Type of intervention   Restoration X Rehabilitation/Renovation
Concerned elements on the intervention project   1. Foundations and underground structures   5. Façade and building envelope
    2. Vertical structures   6. Finishes and completion elements
    3. Horizontal structures and vertical connections X 7. Integrate services
    4. Roof and terraces X 8. General strategies for building recovery
Reference to the Database 1  




Site/Address Church of San Giovanni Battista (Baptistery), Treviso, Veneto, Italy
Objectives Rehabilitation intervention and energy retrofit
Property Italian Church, Diocese of Treviso, Chapter of the Cathedral and Parish of St. Peter the Apostle into the Cathedral



Arch. Diego De Nardi; Bonazza Construction and Restorations
Date Project 2013-2015; Rehabilitation building yard 2015-2017




Background to the intervention


The particular dialogue between ecclesiastical cultural heritage and facilities has intertwined archaeology and architecture, becoming an unrepeatable opportunity for investigation to add pieces to the history of the artefact, also from an anthropological point of view, as a salient piece of history of the city: involving in the construction phases, close and complex interactions with the Superintendency.


The central aspect of the design methodology adopted consisted in the research for technically correct solutions, adhering to the user’s needs and such as to satisfy the following basic requirements:

a) compliance with technical regulations, general and specific for the particular type of building, in relation to the accessibility of the building complex by the handicapped (design for all), the containment of energy consumption, safety and accident prevention of personnel assigned to prevent the danger of fires, etc .;

b) the reduction, as far as possible, of the physical impact of the integrated services on the building structure of the building, or the formal definition of the technical component (plant) as a qualifying and visible element of the intervention;

c) the use and exploitation of particular volumes and hollow spaces of the building for the creation of technical spaces dedicated to the systems, in compliance with the law and the architectural constraints that the building imposes.




Description of the building


The church of San Giovanni Battista, Baptistery of Treviso, is in pure Romanesque style: the three-light window on the façade and the double arches that mark the external walls (similar to those of the Romanesque ‘fragment’ on the north side of the Duomo), make it go up, as well as the Cathedral, in the eleventh century.

The church, which already underwent a first restoration intervention after 1222, has been remodelled several times: in the Gothic period, in 1531-32, around 1561 (the roof will probably be rebuilt) and at the beginning of the 19th century.

In the fourteenth or fifteenth century houses were built on the northern side and one on the facade (with a portico and demolished in 1815).






The diagnosis of the building (values and state)


Preliminary and preparatory investigations (AUDIT)


The Audit phase includes both energy and thermo-hygrometric evaluations, and more generally, integrated services-type evaluations.

This is an analytical methodological approach, consisting of a long period of monitoring the thermo-hygrometric values, with control units that have returned useful values of the temperature and humidity trends in the environment in relation to seasonal cycles.


The scientific approach pursued, for the Cathedral, led to the application of simulation models in three dimensions using computational fluid dynamics codes (thermo-fluid dynamics analysis), for the verification of convective motions hypothesized in some exceptional points, such as the vestibule and the Malinti chapel, which houses the table of the Annunciation by Titian italian painter.


According to a simplified approach to the problem, which used part of the aforementioned analyzes, the audit phase consisted of taking note of the existing situation:

• absence of a heating system;

• high ambient humidity values;

• obsolescence of existing electrical and lighting systems;

• absence of a video control / anti-intrusion system.


The presence of high humidity, with evident repercussions both on environmental well-being, such as to prevent the celebratory use of the Baptistery in the winter months, and on the state of conservation of the building, determined by the absence of a heating system, together with the quality deficit building technology, constitute the synthesis of the audit phase.





If for the summer period the problem of the indoor climate is generally less relevant, given that the high thermal inertia of the walls and the reduced size of the windows compared to the total volume of the building guarantee good levels of comfort and avoid the phenomenon of overheating, during the cold season the problem of heating becomes more emerging, both for the well-being of the faithful gathered in the hall, and for the conservation of the building and the sacred and cult objects, relics, works of art, organs, decorations .


The existing lighting system in the Baptistery was technologically obsolete and essentially indifferent to the artistic and architectural values of the place. The altar and the hall were illuminated by halogen projectors of different sizes, with large energy losses due to the Joule effect. The two small apses on either side of the presbytery featured a system of recessed projectors arranged on an improvised plywood top. Neon tubes were housed on the extrados of the wooden tie-rod of three of the seven roof trusses.



On the construction site, during the excavation phase carried out according to the prescription of archaeological assistance, some wall sections emerged: in-depth archaeological investigations followed, carried out under the direction of the Archaeological Superintendence of Veneto, which brought to light a burial and the ancient baptismal font.


These are significant interferences with the authorized executive project, which required the adaptation of the floor stratigraphy (heating integrated service package and flooring) and design solutions suitable for inspection for subsequent studies of the findings ancient and original structures.




Restoration or rehabilitation works


The retrofit project of the monumental complex of the Treviso Cathedral and complementary works results as a whole of the reunification in a single and interconnected system of the monumental buildings owned by the Diocese and the Chapter of the Treviso Cathedral, open to the local community and to cultural tourism of quality; this assumption has led to a series of interventions considered a priority by the client, preparatory and functional to maintaining the integrity, functional efficiency and identity of the ecclesiastical cultural asset and all its parts.



The design of the heating system involved a multiplicity of disciplinary skills, requiring to reconcile needs of different nature, such as: liturgy and use of the church, taste of the people involved, local traditions, costs, energy saving, thermal comfort of the congregation, impact visual, environmental impact, invasive impact of the system (damage structures), compatibility with the conservation of cultural heritage.


During the drafting of the preliminary project, a comparative analysis of the heating methods that can be adopted was carried out, given the multiplicity of needs expressed by the Client, which see the coincidence of liturgical uses and exhibition uses: the church in fact, due to the role it plays for the city (it is the Baptistery of the cathedral church) sees as its main function the religious one (liturgical celebrations), and as a complementary (but no less important) function the opening to compatible cultural tourism (exhibitions and exhibitions), which suits the city of Treviso.




The heating system designed is underfloor radiant type. This choice was made for:

– allow the use of continuous heating in winter, congruent with liturgical needs;

– encourage the use of the ecclesial hall while respecting the original construction tradition;

– keep operating costs low;

– determine an energy saving condition;

– ensure high thermal comfort for the assembled assembly;

– cancel any visual impact of the system;

– minimize the environmental impact of the plant system;

– admit compatibility with the building’s original characteristics, improving the microclimatic conditions.


The new system, extended to the entire Baptistery and adjacent sacristy, consists of:

– thermal power plant with production of hot water by means of a high-efficiency condensing methane gas boiler, climatic regulation and accessory equipment of the thermal power heating service;

– radiant panels inserted in concrete, after the interposition of a separation layer in geotextile and an insulating layer of polystyrene;

– pipes in thermoplastic material equipped with an oxygen barrier laid on an electro-welded mesh;

– distribution manifolds;

– electrical system complete with connection for pumping and automation for electrical and electronic regulation.


The heating control, limited to the supply temperature of the panels according to climatic and environmental needs, provides guarantees of maintaining comfort inside the baptistery throughout the winter period.



The heating system is completely hidden under the new clay-colored floor with a thickness of about 3 cm.


The flooring therefore consists of a continuous screed made on site that defines a monolithic layer composed of a mixture of cocciopesto (selected, bio-ecological product), aggregates and natural hydraulic lime-based binder, on which the subsequent smoothing natural materials, consisting of a mixture of quartz aggregates, pozzolanic binders, natural white lime (NHL), kaolin and additives.


A corten steel profile defines the technical joint of the flooring with the perimeter walls, conceals the cavity where the electrical wiring is completely concealed; this profile is also useful to allow the thermal expansion of the different layers without causing fractures.




Among the salient aspects of the lighting project, which involves the adoption of LED-type sources, the articulation of lighting scenarios, to define different configurations congruent to the various phases of the liturgy (Initial Rites, Liturgy of the Word, Eucharistic Liturgy, Conclusion), and especially the rite of baptism: these scenarios allow for the quantity (and quality) of the light provided, individual and community prayer, tourist visits, special events (exhibitions, concerts, performances or particular ceremonies), as well as to service and safety lighting.


The choice of LED light sources meets the following performance requirements:

• luminous efficiency, for obvious economic reasons;

• the high color rendering;

• the luminance;

• lifespan and maintenance of the luminous flux over time;

the color temperature suitable for the materials and characteristics of the surfaces to be illuminated;

• the possibility of a quick start up and an equally quick restart after a short power failure, in cases where different ignition regimes have to occur.



The choice of lighting bodies complies with the following performances:

• excellent light output;

• photometric characteristics suitable for the visual task;

• the provision of easily accessible devices to block direction aiming, in cases where the maintenance of such direction is essential for the success of the work;

• the degree of protection (IP) in relation to the installation position and the orientation of the device;

• the overall dimensions in harmony with the place;

• safety and stability in the installation.


The lighting system, minimized in physical dimensions and visual perception, provides for the masking of the cable-carrying channels and the arrangement of the back lines in the extrados of the truss chains.


Particular attention was paid to forecasting the management and maintenance of the system: the designed home automation system consists of a control panel, distinct from the energy one, in which each light scenario can be activated by pressing a simple button (touch screen).


Accessibility (Design for all)

The intervention project is also aimed at implementing accessibility, through the introduction of a stairlift connected to the staircase built in the thirties of the twentieth century; this design solution involved adjusting the elevation of the stair arrival floor, to bring it back to the same access level as the baptistery.




Assessment of the results


The intervention at the Treviso Baptistery intends to propose the outcome of a research (a path intellectual and technical), with the aim of reconnecting architecture (and the figure of the architect) to the (also) technological and plant engineering choices of the project.


In a historical phase characterized by a very high level of attention to the energy and environmental aspects of the built environment, the retrofit action declined in the particularity of an ecclesiastical cultural asset, constitutes an extremely relevant cultural node before being a technical one, emergency of the Italian reality.


If on the one hand the European regulatory framework directs interventions towards nZEB buildings, it appears almost impossible to apply to cultural heritage and in particular to religious buildings, processes characterized by incident actions, the performance improvement of the envelope and the realization of plant systems for the ‘self-production of energy (solar, wind, geothermal, etc.).


The intervention on the Treviso Baptistery is part of an overall and articulated project for the enhancement of the Complex of the Cathedral of S. Pietro Apostolo in Treviso.

It highlights an obsolete procedure for the enhancement of an ecclesiastical cultural asset, which starts from plant-type interventions (mainly: heating and lighting) to which an architectural value has also been attributed.



References / sources and literature


Recupero e conservazione Magazine nn.142 (July-August 2017) and 143 (September-October 2017)