetic function. A 1m2 canopy captures 50 g/CO2 per day, producing the oxygen that a person needs for a year (Darlington, 2001).
  • They insulate thermally. By receiving the sun’s radiation, the building that houses it saves energy both for heating in winter (the roof stores the heat) and cooling in summer (the roof retains the heat and does not pass into the building). Vegetable roofs are thus an excellent natural insulator; a 1m2 roof can retain up to 5ºC. This effect also translates to the whole city, cooling it in summer and mitigating the heat that can be given off by the asphalt.
  • They insulate acoustically. This insulating function also translates to the sound level, a 1m2 cover can insulate about 11 db, which is appreciated in areas of night bustle.
  • They favor the biodiversity of the environment. A multitude of insects and birds hang around the green roofs as they provide them with a refuge in the city, which favors the spontaneous appearance of local species.
  • They improve the citizen’s perception. According to psychological studies, green roofs improve the perception of the environment by human beings, which increases their mood, makes them more positive and more relaxed.
Green Roofs and Vertical Gardens. What are they and what are their benefits?

Materials for green roofs

As I mentioned before, green roofs are a constructive element, an element of urban naturation that has multiple objectives and that is built with very specific materials to ensure that they last over time.

This makes a lot of sense, since if we are thinking of naturalizing the environment, it makes sense to establish a structure that is sustainable and has a minimum maintenance. It does not make sense to create a structure with an extra cost for the city, since, no matter how many benefits it may bring, this would not be sustainable if it entails other high costs.

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Thus, both the plant species chosen and the substrates that support them have been the subject of study for many years.

I have been fortunate to visit centers such as EL ENCÍN, of IMIDRA, to learn a little more about these new materials for green roofs. These new materials allow the structures to last over time. They will undoubtedly help vertical gardens and green roofs to consolidate in the not too distant future as another element of the city.

Green Roofs and Vertical Gardens. What are they and what are their benefits?
Experimental vegetation cover. El Encín Farm.

I comment a little above what materials are being worked with:

Substrates: The key to the support for the plants that house the groundcovers lies here, in the substrate. The substrates of the plant covers are mainly hydroponic substrates. These substrates retain moisture better, so the canopies are irrigated only with the local rainfall itself. This hydroponic substrate has the novelty of containing 0 % of peat, something very important since peat is a scarce natural resource that is already being used a lot in all the industrial substrates that we buy for our orchard or garden.

If we are talking about naturalizing the environment, what sense does it make to extract a natural resource from it to bring it inside the city…?

On this basis, several studies have been made with mixtures of substrates (coconut fiber, composted remains, pine bark, etc.) to know their behavior over time and their ability to support different species among other parameters …

The conclusions are very varied, but I can tell you that plant covers are established without any problem with mixtures that do not harbor any peat, which in the long run are free of parasites and fungi, are stable and maintain their fertility. Although their total lifespan has not yet been determined.

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As for the species that are cultivated, I have not collected so much information, but I can tell you that they are looking for species with a good vegetative surface (to capture as much CO2 and solar radiation as possible), which have a minimum maintenance and an ornamental or decorative character. To give you some examples are the: Teucrium chamaedrys, Othonna cheirifolia and several varieties of the genus Sedum as indicator plants during the elaboration of the studies.

Green Roofs and Vertical Gardens. What are they and what are their benefits?
Here we see the species used to evaluate the quality of substrates over time.

As a conclusion of all this, I can tell you that green roofs are evolving day by day, with new substrates and species that guarantee their perpetuity in time and their function of urban naturation. I personally try to achieve a hybrid structure between cover and urban garden, with species that have a minimum maintenance and offer the possibility of being harvested periodically for human consumption.

I’ll let you know how it goes, we are working on it 😀.

If you have photos of other green roofs or vertical gardens that catch your attention, do not hesitate to attach your photos in the comments below. Best regards!

Author

  • James Jones

    Meet James Jones, a passionate gardening writer whose words bloom with the wisdom of an experienced horticulturist. With a deep-rooted love for all things green, James has dedicated his life to sharing the art and science of gardening with the world. James's words have found their way into countless publications, and his gardening insights have inspired a new generation of green thumbs. His commitment to sustainability and environmental stewardship shines through in every article he crafts.

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