A Detailed Look at the Green Roofs and their Types


What can you see in an aerial view of the top-most urban cities? Well, I am sure you are going to see the swathes of black tar and asphalt rooftops. Do you think they are looking good? If your answer is yes, then I would argue that you haven’t seen the green roofs from the sky. I won’t say only the looks of the buildings matter. It’s about various other factors too. Your dark roofs would radiate the heat off of it. In order to tackle this issue and many others, a new trend is in place. The relatively new green roofs have come to us to break the monotony of conventional roofs.

Our expert team at TopRemodelers.com  where you can find quality roofers ,have done a little research about the green roof and come up with the following points about them. This can be considered as an introductory lesson to know about the green roofs in order to use it in your building constructions during a renovation. So, read on to know about it here…

So, what is a Green Roof?

In simple terms, a green roof can be defined as the roof of any building that is covered with vegetation along with a growing medium. As such, the roof can be partially or completely covered and will be planted over a waterproof membrane. The green roof, which is very popular in European countries for a long time, has now started attracting a number of homeowners and businesses in the U.S. too. Nevertheless, the benefit of a green roof is the reason why the green roof is becoming popular.

In short, green roofs would give us an impressive way to promote environmentalism when at the same time solving the issues associated with our conventional roofs. By now, you would have got an idea about this. But, you should not forget the main point here. Your green roofs can be able to supplement our traditional vegetation without affecting our urban infrastructure in any way. It’s going to use a neglected in your home and transform it into a useful one.

Now, let’s see the Types of Green Roofs:

The roofing contractors who have subscribed with Top Remodelers have revealed to us that there are three types of green roofs. The categorization of these green roofs is mainly based on the depth of the planting medium we use, as well as the amount of care they require. As such, the green roofs can be of the following types:

Extensive Green Roofs:

In general, the extensive green roofs would require a growing medium of depth two to six inches. Here, the main constituent should be lightweight inorganic substances like:

  •  Perlite
  •  Leca
  •  Sand
  •  Rockwool
  •  Crushed tile/concrete

Remember, we can also include layers such as root barriers, as well as irrigation systems in our green roofs. So, for the extensive type of green roofs, the typical layers would include the following:

  •  A waterproofing layer
  •  An insulation layer
  •  A root barrier membrane
  •  A drainage layer
  •  A filter layer
  •  The growing medium

Here, you must note that the growing medium would be placed above all the other layers. Sometimes, it would be necessary to include drains into the system. These should be boxed in for the purpose of preventing them from clogging up.

There are always ready-grown mats of sedum cultivated within the geotextile pockets packed with substrate available with our roofing contractors working with green roof installation. Such mats are found to be sustained well and are not found to be requiring any watering or weeding processes if the plants you choose are ideal for the climatic conditions prevailing in your region.

As such, we can say that this is the type of roof that would require a minimal maintenance. Thus, a once in a year weeding and the application of slow-release fertilizer for boosting growth would be sufficient for these types of roofs.

Overall, we could see that the extensive types of green roofs are more suitable for those roofs with a less load-bearing capability and for those sites that are not meant to be transformed into a roof garden. When compared to the other types of green roofs, the cost of installation of the extensive green roof will be less.

So, what are the plants that are recommended to be cultivated in the extensive green roofs? When it comes to installing a green roof, we need to take into consideration the stress factors like sun, wind, drought, and others. As such, we would recommend drought-tolerant varieties like the ones that are found in drier mountainous environments, coastal areas, semi-deserts, and dry meadows. All these varieties would have a natural adaptation to the extreme types of climates and hence, they can sustain well in our roofs too. As such, go for a combination of mosses, herbs, grasses, and succulents in order create a good-looking plant community in your roofs.

The most commonly used sedum species are S. acre, S. rupestre, and S. album. You can also try Delosperma if you are living in a sunny region. In drier regions, ferns can be used.

Semi-Extensive Green Roofs:

These are the types of green roofs that require a growing medium of depth four to eight inches. Thus, these roofs can support the growth of perennials. However, you can’t go for cultivating shrubs and trees in these types of roofs. I would say this is the best option to go with when there is a gently sloping shed roof in your building. In these types of roof, you can easily install a semi-extensive type of green roof by building a grid of wooden cells on the top of your roof and packaging those cells with your compost. Just like the extensive types of green roofs, these would also require the following layers to be installed:

  •  Waterproofing
  •  Root barrier
  •  Drainage
  •  Filter

Remember, your semi-extensive green roofs would need twelve to eighteen months to grow. In the meantime, it would need maintenance operations. Unlike the extensive green roofs, these would need hand weeding, watering, as well as feeding. Sometimes, you will also have to perform some replanting activities if you find some plants have failed. As such, the costs are also higher than the extensive green roofs here.

The suitable plants to cultivate in the semi-extensive green roofs would include the grasses, herbaceous perennial species, and your shrubs. As such, you can try growing a combination of two or more of the following plant species:

  •  Rudbeckia
  •  Achillea
  •  Potentilla
  •  Armeria
  •  Dianthus
  •  Helictotrichon sempervirens
  •  Stipa tenuissima
  •  Muscari
  •  Allium flavum
  •  A. pulchellum

Finally, it’s to be noted that the semi-extensive green roofs which are found to be intermediary to your extensive and intensive types of green roofs are the most popular types in America.

Intensive Green Roofs:

As the name suggests, these represent the green roofs that are heavy. Literally, these are the parks or the gardens on your roof. As such, it would require a growing medium of at least one foot deep. And, most part of this would be occupied by your organic matter. These, which are otherwise called as raised beds would require planning, as well as construction by the professional contractors or architects

You should have understood by now that these types of roofs will be heavier than your extensive roofs as these have deeper soils. Therefore, these need to be established on a stronger building structure. Thus, along with the regular inclusions (mentioned above), you can even add benches, ponds, walkways, playgrounds, and much more on your intensive green roof. In simple terms, there are no limitations when it comes to design and uniqueness, although a few things need to be considered.

If you are thinking to establish an intensive green roof, then we would suggest you use lightweight containers. It can be anything made of plastics, metals, or even fiberglass. In these, look in for a sufficient number of holes for drainage purposes. When it comes to growing media, I would again suggest you choose the lightweight ones like compost or rock wool. Why I ask you to go for lightweight media is because the lighter the compost you use, the less time it would take to dry out. Consequently, it would be less heavy for anchoring your plants. In this line, you can even use perlite to further lighten your compost. Alternatively, you can make use of polystyrene in place of your broken pots to reduce the load.

Apart from the above-mentioned elements, you may also need some plant supports like wires and stakes to avoid the damage due to wind rock. You can even consider bracketing the pots to the walls and floors to help avoid blowing over.

Remember, the intensive green roofs would require a higher level of maintenance than the above types. As such, you will have to water the plants all the year round except during the freezing and wet conditions. Here, it’s important for you to note that the rain showers would not penetrate the pots very well. Therefore, you would still need to water them even during the rainy seasons. During the summers, you will have to water them twice in a day. With regards to the watering, I would suggest installing an irrigation system if you cannot keep up with your manual operations.

On the other hand, make sure you have an adequate drainage system to manage the water runoff during storms.

When it comes to plants that can be grown in your intensive green roofs, you must remember that the selection of plants for your community needs to be harmonious with each other. As such, you are advised to choose drought tolerant plant varieties as they would have some kind of resistance to both the sun and the wind. Thus, you can try planting a combination of the following:

  •  Grass
  •  Ground covers
  •  Flowering plants
  •  Shrubs
  •  Trees

Thus, you could bring a biodiversity on your rooftops.

Check out the Strategies for Creating Green Roofs:

When it comes to green roof installation, there are various ways to carry out them. However, remember that irrespective of the strategy used, the initial steps will be the same. Firstly, your roof will be waterproofed and then the structures like root barriers, irrigation, and drainage systems, and your rooftop will be installed. Followed by this, the plants will be set in place or will be planted. Typically, there are three strategies to create your green roof. They are:

  •  Modular: This system would combine several of the green roof’s structures into a pre-manufactured or pre-planted system. These will be placed directly on the roof that has been waterproofed.
  •  Mats: This system would make use of the plantings that are grown off site, which are then installed on the waterproofed roof.
  •  Built-Up: After installing the structures that are mentioned above, the planting medium will be spread on the roof and the plants are then added in your built-up system.

This article was written with the help of  epa.gov


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A Detailed Look at the Green Roofs and their Types

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