Green roofs technological analysis according to a performance-based approach

The research develops with the objective to investigate the technical aspects related to green roofs and evaluate their possible installation on existing buildings. In fact, using these technological solutions for the roof, can be easily implements in the new buildings but collides with multiple difficulties in the existing buildings. In this regard, it is consider interesting to investigate the technological aspects related to these solutions. In order to identify the main constraints that prevent the implementations of green roofs on existing buildings and to define the conditions under which this type of installation can find the effective implementation also on existing buildings, without relevant construction works. The objective of this work is the assessment of the feasibility of the installation of green roofs on existing buildings. In particular, we set ourselves the goal is to be able to identify technological constraints, architectural and structural, that make impossible the installation of green roofs in existing buildings. Based on these assessments, will be to demonstrate that below definite conditions, the installation of green roofs is also possible on the existing buildings. The green roofs are gradually more popular, especially on new buildings, due to the greater sensitivity of the actors in the construction market with respect to issues related to environmental protection and the design of solutions to reduce the energy consumption of buildings. In this context, in recent times, research has provided confirmations about the benefits related to the implementation of green covering on the buildings roofs. In particular, we highlighted the positive impact of the reduction of urban heat island effect, reducing energy consumption for air conditioning in summer and winter and reducing the outflow of rainwater. However, it is not known yet what is the potential of the city to adopt in their already built environment green roofs. In this sense, the work of the proposed research has the target to give a very first contribution to provide the answer to this question. We conduct the analysis by comparing performances of a designed green roof from different technological solutions of the current situation. We evaluated the implementation of intensive and extensive green roofs on existing building with a flat roof. We chose to proceed developing the extensive green roofs, as less onerous in terms of loads and so more suitable for installation on an existing building. We also considered a possible traditional and insulate solution (thermal insulation cover, without the realization of green roof) to replace the existing roof, with which was made comparisons for each category evaluated. For each solution, both at green roof and traditional insulated, we are determined all the values relating to the energy performances of the building and the values of the static load introduced by installations. Last one, evaluated in conditions of saturation of the soil that is the situation more onerous as regards the green covering. Obtained results show that the implementation of a green roof on an existing building, compared to a general improvement of the energy performance, implying a heavier load on the roof. By a purely legal point of view, analysis indicate that the load introduced would not require a revision of the building structure. This is because there is not a change in the roof destination use and the weight of the introduced solution by extensive green roof does not exceed 10% of the load on the building foundation.