## 2 Materials and Methods
### Roof Suitability: Analysis of Criteria to Assess Rooftop Renovations' Feasibility
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Criteria** & **Green Roof** & **High-Reflectance Roof** & **Solar Technology** \\ \hline Building height & \textgreater{}3.5 m (heated building) & \textgreater{}3.5 m (low building) & \textgreater{}3.5 m (heated building) \\ Roof area & \textgreater{}100 m\({}^{2}\) & \textgreater{}20 m\({}^{2}\) & \textgreater{}50 m\({}^{2}\) \\ Roof material/color tones & No high-reflectance, vegetated and red-tiled roofs & No high-reflectance, vegetated and red-tiled roofs & No rid-tiles roofs \\  & \textless{}11\({}^{\circ}\) intensive (flat) & \textless{}8.5\({}^{\circ}\) low sloped & \\ Roof slope & \textgreater{}11\({}^{\circ}\) and \textless{}20\({}^{\circ}\) extensive (pitched) & \textgreater{}8.5\({}^{\circ}\) steep sloped & \\ Roof orientation & No limit & No limit & No North exposition \\ Solar radiation & Related to shadow criterion & No limit & \textgreater{}1200 kWh/m\({}^{2}\)/year \\ Shadow effects & Sunny roofs with more than 3 h & & Related to solar \\  & of sunlight & No limit & radiation criterion \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Criteria to assess rooftop renovation feasibility. \(P\) is the installed electric power (kW),  
\(K\) is a coefficient equal to 50 (m\({}^{2}\)/kW) after 1 January 2017, and  
\(A\) is the footprint area of the building (m\({}^{2}\)). For roofing structures of buildings, verification of the effectiveness, in terms of cost-benefit ratio, was assessed referring to (according to Italian Decree 28/2011):  
* Materials with high reflectance of roofs, assuming for the latter a solar reflectance value of not less than 0.65 in the case of flat roofs and 0.30 in the case of pitched roof. * Passive cooling technologies (e.g., night ventilation and green roofs). Furthermore, the Solar Reflectance Index (_SRI_) is used in the main international certification protocols for comparing the coolness of roof surfaces. In Italy some voluntary environmental protocols have been introduced, such as the ITACA (Institute for Innovation and Transparency of Procurement and Environmental Compatibility) protocol, Casaclima Nature certification, and the Green Building Council (GBC) Italia, in which _SRI_ levels for roofs have been specified. In addition, from the enactment of the Italian Decree 11/01/2017, the Ministry for the Environment, Land and Sea has established the \"Adoption of minimal environmental criteria (CAM) for the awarding of design services and new construction, renovation and maintenance work on buildings for management of construction sites of the public administration and minimal environmental criteria for the supply of incontinence aids\", thus aligning itself with environmental protection strategies adopted at an international level. The section \"Reduction of impact on the microclimate and atmospheric pollution\" establishes the requirement of materials with a high _SRI_ (Table 3). The Municipality of Turin regulates the roof elements through a number of rules, as shown in the image below. Current regulations determine rules to design roofs in relation to geometry, structural characteristics, heights, and architectural appearance. Such regulations also define restrictions to design intervention and uses according to functions and zoning of the masterplan, limiting, in particular, changes in the historical center of the city. Moreover, while the Building Annex Energy Code in place calls for environmental awareness by setting compulsory requirements for thermal insulation and derogations to enable the installation of solar and photovoltaic panels, the conversion into green surfaces is only mentioned within the voluntary requirements, leaving the economic burden to the private owners and the limitation of opportunities to out-of-date regulations. To overcome such limitations, and after the identification of criteria to evaluate rooftops' renovation feasibility, the rooftops' potential was investigated for a district in Turin (IT) and the impact of smart-green technologies was evaluated and quantified using several indicators.