Green Systems Integrated to the Building Envelope: Strategies and Technical Solution for the Italian Case

sustainability

Article Green Systems Integrated to the Building Envelope: Strategies and Technical Solution for the Italian Case

Giovanni Santi 1,* , Angelo Bertolazzi 2 , Emanuele Leporelli 1 , Umberto Turrini 2 and Giorgio Croatto 2

1 Department of Energy, Systems, Territory, and Constructions Engineering, University of Pisa, 56122 Pisa, Italy; [email protected] 2 Department of Civil, Environmental and Architectural Engineering, University of Padua, 35131 Padua, Italy; [email protected] (A.B.); [email protected] (U.T.); [email protected] (G.C.) * Correspondence: [email protected]; Tel.: +39-050-221-7776

Received: 4 May 2020; Accepted: 3 June 2020; Published: 5 June 2020

Abstract: Green roofs and green and living walls are increasingly seen in cities, because they are an important strategy that addresses some key urban environmental issues and allows the achievement of different benefits. Among these, the most relevant ones are reduction of the “Urban Heat Island” effect, of rainfall contributions to the sewer system, of environmental impact and energy saving, and retention of harmful substance. The study aims to analyze different systems of greenery systems integrated (GSI), green roofs (GR), and green and living walls (GW-LW), as a possible retrofit technique of the envelope of heritage buildings and especially their applications in the context of historic cities in Italy, pointing out positive and negative aspects. Particularly, it pays attention to the green retrofitting of buildings and to the technical problems related to the installation of systems, since at the moment there are already several studies that show the environmental and microclimatic benefits of the integration of vegetation in architecture. This study tries to highlight the series of design procedures necessary both in the preliminary phase and then in the executive phase to relate the GSI to the existing building envelopes. The GR, from the results of the simulations conducted, demonstrate a greater simplicity in their construction, with improvements also from the point of view of the working loads on the existing structures, since the interventions are performed more easily than those on the facade. The study highlights the architectural needs that are not always considered such as the increase in the thickness of the roof and the related need to raise its edges, changing the perspective of the building. On the other hand, the GW and the LW show some complexity in their construction because they must deal with facades often rich in decorative elements and where openings affect the assemblage and connection works such as the tinsmiths of the intrados of the openings. It must be taken into consideration the necessity of having to drill masonry, often inhomogeneous, to connect fixings and the problems of stability this entails must be carefully analyzed.

Keywords: green facades; extensive green roof; retrofit of existing buildings; design tool; cultural heritage buildings; green retrofitting project; green retrofitting tools; real estate fallout

1. Introduction The application of greenery systems integrated (GSI) in architecture, in the green technology ﬁeld, and in particular systems integrated with the building envelope, both horizontal like green roofs (GR), or vertical, as green walls (GW) and living walls (LW), can be found more often in new constructions. They are sometimes considered as retroﬁt instruments for existing buildings. With the latter application they can contribute to improving the environmental sustainability on both urban and

Sustainability 2020, 12, 4615; doi:10.3390/su12114615 www.mdpi.com/journal/sustainability Sustainability 2020, 12, 4615 2 of 18 architectural scale. That is the reason why they can be considered among the green infrastructures (GI) promoted by the European Commission [1]. Since the first studies in this field, it has been possible to appreciate the positive effects of GR, GW, and LW at Urban Scales, such as the reduction of the Urban Heat Island effect (UHI), the mitigation of the Urban Canyon [2] temperatures, the absorption of the particulates and the noxious substance in the air, the oxygen production and the relative absorption of CO2, in addition to the protection against the erosion due to atmospheric agents and climatic phenomena. The positive effect on single buildings, on thermal dispersion (40% of the Energy Consumption in Europe is absorbed by existing buildings [3]), on the natural cooling of the interiors and exteriors of the building, and the acoustic mitigation of the noises is also significant [4]. This is confirmed also by the results of the energy consumption of the residential and commercial buildings in the United States which in 2016 reached 39.6% of the total usage of the country [5]. In addition to that, it is already certain that green buildings consume about 70% of the energy in comparison with traditional ones [6]. The relation between Green Buildings and efficient energy use in the construction industry is also evaluated by the principal standards such as LEED, Leadership in Energy and Environmental Design (USA), BREEAM, Building Research Establishment Environmental Assessment Methodology (UK), Green Building Label (China), and the Italian standard ITACA. They analyze several parameters: energy, pollution, water, health and wellness, ecology, and waste. Green Buildings are considered the ultimate solution to reduce energy consumption in the construction industry, decreasing gas emissions which cause the greenhouse effect. The application of GSI to buildings produces great thermal, social, environmental, and economic improvements. The objective of this study is to focus on the architectural and executive aspects of the implementation of GSI so that they can be perfectly integrated with the existing building, since we very often pay more attention to the thermal performance of the technological systems than to the construction complexities involved. The application of GSI carries several benefits as a retrofit instrument, though it is not always viable. Since we are taking into consideration an intervention on a pre-existing building, it is necessary to check that:

1. The increase of loads can be supported by the existing structure of the building. 2. Enough space can be found for the increased thickness of roofs and facades. 3. The new envelope may assure the expected performance. 4. Construction elements which can obstruct the implementation of the system be removed or mitigated. 5. Implementation in the pre-existing building of the irrigation plant of the greenery system can be possible. 6. Plant species should integrate with the context, so they must be chosen carefully.

There are several studies which analyze the energetic performance of these systems according to the localization, the plant species implemented, planting substrates, and ecological relevance [7,8]. However, there are studies that analyze the relation between the identity of the building, from an architectural and technical viewpoint, and the features of this kind of system and of their connection elements to the walls. In these conditions a structural evaluation is an essential step during the design process of interventions on existing buildings. In addition to that, also the reversibility of the retroﬁtting interventions is very important to preserve the structural and architectural features of the building [9]. The latter aspects are of fundamental importance in Italy: the state of the art considers the analysis of GSI for buildings—mainly from the second half of the twentieth century—which are often located inside or in the surroundings of historical contexts where the possibility to operate with innovative technologies is somewhat reduced. This paper aims to present a series of technical solutions—tested in two case studies—and general criteria for the installation of "green" systems in the Italian context, Sustainability 2020, 12, 4615 3 of 18 in historic centers, or in areas of architectural value, in which the insertion of new technologies, as well as contemporary architecture, is always very diﬃcult.

2. Materials and Methods Speaking about the retrofitting of existing buildings can appear easy since it is characterized by construction interventions based on dry assembly of several technological elements, but a careful evaluation of possible limitations to plan the strategies which permit to overcome them is needed (Table1). As anticipated in the previous paragraph, it is of considerable importance to define the field of action on the existing building heritage according to the construction period (in relation to both stylistic-architectural and technical-constructive canons) and to the presence of possible conservative limitations (the field of restoration for buildings with historical/landscape implies further verifications to check whether interventions are allowed). It is therefore necessary to confront ourselves with current, Italian local, and national laws and rules, i.e., binding legislation (laws) and voluntary rules (technical standards), in order to verify the legitimacy and the feasibility of retrofitting works [10]. (For example, the Italian scenario, regarding cover and facade works, involves checks in terms of safety and welfare requirements. As safety requirements we highlight: 1.1 Sicurezza strutturale; the structural system must be dimensioned to support the applied loads (permanent, variable, exceptional and seismic loads) ensuring their stability and the ability not to be damaged in order to guarantee the safety of the users. The indications for the dimensioning of the structural elements and the determination of the loads are contained in the D.M. 14 Gennaio 2008 (Norme tecniche per le costruzioni) e nella Circolare n. 617 del 2 Febbraio 2009 (Istruzioni per l’applicazione delle norme tecniche per le costruzioni). 1.2 Sicurezza da caduta di elementi dall’alto; the roofing system must be designed and constructed in such a way that there is no detachment or falling down of elements or parts that may constitute sources of danger to persons or property. It is therefore necessary to adopt special measures so that the design choices can be integrated with the covering mantle, with the protections used for the sliding of the snow, and with the other elements possibly present (downpipes, chimneys, aerials, etc.) and, relatively to bracketing methods and the state of conservation of these. The guidelines for a correct installation and maintenance of these components are provided by technical standards, for example, UNI 9460:2008 (Coperture discontinue—Istruzioni per la progettazione, l’esecuzione e la manutenzione di coperture realizzate con tegole di laterizio o calcestruzzo), UNI 10372:2013 (Coperture discontinue—Istruzioni per la progettazione, l’esecuzione e la manutenzione di coperture realizzate con elementi metallici in lastre), UNI EN 14437:2005 (Determinazione della resistenza al sollevamento di tegole di laterizio o di calcestruzzo installate in coperture—Metodo di prova per il sistema tetto), UNI CEN/TS 15087:2006 (Determinazione della resistenza al sollevamento di tegole di laterizio di calcestruzzo con incastro installate in coperture—Metodo di prova per elementi di collegamento meccanici), or in the codes of good practice developed by the producers of the materials. 1.3 Sicurezza degli interventi; for work at a distance from the ground, above all in roofing, the safety of workers during work must be guaranteed, therefore, a proper access must be provided to the roof, anchorage and protection systems against falls and adequate resistance of the surfaces to loads deriving from workers, equipment and materials according to the following directives, il Decreto legislativo n.81 del 9 Aprile 2008 (Attuazione dell’articolo 1 della legge n.123 03/08/2007, in materia di tutela e della sicurezza nei luoghi di lavoro), UNI EN 795:2012 (Dispositivi individuali per la protezione contro le cadute—Dispositivi di ancoraggio), UNI CEN/TS 16415: 2013 (Dispositivi individuali per la protezione contro le cadute—Dispositivi di ancoraggio -Raccomandazioni per dispositivi di ancoraggio per l’uso da parte di più persone contemporaneamente), UNI 11560: 2014 (Scelta e configurazione dei sistemi di ancoraggio). 1.4 Sicurezza al fuoco, alle cariche elettriche e all’intrusione; the resistance to fire action of technological systems is verified with the UNI EN 1365-2:2014 (Prove di resistenza al fuoco per elementi portanti—Parte 2: Solai e coperture), UNI CEN/TS 1187:2012 (Metodi di prova per tetti esposti al fuoco dall’esterno), UNI EN 1365-1:2012 (Prove di resistenza al fuoco per elementi portanti—Parte 1: Pareti), UNI EN 13381-2:2014 (Metodi di prova per la determinazione del contributo alla resistenza Sustainability 2020, 12, 4615 4 of 18 al fuoco di elementi strutturali—Parte 2: Membrane di protezione verticali), UNI EN 1364-3:2014 (Prove di resistenza al fuoco per elementi non portanti—Parte 3: Facciate continue—Configurazione in grandezza reale—assemblaggio completo), EC 1-2014 UNI EN 1364-4:2014 (Prove di resistenza al fuoco per elementi non portanti—Parte 4: Facciate continue—Configurazione parziale), Guida tecnica su “Requisiti di sicurezza antincendio delle facciate negli edifici civili”, Dipartimento dei Vigili del Fuoco, del Soccorso Pubblico e della Difesa Civile—Direzione centrale per la prevenzione e la Sicurezza Tecnica—Ministero dell’Interno, Marzo 2010.)

Table 1. Logical framework of the problems inherent to retroﬁtting interventions on the existing building heritage.

Problems Intervention Strategies Purposes According to the level of complexity of the building, intervention may increase. A precise Economic sustainability of the Higher costs for the recovery economic evaluation is necessary, even intervention with value verification of intervention resorting to the Value Analysis, in order to the necessary categories of works. determine the cost-benefit ratio of the intervention. Retrofitting interventions can involve both a single building and groups of buildings but also any single intervention, if set in a historical Verifying if the project interventions are Evaluation of the conservative context and conditions and is conditioned by integrated both at an architectural and importance of the historical elements the context. In-depth archival research it is technological level with the that characterize the building. necessary to trace the evolutionary genesis of pre-existent building. the settlement and geometric surveying campaigns in order to know the places and the building itself. Checking the presence of any historical, artistic, archaeological, landscape limitations that could Verification of the presence of any Consistency of the intervention with the affect the area and the single building in the regulatory protection limitations regulations in force. rules that regulate the construction activity in the area involved. The retrofitting intervention must be verified during the design phase so that the achievement of the expected results in terms of energy, environmental, and economic sustainability can be demonstrated. It is Verifying the correspondence of the necessary to carry out analyses of the climatic Verification of the technical feasibility of expected performance of the and environmental context, of the evolutionary the intervention intervention with the history of the building and of the context in project requirements. which it rises, of the building type and of the specific bioclimatic properties, of the materials and construction techniques used, of the thermal performance, and of the static system that connotes the building. The state of the art inherent to the retrofitting interventions both with direct interventions and with numerous case studies and simulations, illustrates the immediate and expected results, the durability and the problems that could arise between pre-existing buildings and new Durability of the intervention over time Poor knowledge of the results obtained intervention. Given the relative recent field of and sustainability of future application, they cannot be clearly determined, maintenance interventions. especially if we think about GSI. In the building dossier it will be appropriate to highlight the need to sample the efficiency of the intervention with pre-established deadlines according to its nature.

Regarding the roofing it is necessary to guarantee an adequate resistance to the passage of electric charges due to lightning or electric current thanks to the correct design of the constituent technical elements which must not allow possible accidental spills, so as not to constitute a risk for people and things as reported in the CEI EN 62305 standards (Lightning protection). As for wellness requirements, we highlight: 2.1 Benessere igrotermico; the values of the thermal transmittance of the building envelope must be verified according to L. 09/01/1991 n. 10, “Norme per l’attuazione del Piano energetico nazionale in materia di uso razionale dell’energia, di risparmio Sustainability 2020, 12, 4615 5 of 18 energetico e di sviluppo delle fonti rinnovabili di energia”; a check in terms of control of the formation of condensation between the constituent layers and in correspondence of the thermal bridgesSustainability according 2020, to12, UNIx FOR PEER 7891 REVIEW (Materiali isolanti—Determinazione della conduttività termica3 of 19 con il metodo dei termoflussimetri).The 2.2retrofitting Benessere intervention acustico; must noise be verified control towards indoor environments according to DPCM 5 Dicembreduring 1997 the (Requisitidesign phase acustici so that the passivi achievement degli edifici), UNI EN ISO 140-14:2004 (Acustica—Misurazione in laboratorioof the expected dell’isolamento results in terms acusticoof energy, di edifici e di elementi di edificio). environmental, and economic sustainability can 2.3 Requisiti di salvaguardia ambientale; regarding to the impact, for example,Verifying of the covering on the be demonstrated. It is necessary to carry out Verification of the correspondence of the environment, energy consumptionanalyses must of the be climatic limited and bothenvironmental in winter and in summer. This is possible technical feasibility expected performance of by guaranteeing the values ofcontext, thermal of the transmittance evolutionary history over of time the as indicated in the standards and of the intervention the intervention with the building and of the context in which it rises, of maintaining the values of temperature and relative humidity compatibleproject with requirements. the activities carried the building type and of the specific bioclimatic out within the buildings, as aproperties, reference of the the materials D.lgs. and n. construction 192 del 19 /08/2005 (Rendimento energetico nell’edilizia); UNI EN ISO 6946:2008techniques used, (Componenti of the thermal edperformance elementi, and per edilizia—resistenza termica e trasmittanza termica—Metodoof the di calcolo).static system 2.4 that Requisiti connotes the di funzionamentobuilding. e gestione; the regulatory framework in Italy sees as theThe first state referenceof the art inherent standard to the forretrofitting the issue of building maintenance and interventions both with direct interventions and management the D.lgs. n. 163with del numerous 12/04/2006 case (Codice studies and dei simulations, contratti pubblici relativi a lavori, servizi e forniture in attuazione delle direttiveillustrates 2004 the immediate/17/CE e and 2004 expected/18/CE), results, the Regolamento attuativo del D.P.R n. 554 del 21 dicembre 1999. Manualthe durability and maintenance and the problems program that could are arise closely relatedDurability tools of that the are necessary between pre-existing buildings and new intervention over time in the variousPoor knowledge phases of of design, construction, operation and re-use of the building. 2.5 Requisiti dei intervention. Given the relative recent field of and sustainability of the results obtained singoli elementi, componenti eapplication, materiali; they numerous cannot be references,clearly determined, we highlight future the maintenance European Community Directive UEAtc for the agreementespecially of if we waterproofing think about GSI.systems, In the building since it is ainterventions. decisive element for the realization of facade screens anddossier new it will covering be appropriate layers.) to highlight the need to sample the efficiency of the intervention 3. The Case Study with pre-established deadlines according to its nature. The results obtained through cognitive intervention strategies (Table1) allow an initial assessment about3. the The feasibility Case Study of the application of GSI to existing buildings. In fact, through critical historical analysis ofThe the results phases obtained of geometric through and cognitive structural intervention surveying, strategies of the deteriorating (Table 1) allow state, an initial and of the static andassessment mechanical about the properties feasibility of of thethe structuralapplication andof GSI material to existing components, buildings. In itfact, is possiblethrough critical to describe the historical-environmentalhistorical analysis of the phases characteristics of geometric ofand the structural building surveying, under of examination the deteriorating and state its, degreeand of conservation,of the static the and type mechanic of usersal properties to which itof isthe intended structural (public, and material private, components, and age it groups—especially is possible to describe the historical-environmental characteristics of the building under examination and its with a view to choosing suitable plant species, it is important to verify any allergens or possible degree of conservation, the type of users to which it is intended (public, private, and age groups— toxicities),especially the with time a of view the to functions choosing suitable performed plant inspecies, the building, it is important and to its verify physical-typological any allergens or and historicalpossible characteristics toxicities), the [11 time,12]. of the functions performed in the building, and its physical-typological Theand experimentationshistorical characteristics were [11 conducted,12]. through two examples that are significant of the Italian construction,The especiallyexperimentations of the secondwere conducted half of thethrough twentieth two examples century, that which are significant we can find of the in ItalianItalian cities. The twoconstruction, experimentations especially areof the simulations, second half of respectively the twentieth for century, the laying which of we a can model find ofin Italian LW (vertical cities. turf) on a concreteThe two experimentations block wall (Figure are1 simulation) and of as, GR respective systemly (extensivefor the laying green of a model roof withof LW low (vertical thickness turf) and on a concrete block wall (Figure 1) and of a GR system (extensive green roof with low thickness and weight) on a concrete and masonry roofing system (Figure2). weight) on a concrete and masonry roofing system (Figure 2).

Figure 1. Existing walling bricks, built in 2008, of a nursery garden greenhouse near Pisa. Initial steps in the installation of the hooks of the living walls (LW). Sustainability 2020, 12, x FOR PEER REVIEW 4 of 19

SustainabilityFigure2020, 1.12 Existing, 4615 walling bricks, built in 2008, of a nursery garden greenhouse near Pisa. Initial steps 6 of 18 in the installation of the hooks of the living walls (LW).

FigureFigure 2. Existing 2. Existing roof, roof, both both ﬂat flat and and inclined, inclined, ofof a building dating dating back back to the to the1960s, 1960s, hosting hosting a study a study room,room, University University of Pisa. of Pisa.

RegardingRegarding the the cognitive cognitive phase, phase, especially as asregards regards the interventions the interventions that involve that involvea limited apart limited part ofof the the building, building, the the legislation legislation [13] [13 allows] allows one one to to carry carry out out structural structural verifications verifications limited limited to the to the elements affected by the intervention and to those on which they directly impact. These checks on elements affected by the intervention and to those on which they directly impact. These checks on the the structural safety level determine if the building function can continue without further structural safety level determine if the building function can continue without further improvement or improvement or if it needs to be modified, for example, by downgrading, change of destination, or if it needslimitations to be ofmodified, use; this for is example, particularly by evident downgrading, above all change in case of of destination, interventions or involvinglimitations the of use; this isimplementation particularly evident of GR on above existing all roofs in case with of the interventions increase of working involving loads the of implementationthe structure. of GR on existing roofs with the increase of working loads of the structure. 3.1. Analysis of the Technological Components of the Building 3.1. Analysis of the Technological Components of the Building In this phase we analyze all the technological components that characterize the building, and in Inparticular, this phase its envelope we analyze and therefore all the technological everything that components interacts with that the characterize external environment, the building, and instudying particular, the individual its envelope technological and therefore units [14] everything to determine that the interacts potentials with and the limits external of the historical environment, studyingbuilding, the individualcarrying out technological precise investigations units [14 regarding] to determine the whole the enclosure potentials and and more limits specifically of the historical the stratigraphy of the external cladding in its opaque and windowed parts and of the roofing. This will building, carrying out precise investigations regarding the whole enclosure and more specifically the be necessary for GW and LW in order to evaluate the most suitable fastening systems to masonry and stratigraphy of the external cladding in its opaque and windowed parts and of the roofing. This will for the GR to determine, in addition to the new overloads, also the sealing layers to avoid subsequent be necessaryinfiltrations. for GW The and wall LW of the in order case study to evaluate examined, the most being suitable a homogeneous fastening masonry systems in to blocks masonry of and for theconcrete GR to for determine, its entire indevelopment, addition to did the not new show overloads, difficulties also in the implementing sealing layers the tometal avoid structure, subsequent infiltrations.supporting The the wall LW, of consisting the case studyof aluminum examined, brackets being and a supports homogeneous for the masonryvertical T and in blocks L aluminum of concrete for itsprofiles, entire development,which allow quick did and not easy show installation difficulties of inthe implementing components and the which metal are structure, fastenedsupporting to the the LW,external consisting wall behind of aluminum by stainless brackets steel anchors. and supports However, for in thethe case vertical of historical, T and L uneven aluminum walls, profiles, in whichwhich allow the quick wall andtexture easy is madeinstallation up of several of the componentsmaterials, there and is the which need are to fastened use vertical to supportthe external wall behindprofiles bywith stainless fastenings steel at anchors. relatively However,large distances in the so case that ofunwanted historical, drilling uneven of the walls, walls in is which not the required. The slab of the case study, from the comparison with similar structures around the same wall texture is made up of several materials, there is the need to use vertical support profiles with period, was supposed to be a concrete and masonry roofing system and from the reliefs it was found, fastenings at relatively large distances so that unwanted drilling of the walls is not required. The in its flat part, to be 25 cm thick; the visual analysis allowed us to find the presence of a 1 cm-thick slab ofbituminous the case sheath study, and from a concrete the comparison screed for slopes with similarwith an average structures thickness around of 3 the cm, same in the period,sloping was supposedpitched to part, be a with concrete a variable and masonryinclination roofing from 19° system to 5°, a and thickness from theof 20 reliefs cm and it wasthe same found, sheath. in its flat part,After to be the 25 cmconsiderations thick; the visualconcerning analysis the enclosure, allowed uswe toevaluated find the the presence relative of physical a 1 cm-thick characteristics bituminous sheathof andthe materials, a concrete the screed thermal for transmittance slopes with of anthe average perimeter thickness walls and of the 3 cm,roof inslab, the the sloping age of the pitched part, buildingwith a variable components,inclination the presence from 19 or◦ to absence 5◦, a thickness of interstitial of 20 condensation, cm and the sameand the sheath. type After and the considerationseffectiveness concerning of insulation. the enclosure, we evaluated the relative physical characteristics of the materials,In the complex thermal projects transmittance it is necessary of the perimeterto consider walls how and the presence the roof slab, of GSI the reduces age of summer the building irradiation, especially in Mediterranean climates [15–18] and the relative reduction of problems components, the presence or absence of interstitial condensation, and the type and effectiveness related to the overheating of the building and the control and minimization of thermal stratifications; of insulation. In complex projects it is necessary to consider how the presence of GSI reduces summer irradiation, especially in Mediterranean climates [15–18] and the relative reduction of problems related to the overheating of the building and the control and minimization of thermal stratifications; all of this must always be related to the possible presence of the decorative apparatus which must not be ignored (Figure3). Sustainability 2020, 12, x FOR PEER REVIEW 5 of 19

all of this must always be related to the possible presence of the decorative apparatus which must not be ignored (Figure 3). For the roofing system, we will consider in addition to its geometry, in pitched inclination terms, the materials that compose it, the type of insulation used to verify the transmittance, and the relative dispersion to the outside; from this part of the feasibility, the GR will result; it can also be integrated into photovoltaic and solar thermal systems. As regards the containment structures, in order to install GW or LW, we must consider the windowed walls and analyze the types of windows (wood, aluminum, PVC, etc.) and glass (simple, double, etc.); not surprisingly, the presence of irrigation systems and of the vegetal mass, entails the Sustainability 2020, 12, x FOR PEER REVIEW 5 of 19 need to put in place special tinsmithing for the protection of the opening intrados (Figure 4). Each material used corresponds to a given transmittance coefficient from which it is possible to all of this must always be related to the possible presence of the decorative apparatus which must determine the corresponding thermal dispersions. Further direct investigations on the oldness ratio not be ignored (Figure 3). of the materials will allow us to determine their energy efficiency and a thermal bridge mapping will For the roofing system, we will consider in addition to its geometry, in pitched inclination terms, thebe performed materials that [19, 20].compose it, the type of insulation used to verify the transmittance, and the relative dispersionThese toexaminations the outside; allow from thethis writing part of theof a feasibilityreport that, the identifies GR will the result; critical it can issues also of be the integrated building with its relative weaker parts from the point of view of energy containment, in addition to the precise Sustainabilityinto photovoltaic2020, 12, 4615 and solar thermal systems. 7 of 18 assessmentAs regards of its theoverall containment energy efficiency. structures, in order to install GW or LW, we must consider the windowed walls and analyze the types of windows (wood, aluminum, PVC, etc.) and glass (simple, double, etc.); not surprisingly, the presence of irrigation systems and of the vegetal mass, entails the need to put in place special tinsmithing for the protection of the opening intrados (Figure 4). Each material used corresponds to a given transmittance coefficient from which it is possible to determine the corresponding thermal dispersions. Further direct investigations on the oldness ratio of the materials will allow us to determine their energy efficiency and a thermal bridge mapping will be performed [19,20]. These examinations allow the writing of a report that identifies the critical issues of the building with its relative weaker parts from the point of view of energy containment, in addition to the precise assessment of its overall energy efficiency.

FigureFigure 3. (Palazzo 3. (Palazzo Agostini Agostini in in Pisa) Pisa) Example Example of a a rooftop rooftop garden garden made made on onan anexisting existing flat roof. ﬂatroof.

For the rooﬁng system, we will consider in addition to its geometry, in pitched inclination terms, the materials that compose it, the type of insulation used to verify the transmittance, and the relative dispersion to the outside; from this part of the feasibility, the GR will result; it can also be integrated into photovoltaic and solar thermal systems. As regards the containment structures, in order to install GW or LW, we must consider the windowed walls and analyze the types of windows (wood, aluminum, PVC, etc.) and glass (simple, double, etc.); not surprisingly, the presence of irrigation systems and of the vegetal mass, entails the need to put in place special tinsmithing for the protection of the opening intrados (Figure4). Figure 3. (Palazzo Agostini in Pisa) Example of a rooftop garden made on an existing flat roof.

Figure 4. (Musée du Quai Branly, Paris) Example of a green façade, equipped with suitable tinsmithing junctions in the points of discontinuity of the façade, such as windows.

FigureFigure 4. (Mus 4. (Muséeée du Quai du Branly,Quai Branly Paris), Paris)Example Example of a green of a façade, green façade, equipped equipped with suitable with suitable tinsmithing junctionstinsmithing in the pointsjunctions of in discontinuity the points of discontinuity of the façade, of suchthe façade, as windows. such as windows.

Each3.2. Analysis material of the used Structural corresponds Components to a of given the Building transmittance coefficient from which it is possible to determineFurther the corresponding direct investigations thermal on dispersions.the oldness ratio Further of the directthe national investigations legislation on in force the oldness NTC 2018 ratio of the materials[21] establishes will allow the general us to determine criteria for theirthe assessment energy effi ofciency safety and and afor thermal the design, bridge execution mapping, and will be performedtesting [ of19 , interventions20]. on existing buildings. Specifically, we introduce the general criteria with Thesewhich examinationsit is possible to allow define the the writing state of of a conservation report that identifies of different the types critical of issues buildings of the and building to distinguish accordingly the types of intervention that can be performed. In confirmation of the with its relative weaker parts from the point of view of energy containment, in addition to the precise assessment of its overall energy efficiency.

3.2. Analysis of the Structural Components of the Building Further direct investigations on the oldness ratio of the the national legislation in force NTC 2018 [21] establishes the general criteria for the assessment of safety and for the design, execution, and testing of interventions on existing buildings. Specifically, we introduce the general criteria with which it is possible to define the state of conservation of different types of buildings and to distinguish accordingly the types of intervention that can be performed. In confirmation of the previous paragraphs, the legislation [22] highlights the importance of conducting specific analyses and surveys to reach an in-depth knowledge of the actual state of the work, in particular: Sustainability 2020, 12, x FOR PEER REVIEW 6 of 19 Sustainability 2020, 12, x FOR PEER REVIEW 6 of 19 previous paragraphs, the legislation [22] highlights the importance of conducting specific analyses previous paragraphs, the legislation [22] highlights the importance of conducting specific analyses and surveys to reach an in-depth knowledge of the actual state of the work, in particular: Sustainabilityand surveys2020 ,to12 reach, 4615 an in-depth knowledge of the actual state of the work, in particular: 8 of 18  if the construction reflects the state of technical knowledge at the period of its construction; • if the construction reflects the state of technical knowledge at the period of its construction;  if there may be unassessed defects in setting and implementation; • if theif there construction may be unassessed reflects the defects state ofin technicalsetting and knowledge implementation; at the period of its construction; •  if the current structures differ from the original ones due to degradation and substantial changes; • if thereif the current may be structures unassessed differ defects from in the setting original and ones implementation; due to degradation and substantial changes; •  if the building subjected to actions, even exceptional ones, whose effects are not completely • if theif the current building structures subjected diff toer actions, from the even original exceptional ones due ones, to degradation whose effects and are substantial not completely changes; • evident. if theevident. building subjected to actions, even exceptional ones, whose effects are not completely evident. • This level of knowledge makes it possible to determine the various structural geometries and This level of knowledge makes it possible to determine the various structural geometries and constructiveThis level elements, of knowledge the permanent makes it agent possible loads to, and determine the mechanical the various properties structural of the geometries materials in and constructive elements, the permanent agent loads, and the mechanical properties of the materials in constructiveorder to apply elements, the use the of structural permanent calculation agent loads, models and for the the mechanical static verification properties of the of intervention. the materials in order to apply the use of structural calculation models for the static verification of the intervention. order to apply the use of structural calculation models for the static verification of the intervention. 3.3. Analysis of the Components of the GR 3.3. Analysis of the Components of the GR 3.3. Analysis of the Components of the GR As reported in the specific regulation [23], the primary items involved in a GR concern As reported in the specific regulation [23], the primary items involved in a GR concern vegetation crops, separation or filtering draining water storage systems, protection against root vegetationAs reported crops, in theseparati specificon or regulation filtering [23draining], the primary water storage items involved systems, in protection a GR concern against vegetation root drops, watertight sealing, thermal insulation, acoustic insulation, and load-bearing elements. The crops,drops, separation watertight or sealing, filtering thermal draining insulation, water storage acoustic systems, insulation, protection and againstload-bearing root drops,elements. watertight The secondary elements could be: ventilation, the vapor barrier layer, the slope layer and the sealing,secondary thermal elements insulation, could acoustic be: ventilation, insulation, the and vapor load-bearing barrier elements.layer, the Theslope secondary layer and elements the regularization layer, and the load distribution layer. The accessory elements of a GR are the irrigation couldregularization be: ventilation, layer, theand vapor the load barrier distribution layer, the layer. slope The layer accessory and the elements regularization of a GR are layer, theand irrigation the load layer or system, those for keeping in place the culture layer; those for securing the draining element; distributionlayer or system, layer. those The accessory for keeping elements in place of the a GRculture are thelayer; irrigation those for layer securing or system, the draining those forelement; keeping anchorage of vegetation; the fire barrier; the inspection little wells and any antifall systems (Figures inanchorage place the cultureof vegetation; layer; thosethe fire for barrier; securing the inspection the draining little element; wells and anchorage any antifall of vegetation;systems (Figures the fire 5–7). barrier;5–7). the inspection little wells and any antifall systems (Figures5–7).

Figure 5. Example of compliant solutions: solution with water storage layer (a) and solution with FigureFigure 5. 5.Example Example of of compliant compliant solutions:solutions: solution solution with with water water storage storage layer layer (a) ( aand) and solution solution with with water storage layer and thermal insulation element (b) (Source image [21]). Legend: 1. vegetation waterwater storage storage layer layer and and thermal thermal insulation insulation elementelement (b) (Source(Source image [21]). [21]). Legend: Legend: 1. 1.vegetation vegetation layer, 2. growing medium, 3. filter layer, 4. water storage layer, 5. drainage layer, 6. root barrier, 7. layer,layer, 2. 2. growing growing medium, medium, 3.3. ﬁlterfilter layer,layer, 4. water water st storageorage layer, layer, 5. 5. drainage drainage layer, layer, 6. 6.root root barrier, barrier, 7. 7. waterproof membrane, 8. Insulation, 9. vapor control layer, 10. slope layer 11. structure. waterproofwaterproof membrane, membrane, 8. 8. Insulation, Insulation, 9.9. vapor control layer, layer, 10. 10. slope slope layer layer 11. 11. structure. structure.

Figure 6. Example of detail of the perimeter border (Source image [21]). Legend: 1. perimeter draining band 2. vertical flap of the root protection element 3. flashing, 4. vegetation layer, 5. growing medium, 6. filter layer, 7. drainage layer, 8. root barrier, 9. waterproof membrane, 10. insulation, 11. vapor control layer, 12. slope layer 13. structure. Sustainability 2020, 12, x FOR PEER REVIEW 7 of 19

Figure 6. Example of detail of the perimeter border (Source image [21]). Legend: 1. perimeter draining band 2. vertical flap of the root protection element 3. flashing, 4. vegetation layer, 5. growing medium, 6. filter layer, 7. drainage layer, 8. root barrier, 9. waterproof membrane, 10. insulation, 11. vapor Sustainability 2020, 12, 4615 9 of 18 control layer, 12. slope layer 13. structure.

Figure 7. RainwaterRainwater col collectionlection and discharge well (Source image [[21]).21]). Legend: 1. perimeter perimeter draining band 2. vertical vertical flap ﬂap of of the the sealing element 3. 3. vegetation vegetation layer, layer, 4. 4. growing growing medium, medium, 5 5.. filter ﬁlter layer, layer, 6 6.. drainage layer, 7.7. root barrier, 8.8. waterproof membrane, 9.9. i insulation,nsulation, 1 10.0. vapor vapor control control layer, 1 11.1. slope slope layerlayer 1 12.2. structure structure..

3.4. Analysis Analysis of of the the C Componentsomponents of of The The GW GW and and LW Two technical alternatives can be implemented depending on on whether the the plants plants are are able to support themselves themselves or or if if they they need need special special supports supports to lean to on lean (Figure on (Figure8). In the 8). ﬁrst In casethe first it is necessary case it is necessaryto pay attention to pay to attention the surfaces to the to whichsurfaces this to natural which coatingthis natural is to becoating applied, is to since be applied, they could since damage they couldthe anchorages damage the of the anchorages plants or the of plantsthe plants could or damage the plants the externalcould damage surface the of the external building. surface The secondof the building.case applies The to second plant speciescase applies that doto plant not have species anchoring that do not organs have and anchoring which need organs support and which structures need supportchosen in structures relation tochosen how theyin relation cling to to the how support; they cling the latterto the mustsupport; be resistant the latter to must stress be and resistant last for to a stresslong time; and last in both for a caseslong time; the plant, in both a creeper, cases the has plant, its roots a creeper, on the has ground its roots and on grows the ground along and the facade.grows alongThen therethe facade. is the solutionThen there with is containers,the solution placed with containers, at a certain placed height, at for a thecertain lodging height, of the for plants the lodging which Sustainabilityofgrow the againplants 2020 spreading which, 12, x FOR grow PEER along again REVIEW the spreading façade, though along onthe special façade, supports. though on special supports. 8 of 19 Systems with modular panels can be classified according to whether they are composed of a groundless textile substrate or are made up of modular cell systems with a substrate made of soil or expanded material. These systems, in which plants grow and are nourished through hydroponic techniques entail a very light weight; however, attention must be paid to the continuous irrigation percolation that could affect the structures behind. For this reason, coating works with low-thickness sheets of the intrados of the openings are also necessary to protect the windows, so that the facade phonometries are not reduced (Figure 9). It is to be observed that maintenance interventions, more complex than those of the GR (given the ground-roof development and often the difficulty of achieving it), involve: plants, with irrigation interventions, fertilization, development guide, fastening to supports and pruning; the brackets to FigureFigure 8. 8.TypesTypes of of vertical vertical green: green: 1 green 1 green walls walls (GW (GW)) green green façade façade with with roots roots on on the the ground ground and and direct direct the support structures, with the control of the stability of the whole structure, the control of the correct developmentdevelopment (Z (Z axis) axis) on on the the façade; façade; 2 2 GW GW green façade withwith rootsroots onon thethe ground ground and and development development on position and the closeness to the wall, and the control of the physical-chemical stability of the onsupports supports along along Z Z axis; axis; 3 3 GW GW green green façade façade with with roots roots at at height height inside inside containers containers and and development development on materials; the enveloping walls, with the control of the mechanical integrity and the chemical stability onsupports supports along along Z axis;Z axis; 4 LW 4 LW living living wall wall system system with with roots roots placed placed at height at height (Z axis) (Z axis) in modular in modular panels of the walls. panelsplaced placed on substructures on substructures ﬁxed fixed to the to walls the walls and plant and plant growth growth orthogonally orthogonally to the to development the development of the offaçade the façade (Y axis). (Y axis).

Systems with modular panels can be classiﬁed according to whether they are composed of a groundless textile substrate or are made up of modular cell systems with a substrate made of soil or expanded material. These systems, in which plants grow and are nourished through hydroponic

Figure 9. Technical construction detail of a LW, with a low thickness and made up of modular panels, placed on existing masonry in correspondence with an opening with the relative works of tinsmithery, with a low thickness, for the coating of the window.

4. Results Considering the installation of the GR above the roof of an existing building, as a retrofit technique, it is necessary to define the working loads in order to carry out a future structural calculation for each specific case study. It will be necessary, indeed, to verify that the structure be able to support the additional strain and to respect the safety required by the legislation [13]. In relation to the experiments carried out, both in the case study of the LW and the GR, it results that the choice must be directed towards a type of intervention that does not seriously affect the existing structure and maintains the present load conditions, both of the wall and of the coverage almost unchanged. Sustainability 2020, 12, x FOR PEER REVIEW 8 of 19

Sustainability 2020, 12, 4615 10 of 18 Figure 8. Types of vertical green: 1 green walls (GW) green façade with roots on the ground and direct development (Z axis) on the façade; 2 GW green façade with roots on the ground and development techniques entail a very light weight; however, attention must be paid to the continuous irrigation on supports along Z axis; 3 GW green façade with roots at height inside containers and development percolation that could aﬀect the structures behind. For this reason, coating works with low-thickness on supports along Z axis; 4 LW living wall system with roots placed at height (Z axis) in modular sheets of the intrados of the openings are also necessary to protect the windows, so that the facade panels placed on substructures fixed to the walls and plant growth orthogonally to the development phonometriesof the façade are (Y not axis). reduced (Figure9).

FigureFigure 9. 9. TechnicalTechnical construction construction detail detail of of a a L LW,W, with with a a low low thickness thickness and and made made up up of of modular modular panels, panels, placedplaced on on existing existing masonry masonry in correspondence in correspondence with withan opening an opening with the with relative the works relative of tinsmithery, works of tinsmithery,with a low thickness, with a low for thickness, the coating forof the the coating window. of the window.

4. ResultsIt is to be observed that maintenance interventions, more complex than those of the GR (given the ground-roof development and often the difficulty of achieving it), involve: plants, with irrigation Considering the installation of the GR above the roof of an existing building, as a retrofit interventions, fertilization, development guide, fastening to supports and pruning; the brackets to the technique, it is necessary to define the working loads in order to carry out a future structural support structures, with the control of the stability of the whole structure, the control of the correct calculation for each specific case study. It will be necessary, indeed, to verify that the structure be position and the closeness to the wall, and the control of the physical-chemical stability of the materials; able to support the additional strain and to respect the safety required by the legislation [13]. In the enveloping walls, with the control of the mechanical integrity and the chemical stability of the walls. relation to the experiments carried out, both in the case study of the LW and the GR, it results that the4. Resultschoice must be directed towards a type of intervention that does not seriously affect the existing structure and maintains the present load conditions, both of the wall and of the coverage almost unchanged.Considering the installation of the GR above the roof of an existing building, as a retrofit technique, it is necessary to define the working loads in order to carry out a future structural calculation for each specific case study. It will be necessary, indeed, to verify that the structure be able to support the additional strain and to respect the safety required by the legislation [13]. In relation to the experiments carried out, both in the case study of the LW and the GR, it results that the choice must be directed towards a type of intervention that does not seriously affect the existing structure and maintains the present load conditions, both of the wall and of the coverage almost unchanged. Sustainability 2020, 12, 4615 11 of 18

In regards to green roofs, light interventions are appropriate, their load being almost exclusively represented by the presence of water in the substrate and in the accumulation and drainage layer. The corresponding GR is the extensive type because it is characterized by reduced thicknesses, the one examined is 16 cm (22 cm including the insulation panel), and is low-weight also thanks to the use of Sedum for the vegetational part: 127 kg/m2 at maximum saturation and 75 kg/m2 at dry conditions, when the water content of the GR, using rainfall data of the area together with the storage and drainage capacity of the panel considered, is equal to 52,16 mm/m2 (kg/m2). These data, when compared with an analysis of the loads of an existing roof consisting of only one layer of slate, usually used in roofs where you cannot walk, show how the removal of the latter (with a weight of about 120 kg/m2), and with the removal of any slope screed (with a weight of about 80 kg/m2) could also allow the subsequent laying of the GR considered keeping the load conditions almost unchanged. The objective of the present study is to highlight the architectural works necessary for the laying of a GR on an existing building, and those emerging in the simulation conducted, that led to the energy and economic assessments not presented here, suggesting a series of technical solutions such as:

Raising of the perimeter edges of the roof. • In the interventions on existing roofs, as shown also in the case study, it is necessary to raise the perimeter edges of the roof, to contain the greater thickness of the stratigraphy, due to the laying of the constructive elements of the GR. Interventions that affect the eaves, ledges, ribs—as in the case studied—become even more complex when we have to work on buildings of a certain historical value, owing to the original construction techniques, think of the delicacy of wooden roofing, and owing to the large decorative apparatus that finds one of the highest expressions in the gutters with finely worked ledges. The simulation, in the case study, provided for a cant of the ribs through the mechanical connection of structures, along the perimeter of the existing structure, to which the new roof flashings can be hooked; they can also be integrated with the existing ledges, all of this can be done keeping in mind the building legislation on the prevention of the risk of falls from a high building. An intervention that can also be extended to flat roofs to make the total height of the building uniform and also to guarantee stability and security requirements.

Disposal of rainwater and irrigation. • The accumulation of rainwater and irrigation, in the cases of both inclined and flat roofing, must consider the proper sizing of the existing downspouts which, if necessary, must be integrated with new ones by intervening on the existing structures, for example on the covering ribs of the case study, creating holes that allow the connection of the covering to the downspouts arranged along the perimeter of the building; in addition to that, in order to allow accessibility and maintenance of the drains, some control wells should be positioned. To realize the horizontal extensive GR of the case study (Figures 10 and 11), the following are applied on the slab: vapor barrier, insulating panel, waterproof and anti-root sheath, modular draining element for the lodging of the plants, filtering cloth, substrate for the plants, and Sedum plant layer owing to its lower weight and low maintenance. In regards to the tilted extensive GR, the case study highlighted the problems that might occur in similar situations when it is necessary to apply it because of precise architectural requirements or environmental reasons (Figures 12 and 13). There is a complexity demonstrated by the added need to give stability and security to the entire sloping system, also allowing the regular disposal of water. Therefore, the roofing requires a very careful design that evaluates in depth the characteristics of the retention systems and of their bracketing—the system considered provides for the use of special plugs that remain retractable within the thickness of the entire package, fastened to the existing underlying structure and waterproofed; a system that still requires improvement in terms of watertightness—and all the particularities of functioning related to the geometry of the pitch and its slope, the drainage of Sustainability 2020, 12, 4615 12 of 18

Sustainability 2020, 12, x FOR PEER REVIEW 10 of 19 Sustainability 2020, 12, x FOR PEER REVIEW 10 of 19 the water, and the type of vegetation. As the inclination increases, there is a consequent increase of drainagemaintenance capacity costs, to because allow ata rapid the base flow of theof the pitch water it is suitableaccumulated to increase to the the drains. drainage The capacitymaintenance to allow of thedrainage extensive capacity GRs isto divided allow a mainlyrapid flow into of three the waterphases: accumulated the completion to the care drains. (up to The a coverage maintenance ratio ofof athe rapid extensive ﬂow of GRs the is water divided accumulated mainly into to thethree drains. phases: The the maintenance completion of care the (up extensive to a coverage GRs is dividedratio of 80%mainly [18] into with three a duration phases: of the approximately completion care 12 to (up 15 to months), a coverage regular ratio start of 80%-up [ 18maintenance] with a duration (follows of the80% completion [18] with a and duration concerns of approximately maintenance until 12 to the 15 functional months), regularstate is reachedstart-up— maintenanceduration from (follows 2 to 4 approximatelythe completion 12and to concerns 15 months), maintenance regular start-up until the maintenance functional state (follows is reached the completion—duration and from concerns 2 to 4 years),maintenance ordinary until maintenance the functional (regarding state is reached—durationthe maintenance of fromvegetation 2 to 4— years),duration ordinary dependent maintenance on the maintenanceyears), ordinary contract). maintenance (regarding the maintenance of vegetation—duration dependent on the (regardingmaintenance the contract). maintenance of vegetation—duration dependent on the maintenance contract). According to ththee necessity and intensity and development of the planting, the maintenance interventionsAccording involve: to the irrigation necessity (priority and intensity in the initial and development phase), weeding of thethe application planting, the of maintenanceslow-release interventionsinterventions involve:involve: irrigation (priority in the initial phase), weeding the application of slow slow-release-release organic or inorganic fertilizer, the reseeding or plant reimplantation, su substratebstrate thickness thickness control, control, cleaningorganic orof covering inorganic edges, fertilizer, drainage the reseeding channels , orand plant inspection reimplantation, of little wells substrate and drains. thickness control, cleaning of covering edges,edges, drainagedrainage channels,channels, andand inspectioninspection ofof littlelittle wellswells andand drains.drains.

Figure 10. Particular existing flat roof: 1 concrete and masonry flooring system, 2 structural slab, 3 Figure 10. Particular existing flat roof: 1 concrete and masonry flooring system, 2 structural slab, slopeFigure screed, 10. Particular 4 waterproof existing sheath, flat roof:5 load 1- bearingconcrete element, and masonry 6 sheeting, flooring 7 flashing. system, 2 structural slab, 3 3slope slope screed, screed, 4 waterproof 4 waterproof sheath, sheath, 5 load 5 load-bearing-bearing element, element, 6 sheeting, 6 sheeting, 7 flashing. 7 flashing.

Figure 11. Detail of flat GR: 1 flooring system, 2 structural slab, 3 vapor barrier, 4 insulation, 5 waterproof Figure 11. Detail of flat GR: 1 flooring system, 2 structural slab, 3 vapor barrier, 4 insulation, 5 anti-root sheath, 6 draining element, 7 filter cloth, 8–9 sedum plant part, 10–11 containment elements, waterproofFigure 11. Detail anti-root of flat sheath, GR: 1 6 flooring draining system, element, 2 structural 7 filter cloth, slab, 3 8 – vapor9 sedum barrier, plant 4 insulation, part, 10–11 5 12–13 grid and control well, 14 rainwater, 15 vault, 16 cant for the perimeter vault with parapet. containmentwaterproof antielements,-root sheath,12–13 grid 6 drainingand control element, well, 14 7 rainwater, filter cloth, 15 vault, 8–9 sedum 16 cant plantfor the part, perimeter 10–11 Thickness 225 mm Dry weight 75 kg/m2 Saturated weight H2O 125 kg/m2. vaultcontainment with parapet. elements, Thickness 12–13 grid225 mmand Drycontrol weight well, 75 14 kg/ rainwater,m2 Saturated 15 vault, weight 16 H2O cant 125for kg/the mperimeter2. vault with parapet. Thickness 225 mm Dry weight 75 kg/m2 Saturated weight H2O 125 kg/m2. Sustainability 2020, 12, x FOR PEER REVIEW 11 of 19 Sustainability 2020, 12, 4615 13 of 18 Sustainability 2020, 12, x FOR PEER REVIEW 11 of 19

Figure 12. Special existing inclined roofing: 1 covering structure, 2 waterproof sheath, 3 sheeting, 4 Figureflashing. 12. Special existing inclined rooﬁng: 1 covering structure, 2 waterproof sheath, 3 sheeting, 4Figure ﬂashing. 12. Special existing inclined roofing: 1 covering structure, 2 waterproof sheath, 3 sheeting, 4 flashing.

Figure 13. Particular inclined GR: 1 covering structure, 2 vapor barrier, 3 insulating, 4 waterproof Figure 13. Particular inclined GR: 1 covering structure, 2 vapor barrier, 3 insulating, 4 waterproof antiroot sheath, 5 draining element, 6 filtering mat, 7–8 substrate and retention system, 9–10 draining antiroot sheath, 5 draining element, 6 filtering mat, 7–8 substrate and retention system, 9–10 draining gravelFigure varies 13. Particular size, 11–12 inclined grid and GR: control 1 covering well, 13structure, raised element 2 vapor of barrier, the perimeter 3 insulating, vault with4 waterproof parapet, gravel varies size, 11–12 grid and control well, 13 raised element2 of the perimeter vault with parapet,2. 14antiroot vault, 15sheath, downpipe. 5 draining Thickness element, 225 6 mm filtering Dry weightmat, 7– 758 substrate kg/m Saturated and retention weight system, H2O 117 9–10 kg draining/m 14 vault, 15 downpipe. Thickness 225 mm Dry weight 75 kg/m2 Saturated weight H2O 117 kg/m2. gravel varies size, 11–12 grid and control well, 13 raised element of the perimeter vault with parapet, Considering vertical systems, the problems concerning the installation of GW and GL on the 14 vault, 15 downpipe. Thickness 225 mm Dry weight 75 kg/m2 Saturated weight H2O 117 kg/m2. facadesConsidering are related vertical to the kindsystems, of facade, the problems even ventilated concerning claddings, the installation fixed to theof GW building and GL structure. on the facades are related to the kind of facade, even ventilated claddings, fixed to the building structure. Specifically,Considering the problems vertical to systems, be verified the andproblems resolved concerning are: the installation of GW and GL on the Specifically, the problems to be verified and resolved are: facadesGeometry are related andinclination to the kind of of structure facade, even andcoating ventilated claddings, fixed to the building structure. • Specifically, AlignmentsGeometry the and andproblems inclination holes forto be windows of verified structure andand and doorsresolved coating are: • Alignments and holes for windows and doors  InterconnectionGeometry and inclination of doors and of windowsstructure withand coating the intrados and facade • Interconnection of doors and windows with the intrados and facade  AcousticAlignments bridges and holes for windows and doors • Acoustic bridges  ThermalInterconnection bridges of doors and windows with the intrados and facade • Thermal bridges  TypeAcoustic and connectionbridges system and internal-external coordination • Type and connection system and internal-external coordination  CollectionThermal bridges and disposal of rainwater • Collection and disposal of rainwater  AssemblyType and andconnection disassembly system flexibility and internal-external coordination • Assembly and disassembly flexibility  Collection and disposal of rainwater  InterfaceInterface withwith otherother subsystems,subsystems, plants,plants, elementselements • Assembly and disassembly flexibility  Interface with other subsystems, plants, elements Sustainability 2020, 12, x FOR PEER REVIEW 12 of 19

 Cleaning of facades and glazed components  Maintenance of cladding and windows Of particular importance for a correct design of the GW and LW are the calculation of the dimensions of the fixings: vegetated-substructure system and substructure-wall building. The case study showed a simple assemblage due to the presence of an external wall with regular texture (Figures 14–18). However, in cases of intervention on historical structures, where there is uncertainty about the construction techniques or the possible plant components inside the partitions that may affect the insertion of fixing systems, a first assessment of the state of the construction could be appropriate through the use of tools that reveal the existing wall texture. The dimensions of the metal substructures, of the support and brackets of the elements conforming the plants, and of the other components of the anchoring system must be calculated according to:  vertical load, with particular reference to the bending moment and to the different states of humidity of the system in case of LW; Sustainability horizontal2020, thrusts,12, 4615 that is the forces of compression and depression of the wind, with reference14 of 18 to the GW, because they consist of climbing green on racks or cables placed on the facade that could tear, and to the LW whose panels could become loose. Cleaning of facades and glazed components • ToMaintenance assess the dimensioning of cladding and of windowsthe whole system, it is therefore necessary to calculate the wind • pressure and depression, determinate the exposure coefficient that depends on the height of the constructionOf particular on the importanceground, the forroughness a correct classes, design the of thermal the GW variations, and LW areto calculate the calculation the air blade of the withdimensions its compartmentaliz of the fixings:ation vegetated-substructure in cases of LW. The system latter and is recommended substructure-wall to be building. implemented, to optimizeThe the case LW study yield, showed with aa simplecompartmentalization assemblage due of to the presenceventilation of anlayer, external using, wall if possible, with regular the profilestexture of (Figures the substructure 14–18). However, of the bracketing in cases system, of intervention otherwise on inserting historical appropriat structures,e flashings. where there This is compartmentalization,uncertainty about the constructionfirst of all, creates techniques a physical or the possiblebarrier to plant the spread components of flames inside or thecombustion partitions productsthat may aresultingffect the insertion from a possible of fixing systems,fire and a makes first assessment the LW an of the advanced state of thetechnological construction system could comparablebe appropriate to ventilated through the facades. use of tools that reveal the existing wall texture.

Sustainability 2020, 12, x FOR PEERFigure REVIEW 14. Design detail of the LW project being tested. 13 of 19 Figure 14. Design detail of the LW project being tested.

Figure 15. TheThe fixing ﬁxing to the the existing existing infill inﬁll is made by a 30/10 30/10 aluminum bracket with clip clamp allows an easy easy and and quick quick implementation; implementation; each eachcomponent component is equipped is equipped with a 60 with/10 polypropylene a 60/10 polypropylene thermostop element,thermostop in blue,eleme tont, avoid in blue, thermal to avoid bridges. thermal bridges.

Figure 16. Insertion of T profiles in 20/10 aluminum, supporting the vegetated panels, inside the brackets.

Figure 17. Detail of the interstitial ventilation chamber between the vegetated panels and the wall structure behind it. Sustainability 2020, 12, x FOR PEER REVIEW 13 of 19 Sustainability 2020, 12, x FOR PEER REVIEW 13 of 19

Figure 15. The fixing to the existing infill is made by a 30/10 aluminum bracket with clip clamp allows Figure 15. The fixing to the existing infill is made by a 30/10 aluminum bracket with clip clamp allows an easy and quick implementation; each component is equipped with a 60/10 polypropylene Sustainability 2020an , easy12, 4615 and quick implementation; each component is equipped with a 60/10 polypropylene 15 of 18 thermostop element, in blue, to avoid thermal bridges. thermostop element, in blue, to avoid thermal bridges.

Figure 16. Insertion of T profiles in 20/10 aluminum, supporting the vegetated panels, inside the Figure 16. Insertion of T profiles in 20/10 aluminum, supporting the vegetated panels, inside the Figure 16.brackets.Insertion of T proﬁles in 20/10 aluminum, supporting the vegetated panels, inside the brackets. brackets.

Figure 17. Detail of the interstitial ventilation chamber between the vegetated panels and the wall Figure 17.FigureDetail 17. Detail of the of interstitialthe interstitial ventilation ventilation chamberchamber between between the thevegetated vegetated panels panels and the and wall the wall structure behind it. structureSustainabilitystructure behind 2020 behind, it.12, x FOR it. PEER REVIEW 14 of 19

FigureFigure 18. The 18. LW,The LW, the objectthe object of of experimentation experimentation and and consisting consisting of modular of modular grassed grassed panels, panels, is is perimetrated by closing sheets of the rear ventilation chamber. perimetrated by closing sheets of the rear ventilation chamber. 5. Conclusions and Future Developments The extensive scientific literature on greenery systems integrated into the building envelope GSI [23], whether GR or GW and LW, illustrates their benefits under various aspects, from energy saving and acoustical to ecological and psychological aspects [24–27], on experimental models, laboratory tests and realizations, very often verifying only the performances of the stratigraphic sections that make up the systems. However, the problems related to retrofitting interventions are still uncertain because the application of GSI also involves other technological works that sometimes go beyond the systems themselves but which are necessary for their correct installation in relation to existing structures. With this in mind, and from the results of the analysis carried out and the solutions verified, this study tries to highlight the series of design procedures necessary both in the preliminary phase and then in the executive phase, to relate the GSI to the existing building envelopes, focusing on the works necessary so that these can be implemented in existing buildings. The GR, from the results of the simulations conducted, demonstrate a greater simplicity in their construction, with improvements also from the point of view of the working loads on the existing structures, since the interventions are performed more easily than those on the facade. It is to be considered, indeed, that the openings on the roofs are normally fewer in number than in a facade with all the positive consequences for possible insulation and connection works. The study, however, highlights the architectural needs that are not always considered such as the increase in the thickness of the roof and the related need to raise its edges, changing the perspective of the building (Table 2).

Table 2. GR methodological framework and intervention criteria guidelines.

Action Instruments Goals Archive documents, direct, Focusing on the materials, geometrical, material, Defining the technological horizon of techniques, and structural, and decay-related the period under survey. construction systems survey Choice of the technological Analysis of regulatory and Admissibility of increase in the system for the GR historical constraints thickness of the roof with the need to Sustainability 2020, 12, 4615 16 of 18

The dimensions of the metal substructures, of the support and brackets of the elements conforming the plants, and of the other components of the anchoring system must be calculated according to:

vertical load, with particular reference to the bending moment and to the diﬀerent states of • humidity of the system in case of LW; horizontal thrusts, that is the forces of compression and depression of the wind, with reference to • the GW, because they consist of climbing green on racks or cables placed on the facade that could tear, and to the LW whose panels could become loose.

To assess the dimensioning of the whole system, it is therefore necessary to calculate the wind pressure and depression, determinate the exposure coefficient that depends on the height of the construction on the ground, the roughness classes, the thermal variations, to calculate the air blade with its compartmentalization in cases of LW. The latter is recommended to be implemented, to optimize the LW yield, with a compartmentalization of the ventilation layer, using, if possible, the profiles of the substructure of the bracketing system, otherwise inserting appropriate flashings. This compartmentalization, first of all, creates a physical barrier to the spread of flames or combustion products resulting from a possible fire and makes the LW an advanced technological system comparable to ventilated facades.

5. Conclusions and Future Developments The extensive scientific literature on greenery systems integrated into the building envelope GSI [23], whether GR or GW and LW, illustrates their benefits under various aspects, from energy saving and acoustical to ecological and psychological aspects [24–27], on experimental models, laboratory tests and realizations, very often verifying only the performances of the stratigraphic sections that make up the systems. However, the problems related to retrofitting interventions are still uncertain because the application of GSI also involves other technological works that sometimes go beyond the systems themselves but which are necessary for their correct installation in relation to existing structures. With this in mind, and from the results of the analysis carried out and the solutions verified, this study tries to highlight the series of design procedures necessary both in the preliminary phase and then in the executive phase, to relate the GSI to the existing building envelopes, focusing on the works necessary so that these can be implemented in existing buildings. The GR, from the results of the simulations conducted, demonstrate a greater simplicity in their construction, with improvements also from the point of view of the working loads on the existing structures, since the interventions are performed more easily than those on the facade. It is to be considered, indeed, that the openings on the roofs are normally fewer in number than in a facade with all the positive consequences for possible insulation and connection works. The study, however, highlights the architectural needs that are not always considered such as the increase in the thickness of the roof and the related need to raise its edges, changing the perspective of the building (Table2).

Table 2. GR methodological framework and intervention criteria guidelines.

Action Instruments Goals Archive documents, direct, Focusing on the materials, techniques, Deﬁning the technological horizon of the geometrical, material, structural, and construction systems period under survey. and decay-related survey Admissibility of increase in the thickness of Analysis of regulatory and Choice of the technological system for the GR the roof with the need to raise its edges by historical constraints changing the perspective of the building. Determining the real (mechanical building Static and dynamic test of the building and In situ and laboratory tests and physical) building’s features correct assessment of general conditions Modeling the existing building in Implementing a virtual model for a ﬁrst test simulated environment: Ad hoc software of the building before, after, and while work B.I.M., H.B.I.M., advanced survey methods is in progress of the GR installation Sustainability 2020, 12, 4615 17 of 18

On the other hand, the GW and the LW, the latter analysed in its application on a newly-constructed existing brick wall, show some complexity in their construction because they must deal with facades often rich in decorative elements and where openings affect the assemblage and connection works such as the tinsmiths of the intrados of the openings. The necessity of having to drill masonry, often inhomogeneous, to connect fixings and the problems of stability this entails, must be carefully analyzed. The energy and environmental advantages, widely analyzed by the studies in progress, are a counterweight to these seeming difficulties that can easily be overcome with the optimization of models of assisted design (B.I.M., H.B.I.M., advanced survey methods) (Table3).

Table 3. GW and LW methodological framework and intervention criteria guidelines.

Action Instruments Goals Archive documents, direct, Focusing on the materials, techniques, and Deﬁning the technological horizon of the geometrical, material, structural, construction systems period under survey. and decay-related survey Choice of the technological system for the GW Analysis of regulatory and Compatibility of the system used with the and LW historical constraints facade of the building. Solution of general problems. Static and Determining the real (mechanical building In situ and laboratory tests dynamic test of the building and correct and physical) building’s features assessment of general conditions On site survey of details, Determining existing wall texture and Solution of punctual problems. Sizing of the thermography, and infrared architectural composition of the facade anchors in relation to the existing structure. instruments. Modeling the existing building in simulated Implementing a virtual model for a ﬁrst test environment: Ad hoc software of the building before, after, and while work B.I.M., H.B.I.M., advanced survey methods is in progress of the GW and LW installation

The intervention criteria and the guidelines, here exposed, for the application of the GSI to the Italian context (materials and construction techniques), also in relation to the context, could be the beginning for the next step of research, for a quantitative veriﬁcation in relation to other possible solutions. However, the scenarios are nevertheless open to experimenting with increasingly technologically ﬂexible GSI solutions, so that they may become a valid tool available to the existing building heritage.

Author Contributions: Conceptualization, G.S., A.B. and G.C.; methodology, G.S., A.B., E.L., U.T. and G.C.; validation, G.S., A.B., U.T. and G.C.; formal analysis, G.S., A.B., E.L., U.T. and G.C.; investigation, G.S. and A.B.; resources, G.S. and E.L.; data curation, G.S., A.B. and E.L.; writing—original draft preparation, G.S., A.B. and E.L.; writing—review and editing, G.S. and A.B.; visualization, G.S. and A.B.; supervision, U.T. and G.C. All authors have read and agreed to the published version of the manuscript. Funding: This research received no external funding. Conﬂicts of Interest: The authors declare no conﬂict of interest.

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