A green roof is a constructive solution that improves the thermal insulation of the building, enhances the urban microclimate, improves air quality and creates a natural habitat for fauna and flora. It's made with a waterproof membrane over the slab, thermal insulation, draining layer, earth substract and a final layer of plants. The plants should be selected considering sun exposure, local climate and rain levels. To reduce the maintenance the plants should have good resistance levels to high temperatures and low humidity levels.
Green roofs are an extra thermal insulation layer to the building, helping to reduce the energy consumption in more than 15%, as well as an acoustic insulation as they can reduce the sound reflection till 3dB and increase sound insulation till 8dB.
Another benefit is the reduction of rainwater waste in more than 50%, since part of the water is retained by the vegetal layer, reducing the capacity need of the downspouts and drains.
There are several environmental benefits such as the reduction of heat island effect, retention of poluent air particles and creation of natural habitats for plants, birds and insects.
In terms of costs, the initial construction of a green roof can be twice as expensive as a traditional roof. However, this cost is offset in long-term through the reduction of energy consumption, reduction of maintenance cost in the waterprooof membrane and reduction of the cost of the drainage system.