**1. Introduction**

This paper presents some of the results of the Re-Coding research project, undertaken by the Research Centre Future Urban Legacy Lab (FULL) in collaboration with the Responsible Risk Resilience Centre (R3C) of Politecnico di Torino. This project was carried out in support of the current review of the General Development Plan of the city of Torino, Italy. Such research explored the relationship between codes and city morphology with the aim of expanding the scope of the existing building regulatory system to a wider encompassing environmental system of codes that could support the sustainable development of the city. A number of studies across disciplines are currently looking into the role of planning and coding in the definition of policies and regulations for environmental improvement of our built environment [1–4]. Conversely to the traditional planning approach of zoning, such studies discusses the importance of building codes to trigger e ffective changes on the urban scale by intervening on punctual aspects such as the environmental quality of building parts. Not only within the academic discourse, but also in practice current tendencies of policies and regulation systems tend to focus on the need of environmental awareness with such approach. This is the case, for example, of the cities of New York, with the OneNYC 2050 and Climate Mobilization Act, and of Marseille, with its regulatory planning and coding system, in which punctual actions are determined with simple rules to improve environmental performances. As [1] explained, the complexity of a regulation system might hinder the immediate understanding of the extent and impacts that such regulations have on the built environment, particularly when the overlapping of well-intentioned regulations generated in di fferent time frames result in out-of-date or ine ffective rules. For this reason, the Re-Coding project is aimed at redefining the rules starting by the analysis of 'building elements' as the interface between users (i.e., architects, private owners) and institutions. To this end, about 42 elements (i.e., windows, roof, external walls, and others) across scales have been identified and utilized as navigators to allow the mapping of current regulation systems.

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. The results of this analysis and exploration were used to propose and define modifications in the current regulations. Such modifications were aimed at actively promoting sustainable changes in the urban environment, in particular, by providing data to support the modification of the Building Annex Energy Code, currently in use in the city of Turin.

#### *The Premises of the Research*

The roof element was analyzed as a device that relates both environmental issues and the revision of the related regulations that define the relationship between urban morphology and the impacts on its ordinary transformation. Moreover, the roof could be considered as the fifth facade of buildings and its surface can be rethought as a platform for multiple uses, action, and potential transformation effects on the city [5,6].

Within this conceptual framework, the focus of the work was to tease out the opportunities o ffered in rethinking the roof element not only as a separation device between two environments, internal and external, but as a surface capable of catalyzing multiple functions related to urban living.

The analysis of international case studies (e.g., New York, Paris, Marseille, Melbourne, and Lisbon) started in the first phase of the research through the application of a matrix, which allowed the comparison of the design strategies adopted in relation to the current legislation. The matrix utilized is based on the innovation theory applied to architectural and urban design, defined first by Slaughter [7] and later elaborated by Nigra and Dimitrijevic [8]. Such matrix categorized each case study according to type of change, according to the definitions of incremental change, modular change, architectural change, system change, and radical change. These categories define di fferent natures of change. The incremental change is defined as a small change that does not a ffect the overall nature of an intervention. The modular change is a change that influences a single independent part of a project. An architectural change is a change that alters the relation between major architectural and compositional elements. The system change is a change that alters the overall system functioning by increasing its performance. The radical change is a change that transforms totally the nature of an existing condition. The following table shows the application of these concepts to a number of case studies analyzed, in relation to the type of intervention done on the roof elements on certain projects.

The matrix above (Table 1) highlights the different opportunities to conceive roofs as a resource in relation to both the building system and the city system. The case studies analyzed allowed us to amplify the image of the functions that the roof element can accommodate: Temporary solutions that rethink the roof as a support for site-specific works or a platform hosting light devices for autonomous functions or that extend and intensify the functional program of the building, creating different relationships with the city up to the roof, rethought as a system-generative platform, which increases the building's performance.

Rereading from this perspective, the idea of roofs and the surfaces made available emerges as an additional layer on the city, an infrastructure of latent potential to be activated through a constant dialogue between the project and the regulations [2,3,9].

Following are the main objectives of this work were:



## **2. Materials and Methods**

The methodology described in this section was applied to a case study of the city of Turin. The city is located in the northwestern part of Italy and has a continental climate and almost 900,000 inhabitants. The aim was to assess the applicability of rooftop renovation strategies in a built-up context at district level, investigating environmental, social, and economic impacts of smart roof solutions. Figure 1 describes in detail materials, methods, and tools used in this.


(4) Roof solutions: The most effective rooftop strategies were identified to improve the livability conditions of the city of Turin, and the impact of smart technologies was investigated.

**Figure 1.** Flowchart of materials, methods, and tools.

#### *2.1. GIS Database: Input Data Collection and Processing*

Building upon an ongoing research, a territorial database (DBT) was organized and implemented with the use of a GIS software processing remote sensing images, orthophotos, building characteristics, land cover data, local climate measurements, and energy consumption data. The main data content refers to:


employment rate, socio-economic data (income at 2009), central or autonomous heating systems, and type of fuels.


After the processing of these data, the three main outputs used in this work were a 2D vegetation model, a 3D roof city model, and urban-scale energy models with annual, monthly, and hourly time resolutions.

#### *2.2. GIS Tools: Analysis of Building and Roof Typologies*

The analysis of roof typologies and the urban environment was carried out using several tools, explained below.


By overlapping the results of the statistical analysis, the disturbance percentage for each roof was assessed, identifying three classes of disturbance: 15, 25, and 35% [23].

Some outputs of the application of the described methodology are indicated in the following figures. Figure 2a shows the building typologies of a district of Turin with a dimension of 1 km × 1 km. Such classification was made using information on type of users, building height, and the *S*/*V* ratio values. It is possible to observe that almost 80% of buildings are residential, mainly linear blocks and towers [13]. Figure 2b describes the roof typologies, distinguishing six categories: flat, gable with E-W orientation, gable with N-S orientation, half-hipped, hipped or pyramid, and shed. In this pre-analysis, it was noticed that there is a potential of flat roofs that could be converted into green roofs (Figure 3a), the presence of low buildings with dark surfaces could be converted to light surfaces (high-reflectance roof), reducing the environmental temperature (Figure 2a), and a large quota of residential buildings has an optimal E-W orientation for solar energy production (Figure 3b).

**Figure 2.** District of Turin with a dimension of 1 km2: (**a**) Identification of building typology using type of users, building height, and surface-to-volume (*S*/*V*) value; (**b**) identification of roof typologies according to [23].

**Figure 3.** District of Turin with a dimension of 1 km2: (**a**) Roof typology analysis and roof area; (**b**) building orientation analysis and roof area.

#### *2.3. Roof Suitability: Analysis of Criteria to Assess Rooftop Renovations' Feasibility*

This section presents the criteria used to evaluate the feasibility of rooftop renovation and to identify the correct rooftop strategy as a function of urban environment. These criteria refer to building architecture, morphological context (Table 2), building codes, and regulations.

The information of buildings' architecture and morphological context were investigated using the DBT presented in Section 2.1. According to Italian Standard (UNI) 11235:2015 and to the literature review [13,24–27], the following criteria were identified to select the potential roofs.



**Table 2.** Criteria to assess rooftop renovation feasibility.

The feasibility of energy efficiency interventions was assessed considering energy and environmental regulations at national and municipal levels. According to the Italian Decree 28/2011, some requirements were considered for the installation of solar energy technologies:


$$P = (1/K) \cdot A \tag{1}$$

where:

*P* is the installed electric power (kW),


#### *Appl. Sci.* **2020**, *10*, 7112

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):


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 managemen<sup>t</sup> 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).


**Table 3.** Italian voluntary protocols and requirements.

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.

#### *2.4. Impacts of Smart Roof Solutions and Technologies*

From the literature review [8,28–37], it emerged that the main roof technologies able to obtain a positive impact on the urban heat island (UHI) mitigation, on the energy consumptions and savings, on the outdoor and indoor thermal comfort conditions, and on social and economic aspects are green and high-reflectance roofs and walls and the energy production from PV panels and ST collectors.
