An effective strategy for preventive conservation in historic buildings coupling dynamic simulation and experimental data of indoor climate

La conservazione preventiva consiste in tutte quelle attività che consentono di mitigare il degrado dei Beni Culturali. Tra queste attività, lo studio delle condizioni ambientali è fondamentale per valutare il processo di degrado così come per gestire e tutelare il patrimonio culturale. L’invecchiamento di un oggetto e l’alterazione delle sue proprietà chimico-fisiche e strutturali sono processi innescati e regolati in modo diretto e indiretto dal microclima e dalle sue fluttuazioni. Qualsiasi allontanamento dalle condizioni ambientali, in particolar modo dall’umidità relativa (UR), che ha favorito la conservazione del manufatto fino a oggi (clima storico), potrebbe essere deleterio alla sua futura tutela. Per questo motivo, l’interesse dei conservatori scientifici è rivolto a trovare metodologie di studio che consentano di rallentare, prevedere e prevenire il degrado. La combinazione di misure sperimentali e simulazione dinamica del clima interno risulta efficace (a) a diagnosticare le cause che determinano il microclima e (B) a prevedere il suo comportamento in caso di modifiche delle condizioni a contorno. Tuttavia, l’efficacia della simulazione dinamica degli edifici dipende fortemente dall’accuratezza del modello di edificio, che dovrebbe esser in grado di derivare le fluttuazioni a medio e lungo termine, in particolar modo quelle di UR, che è complessa da simulare a causa della sua dipendenza da molti fattori. Di conseguenza, l’uso della simulazione dinamica può essere efficace solo quando l’umidità relativa è misurata, analizzata e modellata accuratamente. Questa tesi affronta un argomento molto importante nel campo della conservazione preventiva, fornendo una strategia per il controllo e la gestione del microclima all’interno di edifici storici che ospitano collezioni permanenti. Per raggiungere questo obiettivo, la ricerca si è focalizzata sull’uso combinato di studi sperimentali e di simulazione dinamica. Particolare attenzione è stata indirizzata alla modellazione dell’umidità così come ai fenomeni di degrado meccanico indotti dall’umidità nei materiali igroscopici. Esistevano quattro ragioni per condurre questa ricercar: (1) fornire una valutazione oggettiva circa la qualità delle misure microclimatiche; (2) sviluppare una funzione di danno specifica per il degrado meccanico; (3) estendere le caratteristiche di una software commerciale di simulazione dinamica degli edifici con un modello monodimensionale di trasferimento simultaneo di calore e vapore attraverso le pareti; (4) facilitare il settaggio dei parametri necessari alla costruzione del modello di edificio a partire dai dati orari di temperatura e umidità relativa. I punti (3) e (4) erano necessaria per usare la simulazione dinamica come uno strumento diagnostico. Il punto (2) era necessario per estendere l’uso della simulazione anche a strumento prognostico. La metodologia proposta da questa ricerca consiste di tre fasi: (i) monitoraggio microclimatico e sua caratterizzazione per la valutazione del rischio di degrado basata un modello dose-risposta; (ii) creazione del modello di edificio e sua taratura; (iii) uso dei modelli tarati di edificio e di degrado per prevedere l’evoluzione del microclima dopo una nuova strategia di controllo microclimatico. Gli obiettivi specifici precedentemente elencati sono stati raggiunti usando differenti casi studio, mentre l’intera metodologia è stata applicata con successo al Museo Archeologico di Priverno che potrebbe essere definito come caso studio pilota. La combinazione di misure microclimatiche insieme alla simulazione dinamica si è dimostrata uno strumento potente and flessibile per la valutazione di una soluzione di controllo microclimatico in edifici storici. L’approccio proposto risulta essere completamente non invasivo, non distruttivo e con costo-zero in termini di materiali (se si esclude il costo del monitoraggio microclimatico). Infatti, le qualità conservative degli spazi da esposizione dopo la modifica del microclima sono direttamente valutate nell’ambiente di simulazione. In questo modo, i risultati possono sostenere vantaggiosamente i processi decisionali riguardanti il controllo e la gestione dell’ambiente espositivo.The preventive conservation consists in all activities that allow to mitigate the degradation of cultural heritage. Among these activities, the study of environmental conditions is crucial to assess the degradation process as well as to manage and preserve the cultural heritage. The ageing of an object and the alteration of chemical-physical properties are activated and controlled, directly and indirectly, by the microclimate and its fluctuations. Any departure from the microclimate, especially the relative humidity (RH), that has promoted the conservation of an object (historical climate) might be harmful to its future preservation. For this reason, conservation scientists focus on methodologies able to reduce, predict and prevent the degradation. Combining experimental and modelling approaches in studies of indoor climate proves to be effective (a) to diagnose key factors that determine the microclimate and (b) to predict its dynamic behaviour if boundary conditions change. However, the efficacy of the building dynamic simulation strongly depends on the accuracy of the building model, that should derive both short- and long-term fluctuations of the indoor climate variables, especially those concerning RH, which is, besides, complex to simulate due to its dependence on many factors. Consequently, the use of dynamic simulation can be effective only when the relative humidity is accurately measured, analysed and modelled. This thesis addresses a very important timely topic in the preventive conservation providing a strategy in the control and management of the indoor climate within historic buildings which house permanent collections. To achieve this purpose, the research focused on combining experimental and dynamic simulation studies. Particular attention was paid to moisture modelling as well as to the moisture-induced damage in hygroscopic materials. There were four main reasons to have prompted this research: (1) providing an objective assessment about the quality of indoor climate measurements; (2) developing a damage function specific for mechanical degradation; (3) extending the features of a commercial building dynamic simulation software with a one-dimensional heat and moisture transfer model; (4) easing the set-up of the building model using hourly climate variables instead of energy data. The issues (3) and (4) were needed for using the dynamic simulation as a diagnostic tool. The issue (2) was needed for extending the use of simulation from a diagnostic tool to a predictive tool. The methodology proposed by this research consists of three steps: (i) microclimate monitoring and its characterization for conservation risk assessment based on dose-response model; (ii) creation of a building model and its calibration; (iii) use of calibrated building and dose-response models to predict the microclimate evolution after a new strategy of microclimate control. The specific purposes were achieved using different case studies and the whole strategy (i.e. the general purpose) was successfully exploited in the case of “Archaeological Museum of Priverno”, which might be defined as the pilot case study. The combination of indoor climate measurements jointly with the dynamic simulation has demonstrated to be a powerful tool to assess a climate control solution within historic buildings. The proposed approach results to be completely non-invasive, non-destructive and with zero-costs in terms materials. Indeed, the conservative quality of the exhibition spaces after modification of the indoor climate is directly assessed in the simulation environment. In this way, outcomes can support advantageously decision-making for a better control and management of the exhibition environment

Discontinuities and hysteresis in quantized average consensus

We consider continuous-time average consensus dynamics in which the agents' states are communicated through uniform quantizers. Solutions to the resulting system are defined in the Krasowskii sense and are proven to converge to conditions of "practical consensus". To cope with undesired chattering phenomena we introduce a hysteretic quantizer, and we study the convergence properties of the resulting dynamics by a hybrid system approach.Comment: 26 pages, 7 figures. Accepted for publication in Automatica. v4 is minor revision of v

Illuminazione nell’architettura antica: ipotesi ricostruttive delle modalità di comunicazione visuale in alcuni contesti di edilizia religiosa tra V e VI secolo d.C.

Tema di questa ricerca è lo studio delle modalità di illuminazione artificiale e naturale dello spazio sacro in alcuni contesti di architettura religiosa di V e VI secolo. I contesti architettonici prescelti per questo studio sono la Basilica dell'Acheiropoietos di Salonicco e la Basilica dei Santi Sergio e Bacco, di Costantinopoli, dei quali sono stati realizzati dei modelli tridimensionali con il supporto della grafica computerizzata. Oltre allo studio dei due edifici e delle loro fasi edilizie (nonché delle loro compagini architettoniche e degli apparati di arredo liturgico), si è inteso cercare di ricostruire gli schemi di illuminazione artificiale al loro interno. A tal fine è stato condotto un lavoro preliminare di studio ad ampio raggio su questa classe di manufatti provenienti da scavi di edifici di culto di età tardo antica e protobizantina, con una particolare attenzione a quei siti che hanno restituito informazioni puntuali sul posizionamento dei lumi. Oltre a ciò sono stati considerati anche manufatti fuori contesto, contenuti in collezioni museali o private, nonchè le rappresentazioni iconografiche di questi oggetti nelle fonti documentali (anche più tarde). Un particolare approfondimento è stato dedicato alle fonti scritte che trattano, anche in maniera incidentale, di questi manufatti, soprattutto in relazione ad uno dei due casi scelti, ossia la Basilica dei Santi Sergio e Bacco. Sono stati quindi proposti schemi di distribuzione dei lumi fissi e, in parte, anche mobili per ricostruire l'assetto luminoso delle basiliche durante le celebrazioni liturgiche diurne festive. La seconda parte dello studio, invece, è consistita nel realizzare delle simulazioni virtuali, ottenute con l'ausilio della computer grafica, dell'illuminazione naturale di questi edifici in antico. Grazie ad un particolare applicativo, infatti, è stato possibile impostare la fonte luminosa naturale (sun) nel mondo virtuale calcolandone la posizione in un dato momento/giorno/anno georiferendo i modelli tridimensionali

A method for an effective microclimate management in historical buildings combining monitoring and dynamic simulation: the case of “Museo Archeologico di Priverno”

In this work a method is proposed to estimate the effect of indoor microclimate on the risk of degradation of ancient materials stored in historical buildings. The method, which combines microclimate observations and dynamic simulation, has shown to be strategic in preventive conservation of historical buildings. Indeed, once the building model is calibrated, it can be effectively used for evaluating the microclimate control solutions on the conservation reducing general degradation risks. The method has been applied to a historical building close to Rome, where deteriorations in ceilings occurred and visitors complain about thermal discomfort. First, the HVAC system in the model has set in order to guarantee both thermal comfort and adequate condition for the conservation of the material. Then, the crack width of wooden ceiling has been estimated by means of an empirical model based on indoor temperature and relative humidity data and validated with the measurements of the crack width. It was found a reduction of annual variation from 0.4 mm to 0.2 mm, experimented by panels, and an improvement of maximum daily variation, especially in winter and summer (less than 0.01 mm on average)

Modeling limited attention in opinion dynamics by topological interactions

This work explores models of opinion dynamics with opinion-dependent connectivity. Our starting point is that individuals have limited capabilities to engage in interactions with their peers. Motivated by this observation, we propose a continuous-time opinion dynamics model such that interactions take place with a limited number of peers: we refer to these interactions as topological, as opposed to metric interactions that are postulated in classical bounded-confidence models. We observe that topological interactions produce equilibria that are very robust to perturbations.Comment: To be presented at NETGCOOP 2020; revised version including simulation

Modeling limited attention in opinion dynamics by topological interactions

This work explores models of opinion dynamics with opinion-dependent connectivity. Our starting point is that individuals have lim-ited capabilities to engage in interactions with their peers. Motivated bythis observation, we propose a continuous-time opinion dynamics modelsuch that interactions take place with a limited number of peers: we re-fer to these interactions astopological, as opposed tometricinteractionsthat are postulated in classical bounded-confidence models. We observethat topological interactions produce equilibria that arevery robust todisruption

Performance assessment of hygrothermal modelling for diagnostics and conservation in an Italian historical church

The hygrothermal modelling of historical churches is a promising approach to study preservation issues and suitable retrofit measures. However, difficulties can arise in the use of Heat, Air and Moisture (HAM) models, which are often customised objects to be integrated into validated building energy simulation (BES). This research outlines a multi-step methodology to investigate the capability of a BES software coupled with a HAM model (BES + HAM) as a technique for diagnostics and conservation in complex settings. The 17th-century church of Santa Rosalia (Italy) was used as a historical site in a real context. As first step, the performance of the simulation tool was analysed through standardised exercises aiming at excluding incorrect assumptions and calculations in the HAM model (HMWall). Secondly, a building model of the church using a 1D heat transfer model (named building model A) was compared with one using HMWall (named building model B) in terms of the accuracy of the indoor climate simulations against hygrothermal measurements. The results showed that building model B enhanced the simulation accuracy by +50% with respect to building model A. Finally, annual simulations inside the church were run to further compare the seasonal trends of indoor climate scenario obtained from the two building models. Building model B allowed to study the water content distribution inside the altarpiece and a wall partition, showing that BES + HAM tools can be used to identify potential moisture-induced conservation risks

Optimising conservation of artworks, energy performance and thermal comfort combining hygrothermal dynamic simulation and on-site measurements in historic buildings

The indoor climate conditions being suitable for the conservation of cultural heritage can be conflicting with energy saving and thermal comfort. Moreover, the moisture dynamics have not been studied enough in the simulation of the indoor environment, even though its interaction with artworks is crucial in deterioration phenomena. This research aims at defining a strategy, based on experimental data and dynamic simulation of hygrothermal behaviour, in order to design a HVAC system able to simultaneously satisfy conservation, thermal comfort and energy requirements. A weighted function for the multi-objective optimization has been proposed and effectively used to pinpoint the combination of temperature and relative humidity set-points

Examination on total ozone column retrievals by Brewer spectrophotometry using different processing software

The availability of long-term records of the total ozone content (TOC) represents a valuable source of information for studies on the assessment of short-and long-term atmospheric changes and their impact on the terrestrial ecosystem. In particular, ground-based observations represent a valuable tool for validating satellite-derived products. To our knowledge, details about software packages for processing Brewer spectrophotometer measurements and for retrieving the TOC are seldom specified in studies using such datasets. The sources of the differences among retrieved TOCs from the Brewer instruments located at the Italian stations of Rome and Aosta, using three freely available codes (Brewer Processing Software, BPS; O3Brewer software; and European Brewer Network (EUBREWNET) level 1.5 products) are investigated here. Ground-based TOCs are also compared with Ozone Monitoring Instrument (OMI) TOC retrievals used as an independent dataset since no other instruments near the Brewer sites are available. The overall agreement of the BPS and O3Brewer TOC data with EUBREWNET data is within the estimated total uncertainty in the retrieval of total ozone from a Brewer spectrophotometer (1%). However, differences can be found depending on the software in use. Such differences become larger when the instrumental sensitivity exhibits a fast and dramatic drift which can affect the ozone retrievals significantly. Moreover, if daily mean values are directly generated by the software, differences can be observed due to the configuration set by the users to process single ozone measurement and the rejection rules applied to data to calculate the daily value. This work aims to provide useful information both for scientists engaged in ozone measurements with Brewer spectrophotometers and for stakeholders of the Brewer data products available on Web-based platforms

Investigation on the Use of Passive Microclimate Frames in View of the Climate Change Scenario

[EN] Passive microclimate frames are exhibition enclosures able to modify their internal climate in order to comply with paintings¿ conservation needs. Due to a growing concern about the effects of climate change, future policies in conservation must move towards affordable and sustainable preservation strategies. This study investigated the hygrothermal conditions monitored within a microclimate frame hosting a portrait on cardboard with the aim of discussing its use in view of the climate expected indoors in the period 2041¿2070. Its effectiveness in terms of the ASHRAE classification and of the Lifetime Multiplier for chemical deterioration of paper was assessed comparing temperature and relative humidity values simultaneously measured inside the microclimate frame and in its surrounding environment, first in the Pio V Museum and later in a residential building, both located in the area of Valencia (Spain). Moreover, heat and moisture transfer functions were used to derive projections over the future indoor hygrothermal conditions in response to the ENSEMBLES-A1B outdoor scenario. The adoption of microclimate frames proved to be an effective preventive conservation action in current and future conditions but it may not be sufficient to fully avoid the chemical degradation risk without an additional control over temperatureThis project received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No. 814624. This research was partially supported by the Plan Nacionalde I+D, Comision Interministerial de Ciencia y Tecnologia (FEDER-CICYT) under project HAR2013-47895-C2-1-P.Verticchio, E.; Frasca, F.; García Diego, FJ.; Siani, AM. (2019). Investigation on the Use of Passive Microclimate Frames in View of the Climate Change Scenario. Climate. 7(8):1-14. https://doi.org/10.3390/cli70800981147