Green roof: advantages, types (extensive and intensive), costs, thickness and permits. Complete stratigraphy of an intensive and extensive green roof.
Thegreen roofit's aplant coverwhich has its roots in the traditions of many European countries. If for us Italians thegreen roofis an innovation linked togreen building, in the architectural history of the Scandinavian countries thegreen roofit is an authentic tradition.
Green roof, advantages
The mix of earth and vegetables planted onroofsallows you to create well-insulated roofs, protected from air and water, resistant to wind and fire. The making of agreen roof it should be entrusted to a qualified technician, especially if it is an intensive green roof. Maintenance depends on the type of vegetation chosen. Undoubtedly, an intensive green roof will require constant maintenance and care, while for an extensive green roof made with slow-growing herbaceous plants, one intervention per year will suffice.
There are many advantagesrelated to the preparation of agreen roof. The vegetalized roofsplay an important insulating role and i advantages economic are many: a simple decrease of 1 ° C in the surface temperature decreases the electrical needs of the home by 5 percent, this reduction is linked to the lower demand for electricity for heating and cooling of the rooms.
Other economic benefits include duration: igreen roofslast twice as long as ordinary roofs, plus onegreen roofit can be used for agricultural purposes. Always remaining among the advantagesin the economic sphere there is the real estate value: the cost of a house increases with a green cover!
Betweenadvantagesenvironmental we see that thegreen roofit absorbs heat, reduces the use of electrical appliances allowing a cut in harmful emissions, in addition, the vegetation filters the air eliminating polluting particles. In practice, the air around the house will be cleaner.
For the collective well-being, igreen roofsthey decrease the thermal island effect typical of urban centers, relieve the sewer system by absorbing water and significantly reduce the temperature in summer. How come they cushion the "urban island" effect and lower summer temperatures? This occurs because the turf absorbs the energy of the sun while the classic roofs reflect the solar energy in the form of heat. In other words, the perimeter air of the house will be cooler.
Pitched green roof and extensive green roof
The green roof of typeextensiveit is the easiest to access: it requires smaller thicknesses, lower load capacities and almost never requires preliminary structural interventions.
Theextensive green roofit is particularly suitable for large buildings and forsloping roofs. It is characterized by athickness and a lighter weight.
Green roof: thick and heavy
Aextensive green roofhas onethicknessof substrate which varies from 10 to 15 cm approximately.
Theweightof theextensive green roofit can vary from 30 to 100 km per square meter at maximum water capacity. Aextensive roofit needs less maintenance and is watered only in case of prolonged drought.
Usually, to set up aextensive green roofmosses, grasses or succulents are planted, so we are talking about very resistant and slow-growing vegetation: the height of the plants of aextensive green roofit never exceeds 25 cm and the association of several plant varieties gives themroofsan aspectmulticoloredwhich varies according to the seasons. The only drawback of theextensive green rooflies in the fact that it cannot be trampled on or even cultivated.
Walkable green roof: the intensive green roof
It is wrong to speak of a "walkable green roof", rather it should be defined as "practicable": the intensive green roof gives the possibility to set up a real roof garden, complete with plants, a vegetable garden and flower beds!
Unlike theextensive green roof, thatintensive, has a higher thickness, we are talking about 20 - 40 cm for an overload weight between 120 and 350 kg per square meter at maximum capacity in water. Theintensive green roofit can be cultivated but for its construction it will be necessary to contact experts to find out if the building structures can support the load.
How much does a green roof cost
In the article "Green roof: cost and how to do it" we provided information on the price of the turnkey green roof, including installation and purchase of tree species. The cost varies as much betweenintensive and extensive green roof, it can also significantly increase if the structure of the house is not already suitable to support a certain load, and therefore requires preliminary work to set up a roof garden!
Permits to build a green roof
The bureaucratic process to follow is simple but varies from municipality to municipality: it is necessary to inform yourself that there are no architectural, historical or landscape restrictions in your area. The Municipality must submit the appropriate building practice signed by the qualified technician who will implement thegreen roof.
Green roof: stratigraphy
Thegreen roofit is made from several layers of material and for this it is spoken ofstratigraphy. Therestratigraphythat we commonly find online is only general, in fact each green roof can have its own needs. Again we provide you with onestratigraphygeneric of the typical example ofgreen roofwith natural soil. The stratigraphy sees five different bands that reproduce the structure of the natural soil:
- Vegetable plant
This is the terminal layer, more visible, it includes plants of different species according to the type of green roof (intensive or extensive).
- Growth substrate
It is called the crop layer and forms the culture medium. It is made up of light compost. It can have a different thickness depending on the type of plants to grow. For example, for ornamental plants a thickness of 15 cm is required, for saplings and hedges, it is 100 cm thick. For a simple lawn 7 cm is enough.
- Filtration membrane
It serves to retain the soil and to filter the water into the underlying drainage layer.
- Drainage and water storage
It is a layer consisting of gravel or polyethylene, designed to dispose of the rain by retaining a small part to be gradually returned, in the form of moisture, to the soil above.
- Waterproof membrane
It is the insulating layer of crucial importance. It is made up of synthetic materials and replaces the classic waterproofing already present on roofs.