Analysis of Renovation Works in Cappuccinelli Social Housing District in Trapani

The refurbishment of public residential districts represents a current and complex problem. The Cappuccinelli Social Housing (SH) district in Trapani, designed in the late 1950s by Michele Valori and built during the 1960s, is emblematic of the architectural quality and technological innovation of the time it was designed, but at the same time represents the physical and social decay that occurred just after its construction. The neighborhood was examined through a combination of inspections and documentary research. The inspections were conducted for the entire district in order to identify the recurrent external degradation of building components and the related causes, both physical and anthropogenic. This paper investigates the physical–mechanical degradation and problems connected to previous renovation work in this district. Furthermore, technological design solutions are discussed for deep renovation and energy efficiency improvement of one of the terraced buildings of the Cappuccinelli SH district.


Introduction
The importance of deep renovation to existing building stock, recently stressed by the European Commission [1], is well-established in Italian regulations and strategies on buildings and their performances [2].
Public housing districts are relevant in this context, as demonstrated by several researchers investigating their renovations in European countries [3]. Several efforts were dedicated to joining architectural retrofit aspects with energy-saving requirements. In [4], the energy renovation of a city district in a particularly challenging historical city center is presented. The authors carried out an energy assessment of different interventions applied to the SH district in Venice. The introduction of vegetation for climate mitigation in urban contexts and for the energy improvement of individual buildings is widely studied. In [5], the benefits arising from the application of nature-based solutions in urban districts are examined. A set of simulations showed an improvement in the overall comfort conditions of inhabitants in terms of "urban heat island" reduction and living wellness. In [6], the author argues that additions on the façade have considerable advantages for the recovery and improvement of the energy performance of buildings, and proposes this solution be applied to public housing buildings, in accordance with Gaspari J. in [7,8]. Interventions on the building envelope allow for not only improvements in the energy performance of buildings, but also improvements to their appearance and architectural quality, giving new life to public housing. BIM is a new method used to optimize the planning, construction, and management of building artifacts using the software. Through the use of BIM software (Last Planner, Plan Radar, Vienna, Austria), it is also possible to validate the economic benefits of the recovery of public housing. In this study [9], 4D BIM technology was applied to a case study in Northern Ireland to validate the effectiveness of the software in cases of social housing retrofit, a condition not particularly studied by the scientific community. The authors argue that their model could be expanded to all UK buildings. The authors of this article [10] analyzed Portuguese residential construction in order to demonstrate that the recovery of existing buildings, using a minimum economic investment and ensuring energy improvements, is essential for a sustainable economy. Roof renovation is the most cost-effective measure for improving heating and cooling thermal performance. A study conducted by researchers at the University of Seville [11] in Spain demonstrates how the application of a ventilated roof in a Mediterranean climate allows for a 65% reduction in cooling requirements without a consequent heating penalty.
Social Housing districts are a significant portion of the existing building stock and are frequently based on architectural solutions which are worth being preserved although not optimum for achieving the current technical requirements set for existing buildings. Furthermore, these districts are often affected by large amounts of physical degradation due to lack of maintenance and social marginalization. Finally, they often host vulnerable inhabitants, who should be the primary beneficiaries of public strategies for building renovation. In this regard, solutions aiming at improving both the buildings' energy efficiency and urban environmental quality are considerably effective and also provide relevant social outcomes [12].
The present paper focuses on the public housing district called "Cappuccinelli" in the Sicilian town of Trapani. Cappuccinelli is strategic in the sustainable development of Trapani since it is situated both along the waterfront and on one of the main roads of the town. At the same time, this area is vulnerable to hydrological risks since it is located on a swamp that was reclaimed at the end of the 1930s.
The district is the result of an interesting architectural project [13]. However, it also suffers from relevant physical decay (evident in the number of unauthorized additions and the lack of regular maintenance), which has fostered significant social problems. Because of these weaknesses, for a long time, the municipality ignored the potential of Cappuccinelli for its inhabitants and the town as a whole. Recently, thanks to an announcement issued as part of the National Innovation Program for the Quality of Living [14], the municipality has included the district among the sites selected for regenerating the urban, building, and socio-economic heritage of Trapani in order to improve social cohesion and guarantee the quality of life of citizens with a sustainable perspective. This paper investigates Cappuccinelli as a reference case to develop planning and design procedures for the refurbishment of Italian public housing districts. In this sense, the circumstance that around 62% of dwellings in Cappuccinelli are owned by private parties-generally, the inhabitants themselves-and not by a public body is relevant given that this is a frequent barrier to urban-scale improvement strategies and renovations of Italian social housing districts.

Methodology
The research method adopted by the authors started with the analysis of Cappuccinelli Social Housing district through a detailed examination of a combination of documentary research, onsite inspections, and monitoring activities related to the thermal transmissions of external walls as discussed in previous work [15].
Documentary research was carried out at the archive of the public body "IACP Trapani", which is responsible for public dwellings in the Cappuccinelli district [13]. Two main objects were explored. First, project development was detailed from the awarded architectural concept to the construction of the district, which was characterized by several changes to the original design [13]. Secondly, technical documents of the renovation works carried out by IACP were examined and categorized according to the building and period of execution.
General onsite inspections were conducted for the entire district in order to individuate recurring outdoor degradations of the building components and their related causes, both physical and anthropogenic.
The alterations, classified according to the technical standard UNI 11182:2006 [16,17], were documented by means of photographs and geometric surveys. As far as the anthropogenic degradations are concerned, the types and locations of inappropriate external and structural changes, façade changes in façades (especially for openings), and unauthorized additions were reported systematically. Information collected about damages and alterations in the different blocks was related to the positions of the blocks in the district (especially for their exposure to wind and sea salt aerosol) and the rates of private and public owners per building.
As described in the following section, the study was widened to two blocks, where a detailed analysis of external degradation of the building envelope was carried out. For this purpose, a photogrammetric survey was carried out.
The additional data achieved through the focus on two blocks were used to define an order of priority for urgent renovation works [18] and discuss the technical proposals appropriate to match the deep renovation of the Cappuccinelli district with its architectural features.

Cappuccinelli Social Housing District
The "Cappuccinelli" district ( Figure 1) was built as part of the national plan of social housing called "INA-Casa", which was implemented by Italian Law 43/1949. Architect Michele Valori and his group designed the district for a design contest in 1956. A large square is surrounded by two-storey blocks, each including large inner courtyards, and a multi-storey building. The idea, on which the project by Valori is based, creates a strict relation between private and public spaces that are linked by buildings, predominantly terraced houses with different typologies of apartments.
The "courtyard blocks" consist of duplex apartments with four to five rooms. These dwellings are organized in pairs and each one has a small courtyard that is accessible from a portico. This private courtyard is separated from the large common courtyard of the block, which is accessible from a secondary access point at the back of the apartment. The ground floor of each pair of apartments corresponds to a square. One side of this square is 12.60 m long and corresponds to the module that the district is based on. In the original project, the inner courtyard of each block was dedicated to extensive vegetation with private gardens, equipped areas, and a limited number of tall trees.
The phenomena of social decay impacted Cappuccinelli from the beginning. Many houses were illegally occupied even during the construction work, thus impeding the completion of the district according to the original project plan. Furthermore, unauthorized additions have proliferated: The small courtyards of paired duplexes were frequently closed and many private gardens in the large courtyard were changed to indoor spaces ( Figure 2). Physical and mechanical decay join the anthropogenic alterations of the courtyard blocks. Indeed, the buildings have a reinforced concrete-framed structure with infill walls comprising two layers of calcarenite blocks with an air cavity. Close to the sea and exposed to strong mistral winds, the structures suffer severe degradation from metal corrosion that has been accelerated by defective rainwater disposal from roofs. This implies extensive damage to the plasters and localized losses of the outer layer of the infill walls.
The analysis of the district has focused on the two blocks named "E" and "L" (Figure 3). Both have the same modular units as the courtyard blocks, namely a pair of duplex dwellings, but block "E" has an open courtyard while block "L" is a linear block of terrace houses.

Deep Renovation Works
In the examined blocks "E" and "L", renovation works have been carried out frequently in the last three decades, as reported in the archival documents [19]. The realized works include the demolition and reconstruction of the roofs, the restoration of reinforced-concrete structural elements, and the removal and replacement of plasters. Table 1 summarizes the works carried out from 1992 to 2005 in the two analyzed blocks. Refurbishment of reinforced-concrete pillars and beams, and floors. Demolition and reconstruction of roof slabs with precast elements in brick concrete, 20 cm thick (16 + 4). Partial replacement of infill walls with precast concrete blocks subject to water repellent treatment. Dismantling of water tanks placed on the roof. Refurbishment of water and electrical systems in a dwelling.

E, L 24
Refurbishment of reinforced-concrete structural elements. Demolition and reconstruction of roof slabs. Removal of water tanks from the roof. Replacement of severely oxidized external iron with windows consisting of PVC frames and double glazing. Replacement of external plaster and indoor wall finish. Technical improvement of electrical systems.
The design documents of these renovation works show that no particular attention was paid to the construction and aesthetic details of the original project by Valori. Furthermore, the technical solutions used in the first renovations were replicated without update or revision in the following years, for about one decade, despite the innovative materials and techniques introduced in the building market. Starting in 2001, IACP decided to enlarge the openings on the first floor of the main façades with porticos. This decision aimed to satisfy the necessities of inhabitants, namely increasing the natural lighting and ventilation of the indoor spaces. The architectural impact on the original project, namely the alteration of the geometric composition of the façades, was relevant but neglected, showing that the architectural quality of the project by Valori was not fully recognized.

Recurring Degradations in Cappuccinelli Buildings
Although several works have been updated over time, the current state of the buildings in Cappuccinelli is generally characterized by advanced decay. Many houses are even precarious, as shown by the recent collapse of a portion of the cornice in the portico of block "E".
Appropriate renovation works must be based on a more in-depth analysis of the causes of decay, which can be referred to as a list of recurring phenomena. An analysis of recurring degradations and their related causes was carried out according to what was suggested in [18]. Actually, Nowogońska B. and Mielczarek M. have determined a method for quantification of the cause-effect combinations of deterioration in order to define an order of priority for urgent renovation works and in this sense, the authors have quantified the decay of different Cappuccinelli building elements, focusing on building "L". This is the only block where an original dwelling designed by Valori still exists. The block is also very close to the sea and its façades are particularly exposed to the winds, as compared to the other buildings in the district. Furthermore, renovation works carried out in block "L" are largely documented in the IACP archive. Tables 2 and 3 describe the types of degradation observed in block "L" according to the technical standard UNI 11182:2006 [16,17,20].   A public body (IACP) currently owns seven of the 18 dwellings in block "L" (Figure 4). The only apartment not altered from the project by Valori is owned by a private party and suffers from more severe degradation than the other apartments in the building. Both the geometric and material features of this dwelling have been analyzed.   (Figure 4) of the original plan (the project by Valori) and the southwest elevation of the "L" block and identifies its degradations: plaster exfoliation, plaster erosion, lack of plaster portions, masonry disintegration, masonry erosion, and lack of masonry blocks. In Figure 5b, the extent of each degradation phenomenon is estimated as a percentage of the analyzed surface. Plaster erosion is prevalent (31.9%), while other degradations range from 0.6 to 5.6%. By extending this analysis to the entire "L" block (Figure 6a), erosion is confirmed as the most frequent degradation (4.5%) in all dwellings whose ownership passed from the public subject (IACP) to the private (original renters) (Figure 6b). If the part still owned by IACP is considered (Figure 7a), the most recurrent deterioration is the lack of plaster portions (1.1%) (Figure 7b). More generally, the most frequent degradations on the façades of "L" block involve plasters. Indeed, the materials used for this functional layer were not suitable to calcarenite. Being very porous, this stone easily absorbs marine moisture and its content of salts, accelerating the mechanisms of the observed degradations. The degradations observed in block "L" are recurrent in Cappuccinelli and the information collected through this focus has been used to identify appropriate technological upgrades that could be implemented in large parts of the district both by private and public owners.

Suggestions for Appropriate Deep Renovation
Buildings in the Cappuccinelli district, being close to the sea (about 150 m) and exposed to strong mistral winds, should be equipped with protection systems for reinforced concrete structures in order to significantly reduce the risk of corrosion of the steel reinforcements. However, repairs by the IACP modified the original shape of these building components. As a relevant example, the original shape of the pillars in the porticos (Figure 8a)-a significant architectural detail in the project by Valori-was heavily modified in the renovation works, but their alteration did not make them more effective (Figure 8b). The design of structural strengthening and rehabilitation works, aimed at overcoming the detected causes of damage (presence of rainwater and sea salts; lack of adequate protection for the reinforcement bars; inadequate structural dimensioning) and complying with current requirements for structural safety, also must consider the architectural concept on which the buildings are based. In this sense, archive research on project development and renovation works carried out in Cappuccinelli were essential to complement the in-situ inspection of the buildings in order to identify the original solutions worth being preserved and the inappropriate repairs.
The use of ventilated façades with plaster finishing and/or innovative living walls, discussed in previous works [9,10], can be considered effective solutions for the protection of the façades from the action of atmospheric agents that are particularly aggressive in the environmental context of Cappuccinelli. Their effectiveness has been examined both from environmental and energy points of view.
Ventilated façades prevent atmospheric agents (rain, wind) from damaging the structure, guaranteeing additional protection for the building and limiting metal corrosion, which widely affects the structures of buildings in the district.
Furthermore, if the ventilated façade is realized with plaster finishing (Figure 9), heat flow can be reduced up to about 70% due to the effects of the ventilation [21]. Compared to modular panels, an outer layer made of plaster minimizes the visual impact of the renovation and preserves the urban and architectural features of the buildings. Reduction in surface temperature, a decrease in solar radiation in summer, and the consequent improvement of indoor comfort (mitigation of overheating) are some of the benefits achieved through living walls (Figure 10), which contribute also to noise insulation and air purification. From this point of view, it is worth remarking that the extensive use of vegetation already characterized the original project by Valori, namely by private gardens and trees located in the main inner courtyards. The introduction of vegetation in order to improve energy performance ( Figure 11) has been extensively discussed in previous works [15].

Conclusions
The planning and design of effective building renovations should be addressed through a detailed examination of the physical-mechanical degradations and their causes, together with an analysis of technical and architectural features of buildings. This approach is necessary in the maintenance or refurbishment of social housing districts as well. This stock is often based on interesting architectural and technical solutions that are rarely recognized or frequently altered by both inhabitants and responsible public authorities.
In the Cappuccinelli Social Housing district, inadequate renovation works have merged with a lack of maintenance, social difficulties, and hydrologic vulnerability. On the other side, the architectural quality of the original project and the strategic urban location of this district could be a sensible basis to improve its environmental and social contexts.
The relevance of damages has been inspected also in relation to the ratio between public and private ownership in each block. The main difficulty in standardizing the recovery interventions is linked to the high percentage of apartments sold; in fact, 62% of the apartments are privately owned, while 32% are owned by the IACP. In order to solve this problem, the public body should propose design solutions that are suitable for the energy and architectural improvement of the buildings in close synergy with private individuals in order to uniformly redevelop the entire Cappuccinelli district.
In this study, the physical degradations and anthropogenic alterations of the buildings have been inspected and detailed for two blocks of the district. In addition, the relevance of the damage has been inspected in relation to the ratio between public and private ownership in each block.
The results suggest the relevance of systematic detection and mapping of degradations and alterations in the entire district. Indeed, this information is mainly based on visual, external observation and is able to overcome the difficulties of fragmented ownership.
On the one side, it would be useful to estimate the current structural and energy performances of a dwelling in the district, showing the most critical upgrade measures to implement and highlighting a priority order for urgent renovations. On the other side, by showing recurrent building deficiencies, the systematic analysis and categorization of damages support the identification of effective and replicable solutions to renovate the district buildings and to improve the quality of the urban space.