When ancient habits marry new technologies, the result is a better life and less pollution; with the concept of green roofs we indicate those roofs of houses, which for centuries have been used in northern Europe, especially in some areas of the Scandinavian countries, where instead of tiles or other material, the coverage of buildings is done with humus or soil, on which they are allowed to develop ground cover, so that they make the roof a real turf. This type of coverage is carried out since ancient times, especially in areas where materials such as slate or clay are difficult to find; the houses so covered are definitely environmentally friendly and life in them is facilitated by the green roof, which helps to well insulate the house from the external climate, improving protection from the cold, from heat, from humidity, from fire.
Green roofs today
With the new technologies the concept of green roof has been modernized and perfected; this type of construction is decidedly more environmentally friendly than the normal covers used. Especially in the city environment, the concept of a green roof can help the urban climate and the very life of citizens; in fact, being able to revive the roofs of the buildings also increases to a great extent the size of the green lungs of the cities, such as parks and gardens; the presence of plants, grass and other vegetation in the city helps to improve the quality of the air we breathe every day, increasing the amount of oxygen present in it. In addition, vegetation helps to filter the air from microparticles, which are particularly harmful to the health of humans and animals.
Moreover, the presence of roofs covered with vegetation can improve the summer climate of very sunny cities, lowering the outside temperature of buildings; the insulating power of the lawn also makes it possible to have a slightly warmer house in winter and cooler in summer: this can be translated, over the course of a year, into less expense for air conditioning systems, and lower emissions of greenhouse gases the atmosphere.
In the city the presence of a good area covered by vegetation and soil also allows the water caused by rain to flow more quickly, especially during periods with very rainy weather.
There are various types of green roofs; the most "old-fashioned" type consists of breaking one side of the building, covering it with earth, which will act as a real roof. The modern green roofs, also called vegetable roofs, are instead made up of a not too deep layer of light and rich humus, consisting of plant material, such as bark, leaves, straw, or other composting material; this insulating and well aerated layer is placed over a good insulating system; a gap is placed between the insulation and the compost consisting of materials that prevent the plants from sinking their roots excessively, insulating them from water, and draining materials, so that the roof does not excessively impregnate water in case rain.
The fundamental differences between an old-style green roof and a more modern vegetal roof concern first of all the weight: the vegetal roof does not weigh much more than a classic roof, and certainly weighs much less than a common garden earth roof; another fundamental difference consists in the use of new materials for drainage and internal insulation of the house, so that the green roof brings advantages and not inconveniences due to the vegetation that develops above them.
Green roofs: What plants on the vegetable roof
The most widespread vegetable roofs are covered with small, low-maintenance ground cover plants, just like the turf in your garden. At the time of installation of this roof it is good to decide to plant the essences that will more easily remain alive given the climatic conditions of the place where the house is located; therefore in a warm and sunny area, with mild winters, they will find space for semi-succulent plants; in very rainy and cool areas we will instead place poacee or other plants generally used for the lawn.
This type of green roof is said to be extensive and the plants that find space there can generally survive for a long time, reproducing spontaneously over the years. This type of vegetation cover is sometimes also used in the construction of green walls, placed perpendicular to the ground. The intensive green roof generally does not require care, except for an initial watering after installation, to favor the first rooting of the plant species planted there.
Another type of green roof is called intensive green: the roof of the buildings is used as a true roof garden; in this case we are dealing with roofs that need a more complex and heavy base structure, so that already starting the building will have to be prepared, since the thickness of usable land will be greater and furthermore it could also be possible to tread on these green areas. The hanging gardens have all the advantageous features of the green roof, in terms of improving the climate of the house and the surrounding area, they need constant and regular care, as they can also accommodate shrubs or small plants, flowers, fruit, and also small vegetable gardens. This type of cover is certainly not suitable for a small family home, but is more suited to large shopping centers, hospitals or large buildings in the city center.