Part of the architecture is responsible for achieving more sustainable designs to improve energy performance and reduce environmental impact. One of the techniques used for this is vegetation cover. Ground cover has many advantages that we will analyze one by one.
In this article we will tell you what a green roof is, what its features are and why it is important.
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What is a green roof?
A green roof on a building is a green roof which, together with a roof containing solar thermal or photovoltaic panels or protected by a high reflectivity material, increases the energy efficiency of a building because together they save Energy. Energy behavior of a building in relation to its environment. Also called green roofs or garden roofs, there are different types.
Green roofs are a type of roof already used in the Nordic countries as insulation. Thanks to its thermal inertia, it controls humidity and regulates the interior temperature. In countries like Iceland, Norway or Canada they are used to insulate, because the vegetation on the roof accumulates heat in winter, while in hot countries like Tanzania they keep the interiors cool despite the external solar radiation.
In the city of Copenhagen, The new roof owners have made it mandatory to plant some type of greenery on their roofs. Other countries have regulations that regulate and/or reward the installation of green roofs. It turns out that green roofs help reduce the temperature in cities. It is not about filling all buildings in urban areas with green roofs, but the wise use of technology can reduce the heat island effect caused by high density buildings, traffic or the use of air conditioning equipment. The heat island effect occurs in cities, where temperatures can rise up to 10 degrees above surrounding areas.
Green roof in LEED
LEED tools include, as a sustainable strategy, the installation of a green cover for all the environmental and economic benefits in the category of sustainable grounds:
- Reduces stormwater runoff and reduces the risk of flooding since they retain a high percentage of precipitation up to 90%, then part evaporates and the rest is directed in a delayed way, and improves its quality by filtering pollutants and heavy metals from rainwater.
- Filters pollutants and carbon dioxide from the airreducing pollution through natural processes.
- It reduces energy consumption because it provides thermal insulation. Due to the thermal inertia that the plant cover as a whole can provide, it can act as a regulator of humidity and internal temperature.
- Increases roof life because the waterproof barrier is protected from solar radiation, heat and cold and storms.
- Reduces heat island effects in urban environments and develop green spaces to plant or recreate depending on the type of vegetation cover.
- Promotes biodiversity since it allows the growth of the species. Developing an urban garden on the roof of an urban environment could be an interesting option, even offering the possibility of growing our own products “at home”.
green roof elements
The plant cover is made up of the following parts:
- Waterproof jacket. It is placed on roof supports – slabs – for this type of roof they must be resistant to roots. Common practice is to use sealing materials such as EPDM, which consists of recycled rubber, or PVC, which is also recyclable. If a flashing board being used is not ready to prevent root breakage, a double-ply board and some type of root protection primer should be applied.
- Thermal insulation. Some green roofs include a layer of insulation.
- drainage layer. Among its functions is to drain water from the roof, avoiding water stagnation and thus preventing the formation of fungi in the roots of plants. It can consist of a layer of gravel or a layer of HDPE. Polyethylene is a plastic that can be recycled.
- Retention layer. This layer has a concave surface so that it can store water from the roof. The drainage layer and the retention layer can be unified into one layer.
- Filter layer. It consists of geotextiles whose function is to prevent the remaining layer of substrate from being washed away. By avoiding leaching, the substrate retains its properties, promoting plant growth. It is laid on a draining layer, normally in 125 g/m² polypropylene.
- Absorbent layer. The main function of this layer is to retain moisture and release it gradually, especially in dry climates, with little maintenance of the vegetation cover and rapid evaporation of water. It can be part of the substrate itself or be placed under it.
- Substrate. This is the land where plants take root. It must have the right nutrients and acidity for the type of vegetation it is grown in. The ideal thickness is usually between 4 and 15 cm. The height of the vegetation should not exceed 50 cm.
The substrate is used as a base for the growth of the selected vegetation. In addition, a protective layer can be placed that prevents the growth of plants other than those that need it and synergistically keeps the substrate moist. This is very convenient in dry climates as it reduces the need for watering. For this, stuffing materials, pine bark, volcanic gravel, etc. can be used. to reduce evapotranspiration, especially in dry climates.
Copenhagen does not seem to be an isolated case of this trend or obligation to fill cities with green roofs. The digital newspaper lasprovincias.es published in March 2010 that a revision of Valencia’s master plan, which runs until 2025, may require green roofs on new buildings. A strategy based on environmental criteria to improve the energy efficiency of urban landscapes and buildings.
I hope that with this information you can learn more about what a vegetation cover is and what its characteristics are.