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Construction Pathology, Rehabilitation Technology and Heritage Management
March 24-27, 2020. Granada, Spain
REHABEND 2020 Congress 1636
CODE 553
ACCEPTANCE OF BUILDING INTEGRATED PHOTOVOLTAIC (BIPV) IN
HERITAGE BUILDINGS AND LANDSCAPES: POTENTIALS, BARRIER AND
ASSESSMENT CRITERIA
Polo López, Cristina S.1*; Lucchi, Elena2; Franco, Giovanna3
1: University of applied sciences and arts of southern Switzerland, Department for environment
construction and design Institute for applied sustainability to the built environment
e-mail: cristina.polo@supsi.ch, web: http://www.supsi.ch
2: Eurac Research, Institute for Renewable Energy
e-mail: elena.lucchi@eurac.edu, web: http://www.eurac.edu
3: University of Genoa, Department of Architectural Design
e-mail: francog@arch.unige.it, web: http://architettura.unige.it
ABSTRACT
The paper refers to the application of Building Integrated Photovoltaic (BIPV) systems for the
renovation of heritage buildings and urban landscapes, preserving their historic, material, aesthetic and
natural values as well as lowering energy bills, increasing comfort, and improving their technical quality
in terms of economic and environmental sustainability. Several criteria for the compatible use of BIPV
systems in heritage context are proposed, also taking into account the perspective of architectural
preservation, legislative framework, research projects, and the scientific literature. The research is
structured in the following steps: (i) examination of existing criteria for acceptable use of BIPV on
heritage sites; (ii) examination of the theory of architectural preservation and restoration; (iii)
identification of a set of criteria for compatible insertion of BIPV; and (iv) assessment of these criteria
on case studies. The study shows new opportunities of inserting new and emerging solar products in
these contexts, especially thanks to the advanced customization possibilities to preserve their values by
resembling other known building materials.
KEYWORDS: BIPV; photovoltaics systems; historic buildings; historic centers; heritage landscape.
1. INTRODUCTION
Improving energy efficiency in historic heritage, preserving their values and characters, is a topic of
great importance, even considering that historic buildings constitute a considerable part of the European
(EU) building stock. The promotion of Renewable Energy Sources (RES) has an important role in this
process, thanks to the Directive 2018/844 has introduced the concept of nearly zero-energy buildings
(NZEBs) [1] for new buildings and for existing buildings subjects to major renovations. Also,
Switzerland moves in this direction. Even if it is not always possible to comply with current energy
standards, it is considered essential trying to improve their energy efficiency as much as possible [2]. At
EU and international level this topic is gaining importance in recent years. Proofs of this increasing
interest is the constant growth of funded project at European level [3; 4; 5; 6; 7; 8]. At international
level, the main aim of the International Energy Agency (IEA) Task 59 [9] is to find conservation-
compatible energy retrofit approaches and technologies for historic (not necessarily protected) buildings
with low energy efficiency and comfort levels, also considering the integration of renewable solar
resources. Different methodologies and decision-making tools to determine the correct approach for
energy retrofitting and management of historical buildings have been investigated so far in EU Research
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Projects [3; 4; 5; 6; 7; 8; 10]. The final aim of most of these projects focused on reducing primary energy
consumptions as much as possible, to improve the level thermal and acoustic conditions, quality of the
internal air and natural lighting conditions, as well as preserving the historic architectural and landscape
values and minimizing the environmental impacts. The aim is to look for a balance between different
needs. Similarly, the International Scientific Committee on Energy and Sustainability within ICOMOS
and the new EU standard EN 16883 set the importance of consider a consensual and uniform approach
to be implemented [11]. The integration between solar energy systems and building components appears
very critical in sensitive historic contexts, especially for the protection of their constitutive materials,
aesthetical appearance and historical values [11]. In the recent past, the installation of photovoltaic (PV)
and solar thermal (ST) systems was not recommendable for historic buildings, to preserve the valuable
fronts and roofs, especially considering traditional PV panels. On the contrary, nowadays, the use of
integrated solar systems within these types of context to enhance energy efficiency becomes increasingly
possible due to the very high compatibility of new products. These products, thanks to advanced
customization with low reflecting and special glasses, colors, patterns and innovative low-cost
treatments, can be designed to appear similar to traditional architectonic materials [13], as already
demonstrated in some research projects [3; 4; 5; 6; 7; 8] and activities carried out within IEA SHC
program [14]. The most popular strategy is the insertion of Building Integrated Photovoltaics (BIPV)
systems into building components, despite the above-mentioned architectural barriers. The integration
of these systems in roofs was studied departing from existing guidelines and less visually intrusive
commercial products [3; 8]. The commitment of local and heritage authorities was introduced as an
important step to find unexplored solutions (i.e. localization on alternative structures close by heritage
sites) [3; 4]. Otherwise, BIPV market is dynamic and characterized by a wide spectrum of new
architectural products for [15; 16]. These products are suitable for the application in heritage context
with minor alterations of the original integrity or harming the aesthetics or cultural value of roofs,
facades, skylights and windows [8; 13; 15; 16; 17; 18]. The installation of solar technologies in these
sensitive contexts has not a unanimous approval in scientific circles and the motivations could be
different from the point of view of conservatives. The reasons for which being somewhat diverse
[16].Alongside evaluations of a technical-economic nature and considerations relevant to effectiveness
and efficiency, the installation of solar - supplied devices clearly contrasts with the “slippery” project to
safeguard cultural and material values, juxtaposing different weights unlikely to find common ground
[15]. However, a shared framework on the acceptability and compatibility of these products on historical
contexts and sensible landscape is still missing. This depends substantially on multiple meanings that
can be attributed to terms such as integrity, alteration, aesthetic and historical values and in the balance
among aims.
2. AIMS AND METHODOLOGY
The paper aims at proposing a set of shared criteria on the application of BIPV systems for the renovation
of heritage buildings and landscapes, preserving their material, aesthetic, and natural values as well as
lowering energy bills, increasing comfort, and improving their technical quality. On the one hand, it is
possible to evaluate the efficiency and the effectiveness of an energy retrofitting intervention from the
quantitative point of view (in terms of energy and economic savings). On the other hand, it is more
difficult to express an assessment from a qualitative point of view, especially in the case of listed
building. The assessment of these interventions should take into consideration how much is lost, in terms
of material culture and historical value, and how much is gained, in terms of energy improvements and
sustainability, as well as perceptive impacts on buildings contexts and landscapes. However, material
loss and energy saving are two entities that are difficult to measure among themselves. It is therefore
necessary to overcome this dichotomy recurring to a systemic approach that could optimize and not
maximize one system over the other. The methodology is based on the literature review, the comparative
analysis of technical legislation and the proposition of a set of quantity-quality criteria. While the
comparative analysis of legislative framework is rather simple, more difficult is the formulation of a set
of shared criteria for the compatible use of BIPV on historic buildings and urban landscapes. It was
therefore necessary to open a light on different philosophies and methodologies to approach architectural
conservation and restoration. The research is structured in the following steps: (i) examination of
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existing criteria for acceptable use of BIPV on heritage contexts in the legislative framework; (ii)
examination of the point of view of architectural restorers and conservators; (iii) identification of a set
of criteria for compatible insertion of BIPV with particular attention to visual impacts; and (iv)
application of these criteria on case studies.
3. CRITERIA FOR COMPATIBLE BIPV APPLICATION
3.1. Criteria from the legislative framework
EU and Switzerland legislations emphasize the key role of combining energy efficiency and RES
integration in the building sector. RES are mandatory for the retrofit of existing buildings, providing
correct inclination and orientation [1]. This measure is not mandatory for listed buildings, when it can
have an impact on the aesthetic value of the building [1]. Important building renovations (in terms of
surfaces involved or energy consumption reduced) require a coverage of 50% for the energy produced
for domestic hot water, heating and cooling through RES [1]. It should also be noted that these energy
sources are one of the requisites needed for the achievement of the Nearly Zero Energy Buildings [1].
In general, the integration of BIPV in the landscape is encouraged reducing its aesthetical impact and
without ruin the heritage structures or natural sites [1]. The systems must be coplanar to the roof, not
protrude, and present a compact shape with a low rate reflection. Several EU Countries defined national
guidelines that include BIPV installation in sensitive buildings and landscapes [1]. Specificity, the
guidelines suggests several examples of best practices, but only in few cases specific aesthetic or
technical criteria for their assessment. Heritage authorizations are mandatory for RES installation on
cultural heritage, particularly for historical and rural buildings, historical towns and settlements, areas
of landscape protection. In this case the final advice of the Heritage Office for Cultural Heritage is
required. As stated, legislative framework in the different countries could approach the topic in a
different way. Nowadays, the authorities and the legal entities are taking positions with a more open-
mind approach. Initially, they established basic criteria and guidelines to respect. Recently, the tendency
is to greater permissibility, pushing to municipalities in searching appropriate and compatibility
solutions with the landscape and constructive characteristics of the urban areas and analysing specific
and singular cases in detail, when necessary. Furthermore, some important methodological premises lie
at the basis of these reflections. This situation is evident also from technical recommendations: (i) to
ensure the maximum material preservation it is preferable to intervene on traditional buildings if quite
degraded or in state of collapse, where completely new roofing is required; (ii) to minimize the alteration
to a landscape it is desirable to intervene on shelters, arbours, service access volumes annexed to the
buildings rather than on buildings which fully embody traditional characteristics; (iii) in urban
landscape, it is preferable to intervene on buildings already compromised by blatant, modifying stages
or on recent buildings, in which materials and building techniques are often employed already different
from traditional architecture regulations [19].
3.2 A common ground for discussion: multiple attitudes in architectural preservation and
restoration
Sustainability and historical heritage, both material and immaterial, seem to belong to increasingly
tangent (and interactive) spheres. This new condition may contribute to overturn cultural reference both
in terms of technical attitude and conservation/restoration principles. Since more than two Centuries,
Europe is discussing about the fate of an impressive amount of ancient monuments, of poor but
meaningful buildings, of urban fabrics and of rural hamlets that survived from the past and still
characterize our territories and built landscapes [20]. During the XIX century, the two recognized
‘fathers’ of the modern restoration theories elaborated two opposite ideas about the attitude to be adopted
in relation with the traces of the past that still influence our debates. Eugène Emmanuel Viollet-le-Duc
clearly declared that restoration was a modern word for a modern thing and that “[…] restoring it is not
preserving a building, but it could mean to bring it again to a state of wholeness that could have never
been existed in a given moment” [21]. With a completely different approach, but agreeing on the modern
essence and origin of the problem, John Ruskin asserted that “[…] restoration is a lie; the worst lie
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which is accompanied by the destruction of the beloved artefact accompanied by the fake description of
the destroyed thing” [22]. Nowadays all over Europe it is possible to identify more or less codified
theoretical-doctrinal positions in accordance with Ruskin’s or Viollet’s thoughts, synthetized in the
following points: (i) the so named “stylistic restoration”, focussed on the construction of a “history of
styles”, by selecting those parts of a monument that are considered consistent with the prevalent
architectural language recognized in the building; (ii) the presumed “philological restoration” [23]
recognized the essence of the monument considered as a document and stated the necessity to valorise
all the signs of succeeding phases of its history; (iii) the so-called “critical and creative restoration”
[24], that implies the critical identification of the outstanding aesthetical values of a monument, its ‘true
form’ as the result of a genius’s creation. A parallel and more complex version of this approach brought
afterwards to the fundamental definition of the treatment of the so-called lacunae, i.e. the voids existing
within a figurative texture, in order to re-establish not the original and lost unity but only the potential
one, still suggested by the survived and remaining parts of the masterpiece of art and thus deciding which
instance should prevail between the historical and the aesthetical one [25]. Finally, (iv) the usually
identified as the modern “preservative approach” gave then the greatest relevance to the permanence of
the existing artefacts, recognised and accepted in their irreducible complexity and contradictoriness,
with no aspiration in transforming the existing buildings to match a coherent idea of them but trying to
safeguard all the past interpretations already embedded in the body of the monument and the possibility
for future ones [20]. In order to be effective in the safeguard of this legacy, we should overcome the
simple struggle between the extreme terms of the traditional debate. If the choice of ‘how’ to intervene
on existing buildings is a matter of decision, we must assume all the responsibilities about it, renouncing
to invoke metaphysical or legal reasons in order to diminish the role we play in determining the real
impact of our ideas and proposals. [26]. Material conservation, minimization of impacts, protection of
the landscape are the indispensable objectives of any new intervention. Whatever the attitude to critical,
stylistic or conservative restoration we can identify criticalities connected to impacts on historical,
landscape and environmental context, substantially summed up below: (i) visible intrusion, given
recipient chromatic characteristics, their shape, reflecting surface (generally contrasting with
morphological surfaces, matter and already existing colours); (ii) modification of soil structure, minute
territorial soil formation, vegetation etc.; (iii) replacing of existing materials and loss of matter
characteristics in traditional architectural presence; (iv) alteration of social perception of the places. On
these critical points, together with the results of previous investigation on legislative framework, the
identification of acceptable criteria could be based [19].
3. IDENTIFICATION OF A SET OF CRITERIA AND BIPV APPLICATION IN CASE
STUDIES
The compatibility criteria for architecture and landscape safeguarding, considering factors affecting the
visibility and impacts, could be sub-divided into: (i) “localizing” (focusing on territorial vocations,
panoramas, building and morphological characteristics of the network but also on the real conditions of
minor building preservation); (ii) “quantitative” (depending on whether it is a question of isolated
systems or repeatable/groupings, considering, hence, the question of scale, with implications for the so-
called cumulative factor); and (iii) “qualitative” (relating to the morphology of the device, its colour, the
possibility to mitigate on the visual impact). The factors affecting “quantity” (surface extent, rapport
with roof, width, height and slope) and “quality” type (shape in relation to the context, colour, texture,
anchoring, arrangement and alignment) are closely interdependent. Hence, compatibility criteria must
be read not so much, and not only, as an independent but as an integrated method as they take into
consideration principally the type of context and its visibility [26]. The first principle in evaluation of
intervention admissibility is the maximum surface extension of the panels on the roof. Roofing rapport
limit (surface of pitched roof/surface of panels) common to most technical regulations is 40% but there
are specific situations with a lower degree of tolerance (15%), with the further indication of the option
of covering only one slope. In small isolated or grouped rural buildings, considering the narrow
dimension of their roof, a dimensional relationship contained to respect 40% would reduce the surface
available for panel installation to limit an energy production – in short totally ineffective! It is, hence,
not unthinkable to propose integrated solutions covering the whole pitched roof, with careful reflection
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on employable materials, colour and panel shape, the way they are positioned, aligned and anchored,
criteria all of a quality nature and, therefore, more difficult to classify. Example of maximum surface
extension interventions are shown in Figure 1 and 2. In any case, elements of a quantity nature are to be
evaluated alongside “scale” and the cumulative effect issuing from repeated intervention on the
landscape, the latter causing greater alteration detection and upsetting proportion equilibria. Effects of
cumulative interventions are shown in Figure 3. As concerns shape, the arrangement of solar panels on
triangular pitched roofs approaches the critical; the roofs poorly adapt to the fixing of a device, or a
group of devices of generally rectangular shape. Consequently, panel-laying may be incompatible,
unless geometrically adaptable shaped panels are employed (“laser cut”); in the case of covering the
entire roof, be it triangular or rectangular, a fringe band of traditional roof covering could opportunely
be left intact. The market today boasts different materials (rigid or flexible panels) and colour schemes
(coloured panes, semi-transparent panes of glass) which constitute a valid alternative for better landscape
compatibility versus traditional photovoltaic panel – the drawback being slow performance and high
cost (Figure 4).
Figure 1: Example on solar BIPV integration in a Glaserhaus, built in 1765 in Affoltern in the Emmental / BE
(CH). Left picture shows the front view of the house from 1765, in the last decades mostly uninhabited before
the renovation. Right picture the illustrates the Plus Energy renovated building using BIPV solar technology in
the roof, where tradition, modernity, sustainability and aesthetics complement each other and significantly
improve the urban landscape (Source: Swiss solar prize 2016 and SUPSI-BFE database)
Figure 2: The 1939 built residence Villa Carlotta in Orselina / TI (CH), was recently renovated. The old oil
heating has been replaced with a 38 kW heat pump solar-powered (BIPV in roof) with six geothermal probes
ranging from 140 to 165 m in depth. The entire 350 m2roof area was equipped with a 51 kW PV system which
covers the total energy requirement 87% (Source: Swiss solar prize 2018)
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Figure 3: MFH-Multi-Family House, SanierunG Feldbergstrasse 4+6 BS (CH). Refurbishment of two houses in
the protected area of Basel-Stadt. The solar roof on the south side provides more energy than is necessary for
heating and hot water (Source: Swiss solar prize 2009, Viridén+Partner AG Zurich)
Figure 4: The Ecuvillens / FR (CH) rural house pilot project, dating back to 1859, uses clay-colored modules
developed by the CSEM and Issol for sites protected by cultural heritage (Source: Swiss solar prize 2018)
The arrangement of the panels in relation to the lay of the pitched roof is another factor to be considered
carefully. As to simple overlapping, it is preferable to select solar device integration with the roof surface
material of the whole pitch, made possible in intervention of complete reroofing. To permit roof
visibility, on the edges of the roof it is advisable to retain a fringe surface strip in traditional material. In
the case of partial pitch covering, another delicate factor affecting the intervention impact is the method
of panel grouping and aligning: care for detail, especially at the junction between panels and roof
covering, remains indeed one of the most delicate aspects in relation to intervention detection.
The application of fortuitous and irregular types should be avoided in favour of solutions retaining or
improving the building’s proportional status freeing, for example, the part of the roof nearest the eaves
and assembling the panels close to the ridge - even if this might contradict some of the technical canons
examined. Co-planarity of the panels to the pitch, referring to alignment, regular shape, grouping and
precision in integrated installation, is another point for roofing panel interaction. When, in the case of
total surface reroofing, elements of small dimensions are chosen (tiles or solar curved tiles, for example)
other factors to be considered besides efficiency (certainly less so than in the case of panels) are the type
of material and texture, in keeping with the method of solar element laying (Figures 5; 6). Available
pitch surface area certainly affects the quantity of the solar or photovoltaic product to be laid and,
consequently, visibility or mimesis; technology, moreover, is making great strides towards the almost
total invisibility of solar cells.
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Figure 5: The refurbishment and addition of new building in the Doragno Castle, Rovio / TI (CH). It uses a BIPV
on the roof (16’000 kWh/y), testing an innovative and sustainable solutions for multifunctional building
envelope to achieve NZE standard, using ST and PV modules (Source: deltaZERO SA Architects, pictures
Luciano Carugo)
Figure 6: Hotel des Associations, Neuchâtel / NE (CH). The building is located in a ISOS protected area. Based
on special and opaque modules, it integrates perfectly with the entire roof surface and preserves the historic
character of the building (Sources: Swiss solar prize 2015).
4. CONCLUSIONS
A first analysis where made to identify compatibility criteria for architecture and landscape
safeguarding, when integrate solar systems in heritage buildings or in protected urban landscapes,
considering factors affecting the visibility and impacts. In parallel, in the growing sector of sustainable
architecture, solar energy represents one of the main challenges that are progressively changing the
building sector with the tangible revolution of solar architecture. The possibilities of new and emerging
solar products, unfortunately not yet well-introduced in the market, thanks to the advanced
customization possibilities (for example, low-reflection and special glasses, colors, patterns, different
shapes and sizes) will offer new opportunities to better insert into contexts of special heritage protection
buildings to preserve their cultural and essential values.
ACKNOLEDGMENT: The research has been co-financed by the European Union (Fondo Europeo di
Sviluppo Regionale), Stato Italiano, Confederazione elvetica and Cantoni, in the Cooperation Program
Interreg V-A Italia-Svizzera for the Project “BIPV meets history. Value-chain creation for the building
integrated photovoltaics in the energy retrofit of transnational historic buildings” (ID n. 603882). The
authors wish to express their gratitude to the IEA SHC and EBC Executive Committees for supporting
the Task59/Annex76.
5. BIBLIOGRAPHY
[1]European Parliament (2018) Directive (EU) 2018/844 of the European Parliament and of the Council
of 30 May 2018 amending Directive 2010/31/EU on the energy performance of buildings and Directive
2012/27/EU on energy efficiency (Text with EEA relevance), Official Journal of the European Union.
[2]European Committee for Standardization (CEN), EN16883:2017 – Conservation of Cultural
Heritage. Guidelines for Improving the Energy Performance of Historic Buildings, British Standard
Institution; Brussels, Belgium, 2017.
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[3]3ENCULT- Efficient Energy for EU Cultural Heritage, http://www.3encult.eu (accessed:
15/07/2019).
[4] EFFESUS: Energy Efficiency for EU Historic Districts’ Sustainability. Seventh Framework
Programme, http://www.effesus.eu/ (accessed 15/07/2019).
[5] RIBUILD: Robust Internal Thermal Insulation of Historic Buildings, http://ribuild.eu/ (accessed
15/07/2019).
[6] Co2ol Bricks: Climate Change, Cultural Heritage & Energy Efficient Monuments,
http://www.co2olbricks.eu/index.php?id=43 (accessed 25/’6/2019).
[7] SECHURBA: Sustainable energy communities in historic urban areas,
http://www.itabc.cnr.it/progetti/sustainable-energy-communities-in-historic-urban-a (accessed
25/06/2019).
[8] BIPV meets history. Value-chain creation for the building integrated photovoltaics in the energy
retrofit of transnational historic buildings” www.bipvmeetshistory.eu (accessed 13/10/2019).
[9] IEA-SHC Task 59, “Deep renovation of historic buildings towards lowest possible energy demand
and CO2emission (nZEB)”, http://task59.iea-shc.org (accessed 03/07/2019).
[10] C. S. Polo López, Francesco Frontini, Energy Efficiency and Renewable Solar Energy Integration
in Heritage Historic Buildings, Energy Procedia, 48 (2014) 1493-1502.
[11] EN 16883:2017: Conservation of cultural heritage. Guidelines for improving the energy
performance of historic buildings.
[12] F. Roberti, U. Filippi Oberegger, E. Lucchi, A. Gasparella, Energy retrofit and conservation of built
heritage using multi-objective optimization: Demonstration on a medieval building, Building Simulation
Applications (2015) 189-197.
[13] I. Zanetti, M. van den Donker et al. (2017). Building Integrated Photovoltaics: Product overview
for solar building skins. Status Report 2017 SUPSI-SEAC, SUPSI, University of Applied Sciences and
Arts of Southern Switzerland, Lugano, Switzerland, available at
http://www.bipv.ch/images/Report%202017_SUPSI_SEAC_BIPV.pdf (accessed 29/11/2017)
[14] IEA Photovoltaic Power System ProgrammeTask 15: Enabling Framework for the Acceleration of
BIPV. PVPS, IEA (2018). Task 15: BIPV: Coloured BIPV: Market, Research and Development.
[15] A. Kumar Shukla, K. Sudhakar, P. Baredar, Recent advancement in BIPV product technologies: A
review, Energy and Buildings 140 (2017) 188-195.
[16] K. Kooles, P. Frey, J. Miller, Installing solar panels on historic buildings. A Survey of the
Regulatory Environment, Technical Report, 2012.
[17] L. F. Cabeza, A. de Gracia, A. L. Pisello, Integration of renewable technologies in historical and
heritage buildings: A review, Energy & Buildings 177 (2018) 96-111.
[18] A. Kandt, E. Hotchkiss, A. Walker, J. Buddenborg, J. Lindberg, Implementing solar PV projects
on historic buildings and in historic districts, Technical Report NREL/TP-7A40-51297, 2011.
[19] G. Franco, A. Magrini, Historical buildings and energy. Switzerland: Springer; 2017.
[20] S. F. Musso, Conserving–Restoring for the Future What We Inherited from the Past. In: Franco G.,
Magrini A. Historical buildings and energy. Switzerland: Springer; 2017: 23-44.
[21] E. E. Viollet Le Duc, Dictionnaire raisonné de l’architecture française du XI au XVI siècle. Paris;
1854-1868.
[22] J. Ruskin, The seven lamps of architecture. London; 1849).
[23] G. Giovannoni, ll restauro dei monumenti, Roma: Cremonese; 1931.
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[24] R. Bonelli, Restauro – restauro architettonico. In Enciclopedia Universale dell’Arte, XI. Venezia-
Roma; 1963.
[25] C. Brandi, Teoria del restauro. Torino: Einaudi; 1977.
[26] G. Franco, Solar powered energy and eco-efficiency in a UNESCO site. Criteria and
recommendations for the National Park of Cinque Terre, Italy, Energy and Buildings 174, 2018, 168-
178.
