Green roofs clean the CO2 air, act as thermal and acoustic insulators, regulate ambient humidity and, as if that were not enough, beautify buildings and restore roofs as living spaces.

Perhaps inspired by the picturesque and traditional houses of the Faroe Islands, green roofs are growing interest among lovers of sustainable housing. Also known as green roofs or green roofs. FORWhile they may seem like newcomers to urbanism and sustainable architecture, they have many years of history.

What are green roofs?

The installation of this type of green roof based on moss, grass or flowers insulates the house against noise and low temperatures. Thus promoting energy savings, reducing the risk of flooding, extending the useful life of roofs, and also filtering CO2 from the surrounding air. There is also the possibility of growing vegetables or herbs and even making a roof garden with shrubs or small trees.

These roofs use a drainage system and waterproofing that prevents vegetation from damaging the building’s structure. They only need a thin layer of soil between 5 and 10 centimeters in the case of extensive green roofs, that is, the most popular and used, because they are the lightest and require little maintenance.

Benefits of green roofs

Converting roofs and terraces into small lawns or gardens offers much more than its obvious, though not less, ornamental quality. Your contribution to Energy saving Still to improving air quality Among other advantages, they have made it a technique to be taken into account in the construction of sustainable buildings.

The green roofs represent savings in both heating and air conditioning, since the thermal inertia of the earth layer is capable of maintaining a difference of two to three degrees in relation to the external temperature.

In fact, this feature was already used in the past in the Nordic countries, where they covered their wooden huts with a layer of soil. In addition, this soil layer also acts as humidity regulatorbecause if the external environment is dry it releases it, and if it is humid it absorbs it.

The benefits of green roofs go beyond the limits of the house they cover and extend to the rest of the community. Roofs can be a solution to urban land scarcity to create new green areas that help absorb CO2 from the atmosphere and thus provide cleaner and cleaner air for citizens.

In addition, green roofs help to reduce the effect “heat island”, Localized increase in temperature in cities that can reach two degrees. This phenomenon occurs because of air conditioners and overheating of conventional roofs, among other factors.

Green roofs in the city

One of the few uses that were given to community terraces was to “go up” to hang clothes, which today is increasingly becoming an extravagance.

Many of the terraces in our cities are forgotten until it is time to install an air conditioner or repair the television antenna.

A green roof would embellish these arid spaces and offer a pleasant place to get together or just go for a break. In fact, the green roofs synthesize the instinct or tradition of decorating balconies and terraces with plants, with the ancestral use of the land as protection against the weather, integrating everything in the building.

In this type of coverage, the ability to retain a certain amount of water is important both for the subsistence of vegetation and for the thermal stability of the entire coverage. For this, one of the layers that make up the cover is formed by hollow cavities, as if it were a box of eggs, in which a small amount of water is deposited.

At the same time, this layer allows excess water to drain and creates a chamber that allows air to circulate and prevents putrefaction. When it rains, excess water can be collected in a tank and used for irrigation or other uses. This ability to retain water is also an advantage in the event of heavy rain, as it would help to relieve pressure on drains and sewers and could be the first stop for floods.

For all this one good waterproofing to prevent leaks, the asphalt primer base is essential. To guarantee the success of the coverage, and that it has a long useful life, its execution must be entrusted to a professional, usually a technical architect, who knows the most appropriate solutions for each case and the materials to be used.

The first thing that the professional will calculate when installing a green roof is the overhead that the building structure can support and, if necessary, propose the right type of reinforcement. This will depend on the type of roof you want to install, which are basically divided into two types: extensive and intensive.

While the extensive ones are intended for herbs or small plants and it is not allowed to step on them, the intensive ones support a thicker layer of soil where you can plant bigger vegetation, even small trees, and walk on it. The choice will depend on the use we are going to give to the coverage and the maintenance that we are willing to assume.. In an industrial warehouse or office building where aesthetics don’t matter so much, they will prefer a cover of wild herbs that, with little maintenance, already offers all the energetic and environmental advantages.

The implantation of green roofs in our country is still difficult, contrary to what happens in other European countries. It is estimated that, in Germany, 15% of new buildings have a green roof, and in Berlin industrial buildings are forced to adopt it. Great Britain, Sweden, United States or Japan, are some of the countries where the installation of these covers is also promoted. Although there is already a line of developers that opt ​​for green buildings, for the rest the extra cost and that “culturally a roof full of grass has not yet been accepted”, still represents a brake for green roofs to stop being a curiosity in our country .

Green roofs for intense roofs

On the other hand, those that incorporate large or very dense plants are called intensive green roofs. Its maintenance and conservation are more complex and include irrigation, fertilizers, better insulators and a soil thickness of at least 20 centimeters. These roofs often simulate small gardens and, in some cases, you can walk through them.

In the case of opting for an intensive green roof, maintenance will be equivalent to a conventional garden. The extra cost of a green roof compared to a conventional one is about twenty percent higher.

Are green roofs suitable in all situations?

Despite the advantages that this type of coverage can bring to houses and buildings, they are not always recommended. They have a clear limitation, the need for water. Therefore, in areas of little rain or very dry These roofs represent an unnecessary expense or even waste.