*Article* **Smart Solutions for Sustainable Cities—The Re-Coding Experience for Harnessing the Potential of Urban Rooftops**

#### **Valeria Todeschi 1, Guglielmina Mutani 2,\*, Lucia Baima 3, Marianna Nigra 4 and Matteo Robiglio 3**


Received: 16 September 2020; Accepted: 9 October 2020; Published: 13 October 2020

**Featured Application: This work presents the analysis of the element of the 'roof' as a methodological approach to assess the renovation opportunities of existing rooftops, as a stimulus to mitigate the urban phenomena of heat island mitigation by focusing on the role of codes, policies, and regulations in cities.**

**Abstract:** Urban rooftops are a potential source of water, energy, and food that contribute to make cities more resilient and sustainable. The use of smart technologies such as solar panels or cool roofs helps to reach energy and climate targets. This work presents a flexible methodology based on the use of geographical information systems that allow evaluating the potential use of roofs in a densely built-up context, estimating the roof areas that can be renovated or used to produce renewable energy. The methodology was applied to the case study of the city of Turin in Italy, a 3D roof model was designed, some scenarios were investigated, and priorities of interventions were established, taking into account the conditions of the urban landscape. The applicability of smart solutions was conducted as a support to the review of the Building Annex Energy Code of Turin, within the project 'Re-Coding', which aimed to update the current building code of the city. In addition, environmental, economic, and social impacts were assessed to identify the more e ffective energy e fficiency measures. In the Turin context, using an insulated green roof, there was energy saving in consumption for heating up to 88 kWh/m<sup>2</sup>/year and for cooling of 10 kWh/m<sup>2</sup>/year, with a reduction in greenhouse gas emissions of 193 tCO2eq/MWh/year and 14 tCO2eq/MWh/year, respectively. This approach could be a significant support in the identification and promotion of energy e fficiency solutions to exploit also renewable energy resources with low greenhouse gas emissions.

**Keywords:** energy e fficiency; smart rooftop technologies; green roof; solar energy; urban heat island; building codes; energy policies; 3D roof city model; urban landscapes
