Assessing energy performance and indoor comfort in places of worship

Assessing Energy Performance and Indoor Comfort in Places of Worship Robert C. Vella Director: Prof. Ing. Charles Yousif Co-Director: Prof. Francisco Javier Rey Martinez Doctor of Philosophy (PhD) Degree in Industrial Engineering Escuela de Ingenierías Industriales Departamento de Ingeniería Energética y Fluidomecánica Universidad de Valladolid, Spain September 2022 I PREFACE This doctoral dissertation is presented as a compendium of publications published in three scientific articles and one complimentary conference paper, in conformity to the ANECA criteria and in joint contribution, describing the overall objectives pursued, the methodology employed, and the results achieved within each respective research component. II LIST OF PAPERS Complementary Paper Complementary Paper entitled ‘Monitoring Indoor Temperatures of Places of Worship: A First Step Towards Energy Sustainability Engineering Sustainability and Sustainable Energy’; (ESSE’18) Conference organised by the Chamber of Engineers in collaboration with the Institute for Sustainable Energy of the University of Malta, ISBN: 978-99957-853-2-1 [1] Statistics (August 2022) Open Access Repository University of Malta https://www.um.edu.mt/library/oar/handle/123456789/30540/statistics Citations: 1 No. of Views: 104 views File Downloads: 145 downloads III Paper 1 Scientific Article No.1 entitled ‘A study of thermal comfort in naturally ventilated churches in a Mediterranean climate’; published by Energy & Buildings Journal, Volume 213, 2020, 109843, ISSN 0378-7788, https://doi.org/10.1016/j.enbuild.2020.109843 [2]. Citations (August 2022) Google Scholar 17 Scopus 15 Clarivate Web of Science 12 Abstract views: 80 Full text downloads: 39 ResearchGate Reads: 105 Rank by Journal Impact Factor: 7.201 (2021) Energy & Buildings JCR Category Q1 Rank in Category: Engineering Buildings and Construction 09/211 SCImago Journal Rank (SJR): 1.682 (2021) IV Paper 2 Scientific Article No.2 entitled ‘Thermal Comfort in Places of Worship within a Mediterranean Climate’; published by Sustainability Journal 2021, 13, 7233, https://doi.org/10.3390/su13137233 [3]. Citations (August 2022) Google Scholar 1 Scopus 1 Clarivate Web of Science 1 Abstract views: 797 Full text downloads: 737 ResearchGate Reads: 62 Rank by Journal Impact Factor: 4.17 (2021) JCR Category Q2 Rank in Category: Sustainability 50/211 SCImago Journal Rank (SJR): 0.664 (2021) V Paper 3 Scientific Article No.3 entitled ‘Prioritising Passive Measures over Air Conditioning to Achieve Thermal Comfort in Mediterranean Baroque Churches’; published by Sustainability Journal 2022, 14, 8261, https://doi.org/10.3390/su14148261 [4]. Citations (August 2022) Google Scholar 0 Scopus 0 Clarivate Web of Science 0 Abstract views: 293 Full text downloads: 206 ResearchGate reads: 24 Rank by Journal Impact Factor: 4.17 (2021) JCR Category Q2 Rank in Category: Sustainability 50/211 SCImago Journal Rank (SJR): 0.664 (2021) VI ABSTRACT Buildings are responsible for more than 40% of the total energy consumption and greenhouse gas emissions in Europe. As a result, the EU has enacted several rules aimed at increasing energy efficiency and limiting the growth of energy demand. However, it is pertinent to point out that places of worship are exempt from getting an energy rating certificate under the European Union Energy Performance in Buildings Directive 2010/31/EU. Malta is completely reliant on imported energy supplies due to a lack of fossil fuel resources. This, to the cost of national security, price volatility, political and environmental concerns, amongst other things. Controlling and managing energy use in buildings is one efficient strategy to reduce this reliance. Excessive energy flow through the building envelope and, unregulated use of air-conditioning are some common drivers of energy waste in buildings. This thesis aims to assess the energy performance of places of worship and combine it with indoor comfort analysis. Passive measures to improve internal comfort levels are identified and prioritised to address heat transfer through the building envelope and mitigate the emerging trend of installing air-conditioning systems. This study takes into consideration the status quo of various places of worship of different building eras using a monitoring programme for temperature and humidity within these buildings. It further delves into the social aspect of how worshipers perceive the indoor comfort through questionnaires addressed to the occupants. Subsequently, it analyses how passive measures can improve the indoor ambient conditions through software design modelling using DesignBuilder-Energy Plus software. This analysis show that historic church structures outperform expectations. The heritage building typology provides promising possibilities for lowering energy consumption, maintaining balanced environmental conditions for artifacts, and meeting occupant comfort standards. The findings pertaining to the monitoring program demonstrate that the church buildings under study, representing the 17th to mid-18th century Baroque period, are termed as thermally comfortable in accordance with the EN16798-1 standard category 3 comfort limits. Moreover, results exhibit the capacity of their heritage construction typology, to maintain balanced environmental conditions when compared to the fluctuated indoor VII temperatures in the contemporary churches. The latter, pertaining to the more contemporary construction methodologies of the churches, jeopardises their thermal comfort, having recorded temperatures exceeding the broadest comfort range limits. Findings through statistical analysis of both quantitative research based on indoor measurable data and qualitative research based on replies to questionnaires from churchgoers, also show that there is a significant correlation between the actual thermal comfort levels measured in accordance with the EN 16798-1 standard and the expected thermal comfort experienced by congregants in most of the parish churches under review. The implementation of passive measures within selected churches, particularly the implementation of solar control strategies that improves the building envelope's thermal performance, significantly decreased heat discomfort. The outcome highlights differences between diverse types of church buildings, depending on their era, site constraints and methodology of construction, together with a list of passive and non-intrusive recommendations for enhancing the comfort of worshipers and improving the energy efficiency aspects of these buildings, whilst respecting their architectural heritage and artefacts with which they are adorned. VIII RESUMEN Los edificios en la EU representan más del 40 % del consumo total de energía y el 36% de las emisiones de gases de efecto invernadero, GEI. Como consecuencia de esto, la EU establece un marco político en materia tanto de energía como de cambio climático promulgado varias directivas y programas de acción como el Green Deal, destinadas a aumentar la eficiencia energética, y reducción de los gases GEI. Es pertinente señalar que los lugares de culto están exentos de obtener un certificado de calificación energética en virtud de la Directiva de Eficiencia Energética en Edificios de la Unión Europea 2010/31/UE. Malta depende completamente de los suministros de energía importados debido a la falta de recursos propios de combustibles fósiles, al costo de la seguridad nacional, la volatilidad de los precios, las preocupaciones políticas y ambientales, entre otras cosas. Una forma eficaz de reducir esta dependencia es gestionar y controlar el consumo energético de los edificios. El flujo excesivo de energía a través de la envolvente del edificio, el uso no regulado del aire acondicionado y la falta de ventilación son causas comunes de la ineficiencia de energía en los edificios. Estos factores no pueden resolverse fácilmente y, a su vez, es necesario realizar una cantidad considerable de investigación para identificar las principales debilidades de cada uno de ellos. Esta tesis tiene como objetivo el análisis e identificación de las medidas tecnológicas pasivas que se pueden adoptar en los lugares de culto, para abordar la transferencia de calor a través de la envolvente del edificio y la tendencia emergente de instalar sistemas de aire acondicionado. Este estudio tiene en cuenta el status quo de varios lugares de culto de diferentes épocas de construcción, profundiza en el aspecto social de cómo los fieles perciben el confort interior y analiza cómo las medidas tecnológicas pasivas pueden mejorar las condiciones ambientales. Para llevar a cabo la metodología de este estudio se establece un programa de monitorización de temperatura seca y humedad relativa dentro de los edificios, de culto, así como cuestionarios de elaboración propia, dirigidos a los miembros de la comunidad y su análisis estadístico. Otra herramienta teórica empleada, es una simulación dinámica de energía, mediante el software reconocido internacionalmente DesignBuilder que XV LIST OF FIGURES Figure 1: The Parish Church of St. Mary in Birkirkara. The dome and roof were destroyed in an earthquake on 24 June 1856. ............................................................................................................... 11 Figure 2: The Matrix Parish church of the Nativity of Mary in Naxxar. Photograph by author RCV (2022). ................................................................................................................................................... 11 Figure 3: Part Plan and Elevation of The Parish Church and Sanctuary of Our Lady of Graces in Zabbar. .................................................................................................................................................. 12 Figure 4: The Parish Church and Sanctuary of Our Lady of Graces in Zabbar. Left: The ceremony of the raising of the cross on top of the dome in 1928. Right: Photograph by author RCV (2022). ......... 13 Figure 5: Basilica of the National Shrine of the Blessed Virgin of Ta' Pinu, Għarb, Gozo. An architectural masterpiece built between 1920 and 1931 with superb sculptures and craftsmanship in Maltese Limestone. Photograph by author RCV (2022). ...................................................................... 13 Figure 6: The Parish Church of the Annunciation of Our Lady, Birgu (Vittoriosa). Photographs by author RCV (2016). ................................................................................................................................ 22 Figure 7: Remarkable works of art and artefacts in churches. Photographs by author RCV (2022). ... 24 Figure 8: Detail of part of the falling painting depicting the Plan of Salvation by Chevalier Emvin Cremona in 1977. Courtesy of the Balzan Heritage Commission 2006. ............................................... 25 Figure 9: Church of Our Lady of Jesus (Ta’ Giezu), Rabat, Malta. 16th Century Church Ceiling Collapse on 23 August 2017. Pictures courtesy of the Franciscan Fathers. ........................................................ 26 Figure 10: Plan of the ‘Chiesa Conventuale di San Giovanni Battista’, Valletta. ................................. 27 Figure 11: St John's Co-Cathedral, Valletta. Photographs by author RCV (2022). ................................ 28 Figure 12: St John's Co-Cathedral, Valletta. Photographs by author RCV (2022). ................................ 29 Figure 13: The St John’s Co-Cathedral Museum Project, Valletta. Courtesy of the St John’s CoCathedral Foundation. .......................................................................................................................... 30 Figure 14: The Oratory Restoration Project. St John's Co-Cathedral, Valletta. Photographs by author RCV (2021). ........................................................................................................................................... 32 Figure 15: The St. John's Co-Cathedral Museum Project, Valletta. Photographs by author RCV (2022). .............................................................................................................................................................. 34 Figure 16: Luqa Reservoir; known as the ‘sunken cathedral’, constructed at around 1907. Courtesy of the Malta Water Services Corporation. ................................................................................................ 35 Figure 17: Our Lady of the Annunciation Balzan Parish Church. Photographs by author RCV (2018). 39 Figure 18: Our Lady Star of the Sea, Stella Maris Parish Church, Sliema. Photographs by author RCV (2018) .................................................................................................................................................... 41 Figure 19: St. Joseph Parish Church, Msida. Photographs by author RCV (2018-2020) ....................... 43 Figure 20: Santa Venera Parish Church, Santa Venera. Photographs by author RCV (2018-21). ......... 45 Figure 21: Our Lady of Mount Carmel Parish Church, Fgura. Photographs by author RCV (2018-21). 47 Figure 22: Geological map of the Maltese Islands. ............................................................................... 48 Figure 23: Plan of the Parish Church of Our Lady of Loreto in the village of Għajnsielem, Gozo. ....... 49 Figure 24: Ghajnsielem Parish Church (Gozo, Malta). Photographs by author RCV (2022) ......... 50 Figure 25: St. Francis of Assisi Qawra Parish Church, San Pawl il-Bahar. Photograph by author RCV (2021). ................................................................................................................................................... 52 Figure 26: The Convent & Sanctuary Church of St. Therese of Lisieux, Birkirkara. .............................. 52 XVI Figure 27 - Design values for the indoor operative temperature for buildings without mechanical cooling systems as a function of the exponentially weighted running mean of the outdoor temperature. ......................................................................................................................................... 56 Figure 28 - Comparative Analysis of Nave Temperature (T °C) Fluctuations of the five churches under study...................................................................................................................................................... 61 Figure 29 - Comparative Analysis of Nave Humidity (RH %) Fluctuations of the five churches under study...................................................................................................................................................... 61 Figure 30 - Balzan – The Annunciation Parish Church – EN 16798-1 Category 3 Comfort Analysis ..... 66 Figure 31: Stella Maris Parish Church – EN 16798-1 Category 3 Comfort Analysis. ............................. 67 Figure 32 - Msida – St. Joseph Parish Church – EN 16798-1 Category 3 Comfort Analysis .................. 68 Figure 33 - Santa Venera – Santa Venera Parish Church – EN 16798-1 Category 3 Comfort Analysis . 69 Figure 34 - Fgura – Our Lady of Mount Carmel Parish Church – EN 16798-1 Category 3 Comfort Analysis. ................................................................................................................................................ 70 Figure 35: Bar graph representing different comfort levels in the different parish churches in summer and winter. ............................................................................................................................................ 74 Figure 36 - Bar graph representing the difference in comfort levels between males and females in the different parish churches in summer and winter. .......................................................................... 75 Figure 37 - Column graph representing the difference in comfort levels between the four different age groups in the different parish churches in both summer and winter. ........................................... 76 Figure 38 - Sliema Simulated Indoor Temperature including 3mm White Acrylic Polymer Paint (Occupied Hours). ................................................................................................................................. 80 Figure 39: Fgura Simulated Indoor Temperature including 3mm White Acrylic Polymer Paint (Occupied Hours). ................................................................................................................................. 81 Figure 40 - Sliema Simulated Indoor Temperature including 5cm/10cm EPS Extruded Polystyrene (Occupied Hours) .................................................................................................................................. 82 Figure 41 - Fgura Simulated Indoor Temperature including 5cm/10cm EPS Extruded Polystyrene (Occupied Hours) .................................................................................................................................. 83 XVII LIST OF TABLES Table 1: Physical characteristics of the church buildings under study. ................................................ 37 Table 2: Location of Sensors - Vertical height ....................................................................................... 53 Table 3: Specifications of Data Logger .................................................................................................. 54 Table 4: Description of the applicability of the categories used (EN 15251) ........................................ 57 Table 5: Questionnaire survey (English version) ................................................................................... 72 XVIII LIST OF ABBREVIATIONS • ACs Air Conditioners • BLE Bluetooth Low Energy • BMJ British Medical Journal • CO2 Carbon Dioxide • COVID Coronavirus Disease • CTS Current Thermal State • EEMs Energy Efficiency Measures • EPBD European Union Energy Performance in Buildings Directive 2010/31/EU • EPS Extruded Polystyrene Standard • ESSE Engineering Sustainability and Sustainable Energy • EU European Union • EUCA Energy Union and Climate Action • FFL Finished Floor Level • GHSR Global Heritage Stone Resource • H Humidity • HSS Heritage Stones Sub-commission • HVAC Heating, Ventilation, and Air Conditioning • IEA International Energy Agency • IEQ Indoor Environmental Quality • IMQ Indoor Microclimatic Quality • IUGS International Union of Geological Sciences • MIA Malta International Airport • MOD Meteorological Office Data • NECP National Energy and Climate Plan • NICPMI National Inventory of the Cultural Property of the Maltese Islands • NOAA The National Oceanic and Atmospheric Administration • NREAP National Renewable Energy Action Plan • PM Passive Measures • PMV Predicted Mean Vote • PPD Predicted Percentage of Dissatisfied • RBs Reference Buildings • RH Relative Humidity • SCH Superintendence of Cultural Heritage • SPSS Statistical Package for the Social Sciences • T Temperature • TSS Thermal Sensation Survey • UNEP United Nations Environment Program • UNESCO United Nations Educational, Scientific and Cultural Organisation • ZEBs Zero Energy Buildings 1 SETTING THE SCENE According to the National Oceanic and Atmospheric Administration's (NOAA) annual report for 2022, the nine years from 2013 to 2021 were all among the ten warmest on record [5], with a European record of maximum temperature in 2021 of nearly 49˚C in Sicily. The average temperature over worldwide surfaces in 2021 was 0.84 degrees Celsius higher than that of the 20th-century, with a global land and ocean temperature 1.04˚C above the average. Scientists envisage that at the current rate of heating, the planet might reach the 1.5˚C increase in the 2030s, underscoring the global climate crisis. Rises in the amount of greenhouse gases in the atmosphere during the industrial revolution are mostly the product of human activity and are largely responsible for observed temperature increases; accountable amongst other for mass die-offs in coral reefs, and the decimation of coastal communities. As the globe struggles with climate-related heat waves, sustainable energy behaviours, or aspects of lifestyle, avenues need to be sought to reducing air conditioner demand, which accounts for a substantial portion of energy consumption in buildings. Ecological communities are commonly touted as a model for sustainable living because they have a strong environmental self-identity and values and are more likely to engage in environmentally friendly and energy-saving activities. However, it is questionable if members of these communities would behave as intended, particularly when faced with acute environmental conditions such as heat waves. Global energy consumption from air conditioners is anticipated to triple by 2050, as temperatures rise, and climate-induced extreme heat events become more frequent and intense. According to projections, AC installations will increase from 1.6 billion units in 2018 to 5.6 billion by 2050 [6]. This expansion will be driven mostly by fast growing economies experiencing higher temperatures and warmer years. According to energy demand scholars, reorienting behaviours toward pro-environmental cooling measures might generate massive energy and environmental advantages [7]. However, such increases are backed by people's own perceptions of the environment and driven by people's ever-demanding lifestyles [8,9]. Although promising, research utilising social science models to explain pro-environmental 2 behaviours has mainly focused on behaviours in the Global North, with only a few studies in the Global South. Despite this, cooling behaviours in the Global South are expected to contribute to increased future global cooling demand [10,11]. To this effect, there is a need to focus more explicitly on the motivations and behaviours underlying peoples’ ownership and use of ACs considering the rise in climate-induced heat events and changing weather patterns. Thus, through assessing energy performance and indoor comfort in places of worship, utilising free-running reference buildings, this study explores why a trend to install ACs in Baroque churches is emerging to deal with lifestyle and weather patterns. Therefore, the research questions can be summarised as follows: • To what extent are places of worship both traditionally and newly built conforming to indoor comfort levels in accordance with the EN16798-1 standard? • How do communities frequenting places of worship relate to the indoor comfort conditions for different seasons? • To what extent do passive building envelope measures and their prioritisation contribute towards improving the indoor building environment in places of worship and therefore avoiding the installation of mechanical air-conditioning systems? To answer the above questions, this thesis investigates the energy performance rating of five different representative churches and determine the relationship between the actual thermal comfort levels measured according to EN 16798-1 standard, the expected thermal comfort of attendees, and the effectiveness of selected passive measures. The key research contributions are cohesively published through Scientific Articles, to focus on: ▪ Research on building and construction methodologies for different eras such as vernacular architecture and modern sacred buildings. ▪ Software simulation (DesignBuilder-EnergyPlus) to determine the energy performance. ▪ Validation of software simulation results with actual data monitoring of temperature and humidity within a select number of representative places of worship. ▪ Qualitative Analysis of worshipers’ perception of indoor comfort, by means of questionnaires. 3 ▪ Modelling and evaluation of the best passive energy efficiency measures that can be applied to achieve an improved level of efficacy in new or renovated/retrofitted places of worship. Innovations and improvements recommended are presented in this thesis by compendium with due consideration to comfort vis-à-vis the increase in outdoor temperature, whilst considering responsible actions to reduce greenhouse gas emissions and respecting the buildings architectural heritage and artefacts with which they are adorned. The benefit of this study further benefits policy makers and experts to identify and assess harmonized strategies and policies to address Energy Performance and Indoor Comfort, enhancing both the environmental and economic effectiveness of these efforts. The research methodology is summarised through the following conceptual study framework. P3 •Scientific Article No.3 •‘Prioritising Passive Measures over Air Conditioning to Achieve Thermal Comfort in Mediterranean Baroque Churches’; Sustainability Journal 2022, 14, 8261 CP •Complementary Paper •‘Monitoring Indoor Temperatures of Places of Worship'; Engineering Sustainability & Sustainable Energy 2018 (ESSE ’18), ISBN: 978-99957-853-2-1 P1 •Scientific Article No.1 •A study of thermal comfort in naturally ventilated churches in a Mediterranean climate’; Energy & Buildings Journal, Volume 213, 2020, 109843, ISSN 0378-7788 P2 •Scientific Article No.2 •‘Thermal Comfort in Places of Worship within a Mediterranean Climate’; Sustainability Journal 2021, 13, 7233 •Thesis •Doctoral thesis by compendium in conformity to ANECA criteria 4 5 6 13 Figure 4: The Parish Church and Sanctuary of Our Lady of Graces in Zabbar. Left: The ceremony of the raising of the cross on top of the dome in 1928. Right: Photograph by author RCV (2022). Figure 5: Basilica of the National Shrine of the Blessed Virgin of Ta' Pinu, Għarb, Gozo. An architectural masterpiece built between 1920 and 1931 with superb sculptures and craftsmanship in Maltese Limestone. Photograph by author RCV (2022). This brief historical review of the growth of religious architecture in Malta highlights the church's leading role in Maltese life and demonstrates how the church has served as the fulcrum of activity in the Maltese community. In view of today's ecclesial and societal circumstances, this thesis emphasizes the relevance of the Church in supporting energy 14 savings, CO2 emissions reduction, and extra advantages coming from church building renovation. According to research, upgrading buildings to current energy efficiency and thermal comfort requirements is critical for enhancing sustainability and energy performance as well as preserving the architectural legacy of old structures [23,24]. However, amid all of these architectural studies, in-depth research into religious structures together with their distinctive occupancy and energy consumption, have only recently been conducted. 1.2 Developments Abroad Though active heating and cooling of churches is new in Malta, there was a rising worry among antiquarians and architects in Northern Europe in the 1960s where medieval stone cathedrals were suffering from acute overheating [25]. Heating was attributed to be the main cause of particle deposition on walls and vaults which led to damage being caused especially to wooden interiors and objects. Since 1887, a Directive was implemented which required that heating within churches in Sweden should be kept to a minimum and be provided only during services [1]. In this respect there were several conflicting opinions in Northern Europe on the requirement for heating in the 1960s and 1970s. The Swedish National Institute of Building Research ruled in 1967 that stone churches which weren’t initially designed to be heated should be left unheated [26]. Conversely, the management of the church does not appear to have been significantly impacted by this suggestion. On the contrary, it appeared that the 1960s was a time when several churches were permanently heated for the first time. A solution was a switch to intermittent heating rather than a total shutdown [27–29] Recent European studies have also investigated thermal comfort, measuring indoor temperatures and relative humidity (RH) levels. Loupa et al. provided findings from two medieval churches in Cyprus, demonstrating that changes in internal temperatures, humidity levels, and pollution levels surpassed suggested limits [30]. Varas-Muriel et al. investigated the San Juan Bautista Church in Talamanca de Jarama, Madrid, Spain, and discovered that the walls have varying levels of water absorption, which they attribute to the diverse types of construction used over centuries, weather conditions, and wall orientation [31]. Other 15 studies, such as that of Terill et al. established that through the application of insulation, ventilation and solar screen systems within church buildings, a reduction in the Solar Heat Gain Coefficient (SHGC) is evident [32]. Also, L. Bencs et al. conducted a study comparing the conventional, hot air heating systems in a mountain church within the village of Rocca Pietore in the Italian Alps. Results exhibited a considerable influx of external air through the hot air carried ducts [33]. Camuffo et al. investigated a novel heating system whereby a small amount of heat was supplied directly to the occupants within the pew area, such as to the feet, legs and hands, while leaving the overall conditions of the church undisturbed. This with the main aim to significantly reduce the risk of mechanical stresses in wooden artworks amongst other valuable artefacts whilst attaining occupant thermal comfort [34]. Research on Spanish rural churches resulted in a set of recommendations for the preventative maintenance of such ancient buildings while maintaining human comfort [35]. Because these structures, like those in Malta, were not initially intended or built for HVAC technology, temporarily installing systems to fulfil residents' thermal comfort was detrimental to the conservation of natural climatic conditions and churches' artistic and architectural legacy. Various works [36–38] demonstrate the connection between heritage comfort and thermal comfort, notably in heritage buildings and museums. In contrast, if moisture and mould development are not managed by conservation heating, dehumidification, and adaptive ventilation in a cold environment, the architectural history and artistic value of mediaeval churches may be lost [39]. If humidity and mould development are prevented, artistic treasures can endure in unheated churches for millennia [40]. Unfortunately, because mediaeval churches were initially built and used unheated for centuries, moisture damage is visible [41,42]. In this regard, research have been done in response to the rising concern about the potential negative implications of conventional heating. Expert opinion advised against their installation in churches in countries with extreme climates (particularly cold, humid winters), because they generate huge changes in the internal atmosphere and harm the conservation of church history [43–45]. Without temperature control, the internal climate in churches is mostly dictated by the external environment and the hydrothermal performance of the building envelope. 16 The European project “Friendly-Heating: comfortable for people and compatible with the conservation of artworks preserved in churches”, addressed the issues caused by continuous or intermittent heating of historic churches, which disrupts the microclimatic conditions to which the building and the artworks preserved inside have acclimatized [46]. Because thermal comfort and artwork preservation frequently clash, a compromise between the two demands is required. The proposed heating approach is to supply a little quantity of heat directly to persons in the pew area while leaving the church's macro conditions unchanged. This unique heating system is based on several low-temperature radiant emitters set in a pew to offer a suitable distribution of heat to those occupying that space's feet, legs, and hands. This new approach not only considerably decreases the risk of mechanical stress in wooden artworks and panel or canvas paintings, fresco soiling, and cyclic dissolution-recrystallization of soluble salts in the masonry due to limited heat dispersion, but it is also energy-efficient. At the Santa Maria Maddalena church in Rocca Pietore, Italy, extensive environmental monitoring was done over a three-year period to compare the performance of the new heating system to that of the old warm-air system [34]. Three draft standards of the European Committee for Standardisation designed for use in the investigation and management of settings of cultural heritage items contain the methodology and findings of this extensive and diverse study. Surprisingly, the Mediterranean area has extremely few research or publications that discuss religious facilities. Studies were mostly done for churches in the cool-summer humid environment of Western Europe or for mosques in the hot-humid climates of the Eastern Region (it should be noted that unlike churches, mosques do not feature works of art such as paintings). As a result, the findings' relative efficacy is typically not relevant to the local situation, where the building style is different and cooling rather than heating is of a primary concern because of the region's predominately hot environment. 1.3 European Energy Directives and Places of Worship It is crucial to make the connection between thermal comfort and places of worship because it may be viewed as a physical depiction of the inner serenity that visitors to these temples 17 have long sought. Despite having different architectural styles, churches all have comparable occupancy trends. There is a sizable gathering area in each of these places of worship, used intermittently with attendance ranging from minimal and almost full. The remainder of the time shows little to no occupancy. Due to the reduced total energy intensity (measured in yearly kWh/m2) caused by the occasional occupancy, typical energy efficiency measures (EEMs) frequently have longer payback periods and are therefore not always cost-effective [47]. However, the world's reliance on energy has been growing at a concerning rate. The International Energy Agency (IEA) estimates that the global energy consumption rose by 92% between 1971 and 2014 [48]. A major amount of this growth has come from the building industry. In reality, the construction industry including operational emissions was responsible for 35% of all energy use and more than 38% of worldwide greenhouse gas emissions in 2020, according to the 2020 Global Status Report for Buildings and Construction [49] Malta is attempting to lessen the consequences of climate change and create a uniform energy strategy within the EU. The European Heads of State or Government adopted binding objectives to enhance the percentage of renewable energy as part of this strategy in March 2007. In order to meet the 2020 objective of renewable energy, it is imperative to intensify efforts on all fronts, according to Malta's Renewable Energy Action Plan (NREAP). Malta and the other members of the European Union have come to an agreement on legally enforceable national goals for raising the proportion of renewable energy in order to reach a 20 percent Union-wide share by 2020. Due to the rise in oil prices in 2008, the global economic crunch, and the unpredictability of the tourist sector, the urge imposed by national and EU regulations was further accelerated, leading to 22.1% renewable energy out of the total energy used in the EU in 2020 [50]. The energy union strategy (COM/2015/080), published in March 2015 [51], outlines the EU's initial steps toward sustainable energy and aims to create a union that gives European consumers, households, and businesses access to safe, sustainable, competitive, and reasonably priced energy. In order to promote the shift away from fossil fuels and toward cleaner energy sources, and to fulfil the EU's Paris Agreement goals to reduce greenhouse gas emissions, the EU finished a thorough reform of its energy policy framework in 2019. This led 18 to an agreement on a new set of energy regulations known as the "Clean Energy for All Europeans package," which proved an important step to put the 2015 energy plan into practice [52]. The EUCA Regulation, also known as EU Regulation 2018/1999 on the Governance of the Energy Union and Climate Action, was approved in 2018. This laid the groundwork for the legal framework, the governance framework, the strategies, and the policies necessary to fulfil the objectives of the energy union and the long-term EU greenhouse gas emission obligations (consistent with the Paris Agreement). Malta, like every other EU Member State, established a 10-year integrated National Energy and Climate Plan (NECP) for the years 2021–30 in accordance with the EUCA Regulation and with the goal of meeting the EU's energy and climate target to reduce greenhouse gas emissions levels by 2030 [53]. Malta's contribution is set at 10% in the NECP's list of individual national overall objectives for the proportion of energy from renewable sources in gross final energy consumption in 2020. Additionally, EU leaders decided to establish an ambitious goal in December 2020 to reduce greenhouse gas emissions by 55% (compared to 1990 levels) by 2030. The Clean Energy for All Europeans package, which was based on suggestions from the EU Commission issued in November 2016, consists of eight legal acts passed between May 2018 and May 2019. The new regulations are anticipated to have a significant positive impact on consumers, the environment, and the economy. They will also make a significant contribution to the EU's long-term plan to become carbon neutral by 2050 [54]. The European Green Deal [55], an ambitious set of policies that should allow European residents and companies to profit from a sustainable green transition, aims to make Europe the first climate-neutral continent by 2050. Each Member State must expand its production and usage of renewable energy for electricity, heating, cooling, and transportation if they are to reach this shared goal. Although Malta's annual energy usage is less than 2,500 GWh, demand for electricity is growing due to the country's expanding population, economy, and tourism. In recent years, Malta has attempted to upgrade and diversify its electrical system, moving away from inefficient coal and heavy oil-fuelled electrical generation to one based on natural gas, with oil serving as a backup, and an electricity interconnector to Sicily, Italy. The next phase is a €322 million Malta-Italy gas pipeline, which the government hopes to have 19 operational by 2024 [56] and replace the permanently moored natural gas ship that now supplies the power plant. Renewable energy sources play a crucial role in the battle against climate change, but they also boost economic growth and energy security at the national level. Government agencies and Maltese professional organisations have undertaken a number of attempts in recent years to increase public understanding of renewable energy uses and, to a lesser extent, of energy conservation and efficiency. Additionally, financial incentives for purchasing renewable energy systems were implemented. Numerous medium-sized and big organisations have chosen to update their energy profiles as a result of this and the rising cost of energy and services; however, no standard methods have yet been implemented to guarantee the greatest possible benefit to the client and the environment. Additionally, up until now, this industry has relied heavily on subsidy programs, supported by both the national government and the EU. Studies pertaining to building energy efficiency, on the other hand, remain poor and sporadic. This is especially true for places of worship, where the legacy and historic architecture serve as proof of civilisation. EPBD exempt “buildings and monuments officially protected as part of a designated environment or because of their special architectural or historic merit, where compliance with the requirements would unacceptably alter their character or appearance” [57]. Nevertheless, there is a recent trend in Malta whereby churches are being installed with invasive AC units to address the hot summer indoor environments, which may jeopardise the conservation of the respective church’s cultural assets. 1.4 Sustainable Energy and the Church The concept of net zero energy buildings is gaining hold in many parts of the world, including all EU Member States, since buildings provide great possibilities for energy savings at reasonable rates. Electricity consumption in both the domestic and commercial sectors has been registered on the increase year after year [54]. Concurrently, electricity consumption scenarios are changing with new pricing policies, stricter EU directives such as Directive 20 2010/13 and time bound incentives to encourage consumers and entrepreneurs to invest and own renewable energy systems [58]. With the Pope's encyclical letter Laudato Si' from April 2015 [59], the Roman Catholic Church, too, raises concerns about what is happening to our shared home. Pope Francis encourages everyone and not only Christians to recognise “the rich contribution which the religions can make towards an integral ecology and the full development of humanity.” 'Ecological Education and Spirituality,' the concluding chapter of Laudato Si', welcomes everyone to the heart of ecological conversion. The importance of environmental education cannot be underestimated. In line with the teachings of Laudato Si’, numerous States gathered in New York in April 2016 to sign the COP21 Paris Agreement on Climate Change. As a result, all stakeholders agreed that the era of fossil fuels is ending, and that it is time to focus more on energy efficiency and renewable energy, in all structures, and for all human activities [60]. 1.5 Thermal Comfort vs Artworks Preservation The adoption of temperature regulation stems from the need to balance various factors which promote inadequate climate control in places of worship. These factors may include amongst others, human comfort, energy costs, damage, and long-term viability. Temperature fluctuations are the underlying cause of damage to materials which expand as their temperature rises and shrink as it declines. Repetitive fluctuations can give rise to fatigue cracking. Though most artefacts are many times not sensitive to such fluctuations, particularly at micro-level, the analysis of the risks from temperature fluctuations is complex and many uncertainties remain [61]. Even where it is not visible, water is to be found almost everywhere. Damp in buildings can originate from roof, foundations, or exposed walls. Although rising damp is a typical problem in churches, if moisture is removed from wood, ivory, or bone, they shrink and are prone to break and warp. Similarly, laminar organic goods like paper, parchment, leather, and natural fabrics lose flexibility and become more brittle. In general, materials that contain moisture become brittle below 40% RH. On the other hand, in extremely wet environments, with above 65 to 70% RH, mould grow, and metals corrode. 21 Additionally, biodeterioration is more pronounced and colours fade more quickly at high RH [62]. Usually, churches are exposed to dampness which is easily absorbed by warm air. This phenomena is experienced when the congregation departs and the church is in turn closed, forcing the temperature to drop [63]. Water condenses on any surface below the dew point of the air, which itself may be near saturation. When this water from the wall evaporates, the water inevitably carries salts, which then crystallise as efflorescent. Efflorescence can appear on top of or underneath the paint surface. The latter is more of a concern since when the wall dries, the evaporation zone moves inwards. Condensation can dissolve contaminants in the air and redissolve efflorescence, and it may do so both above and below the surface. Each cycle produces more damage, hence cyclic heating and cooling circumstances should be avoided [64–68]. Paintings on the wall are safest when they are dry, or at least not absorbing moisture from the environment. As documented in the Parish Church of the Annunciation of Our Lady, Birgu (Vittoriosa) by the author during this period of report, fluctuations in indoor environments affected relative humidity stability, and as a result, efflorescence as well as plaster blistering and detachment in the inside walls, drying and cracking in the timber, and disaggregation in the stone were evident (refer to Figure 6). 22 Figure 6: The Parish Church of the Annunciation of Our Lady, Birgu (Vittoriosa). Photographs by author RCV (2016). The course of action advised is to manage the microclimate for human comfort within churches, in particular those decorated with art and artifacts, without changing the macroclimate. Churches frequently serve as more than simply a place of worship; they are decorated with distinctive architectural features and works of art (refer to Figure 7). When it comes to heating, Bordass utters, that the main objective of assessing the internal microclimate of churches is to gauge and enhance users' comfort [69]. But the strategy should be "Heritage First," with emphasis on creating the ideal microclimates for the preservation of 29 Figure 12: St John's Co-Cathedral, Valletta. Photographs by author RCV (2022). Top: The painting representing the Beheading of Saint John the Baptist (1608), by Caravaggio. Bottom: The Grand Masters’ Crypt. 30 While enrolled in this PhD program, the author (RCV) was responsible of the St. John's CoCathedral Museum's ongoing development as Site Technical Officer. The new museum (refer to Figure 13) is intended to house the artifacts now held in storage. The restoration of the Bartolott Crypt, the creation of a new Tapestry Chamber, and the creation of the Caravaggio Wing, along Merchants Street, are all included in these expansion works. The project of restoring and constructing new areas entails interventions on one of Malta’s most historically important monuments. Extensive research and investigations were conducted to ensure that no historical fabric is lost. All works are being conducted under the supervision of the Superintendence of Cultural Heritage (SCH) in liaison with various consultees, including the United Nations Educational, Scientific and Cultural Organisation (UNESCO). In Fabbri et al. [36] and Corgnati et al. [38], where Indoor Microclimatic Quality (IMQ) and Indoor Environmental Quality (IEQ) are compared, the parallel between heritage comfort and thermal comfort is described. The contradiction between visitor comfort and artifact conservation in museum structures like churches has also been demonstrated by La Gennusa et al. [37]. The key findings from the various research investigations conducted on the subjects Figure 13: The St John’s Co-Cathedral Museum Project, Valletta. Courtesy of the St John’s Co-Cathedral Foundation. 31 of thermal comfort, indoor air quality, and energy consumption are summarized in more recent studies [69,72]. Results show how serious the problem is. According to the collected data, significant changes in interior settings largely impact temperature (T) and relative humidity (RH), which cause plaster to blister, crack, and detach. The extensive oratory repair and conservation effort at St. John's Co-Cathedral in Valletta provides proof of this (refer to Figure 14). The apse's stone gilt carvings of the arch and ceiling as well as its mural paintings, which were done in both oil on canvas and oil on stone techniques, were restored. The project was challenging because of the wide range of creative methods and materials used in the creation of these numerous artifacts, as well as the intricate patterns and degrees of decay that were present. In order to ensure the preservation of this piece of art for the benefit of both present and future generations, it was necessary for specialists from several fields to work together transdisciplinary. 32 Rising damp is also of a major concern in assessing Energy Performance and Indoor Comfort in Places of Worship. It is very important when considering rising damp to take into consideration the geology of the Maltese islands and the relation of the church building under review with the mean sea level, subterranean structures, orientation, distance from coastline and water features amongst other. Groundwater flow from these groundwater bodies might be caused by aquifers, faults/cracks, and rock matrix porosity [64]. It is also important to bear in mind that until around 150 years ago, only those who died of infectious illnesses or executed convicts were buried in cemeteries. To keep their dead close and on holy ground, Figure 14: The Oratory Restoration Project. St John's Co-Cathedral, Valletta. Photographs by author RCV (2021). 33 people interred their family members in the cathedrals, chapels, and crypts of their cities and villages. It is only after the plague that struck Malta in May of 1813 through January of 1814, resulting in a death count of nearly 5,000 people, that burial practices were forced to change [73]. Only following the devastating plague, Burials Ordinance dated 10th May 1869, prohibited the burial of corpses within churches and to make other provisions in connection therewith [74]. Damp pertaining to fresh or sea water arising in historical buildings, including churches, is a well-known phenomenon that varies by region, many times leading to serious conservation issues. The phenomenon and the resulting decay have been extensively studied [75]. Nevertheless, it is pertinent to note that building masonry units and methodologies vary from one location to the other. These masonry materials, respond differently to the rising damp phenomenon, with varying mechanisms and contributing factors to water absorption, and this behaviour cannot be generalised. The varying characteristics of the building methodology, together with site conditions and ambient surroundings require specific evaluation that many times vary from one church to the other in Malta, let alone from one country to another. Rising damp is still one of the most frequent problems affecting historic masonry buildings worldwide because it compromises the performance of the building envelope, the health and comfort of the occupants, and the materials integrity. The problem of damp removal remains largely unsolved despite the significant effort made over the past century to understand the phenomenon of water capillary rise, as not only do the technologies used in the field frequently fail, but their operating principles in actual masonry have not yet been fully clarified. The Museum Project at St. John's Co-Cathedral in Valletta (refer to Figure 15) has successfully identified the complex relationship between indoor comfort, construction material specifications, the various characteristics of the building methodology, site conditions, ambient surroundings, and the historical rubble fills that were once a burial ground. 34 Another important aspect to bear in mind is the shortage of rainfall. According to data from the Meteorological Office of the International Airport of Malta based on the 1981-2010 period, a regular winter’s yield of rainfall is 254.6mm. However, annual precipitation for the last two years (2020/2021) combined saw only 207.8mm of rain hit the island. With a yield between 250mm and 500mm of annual rainfall, Malta’s climate is defined as semi-arid, while if precipitation persists below 250mm, the climate becomes that of a desert. This water shortage has affected Malta’s history and even architecture. Thousands of reservoirs were excavated and built throughout Malta and Gozo over centuries to collect and store rainfall. In times of drought or siege, they supplied a lifeline to Malta's people and remain a source of pride for the Maltese. An example of a large potable freshwater reservoir is shown in Figure 16. Nevertheless, these too can become a source of upward movement of moisture through building materials by capillary action, if not properly maintained. The rise is also dependant Figure 15: The St. John's Co-Cathedral Museum Project, Valletta. Photographs by author RCV (2022). 35 on the masonry specifications; with horizontal “bridging”, gravity or condensation being the main causes of dampness in walls. Figure 16: Luqa Reservoir; known as the ‘sunken cathedral’, constructed at around 1907. Courtesy of the Malta Water Services Corporation. 36 CHAPTER 2: METHODOLOGY 2.1 Reference Buildings As in the Maltese Islands, there are 359 churches, with a density of around one per square kilometre, it proved unfeasible to conduct an indoor comfort study for each church throughout this period of report. Therefore, a smaller representative number of churches, known as "reference buildings" (hereafter referred to as RBs), comprising most kinds of typical churches in Malta, were analysed in order to investigate the church building stock (refer to Table 1). RBs were chosen based on "actual example" structures with typical physical and occupational traits for each of the investigated church. The building stock categories were derived according to the location, construction period, building size and shape RB classification approach, as proposed by Ballarini et al. [76]. Given the limited size of the Maltese Archipelago (with an area of just 316km²), distinct Mediterranean climate and the geographic position, one climatic classification zone address all RB climatic parameters. Consequently, the key categorization criteria were as follows: • 17th to mid-18th century Baroque period, • mid-20th century neo-Romanesque style architecture, and • late 20th century (post Vatican Council II style) modern architecture. The Stella Maris Parish Church in Sliema and the Annunciation Parish Church in Balzan are examples of typical urban inland size churches from the 17th to the 18th centuries. The St. Joseph Parish Church of Msida is under the same construction type but is situated by the sea and has a significantly larger floor area and volume. The typical mid-20th century neoRomanesque style church is Santa Venera Parish Church in Santa Venera, whereas the modern structure is Our Lady of Mount Carmel Parish Church in Fgura. These five churches are all recognized on the National Inventory of the Cultural Property of the Maltese Islands 37 and scheduled by the Planning Authority as Grade 1 monuments (NICPMI). Photographs depicting each church building and tabled specifications follow. Table 1: Physical characteristics of the church buildings under study. Church Location Opening hours Envelope U-value (W/m²K) Internal heat capacity (KJ/m²K) Thermal diffusivity (m²/s) Window to wall ratio Floor area Surface area (m²) and air volume (m³) System Glazing area open (%) The Annunciation Parish Church, Balzan Inland MonFri: 6:009:00am, 18:0020:00pm, Sat 6:00-9:00am, 17:0020:00pm, Sun 6:00-13:00pm, 17:00-20:00 pm External wall 0.54 180 11.44x10-7 N=3.6% 718m2 1:2.25 (Sur. Area 3308m2 & Vol. 8337m3) Naturally & Mechanically Ventilated 0% Glazing 6 3.4x10-7 S=3.6% Floor 1.92 154 2.42x10-6 E=3.6% Roof 2 180 9.69x10-7 W= 3.6% Stella Maris Parish Church, Sliema Inland MonFri: 6:009:00am, 18:0020:00pm, Sat 6:00-9:00am, 17:0020:00pm, Sun 6:00-13:00 pm, 17:00-20:00 pm External wall 0.49 180 11.44x10-7 N=2.6% 375m2 1:2.5 (Sur. Area 2490m2 & Vol. 5415m3) Naturally & Mechanically Ventilated (ACs installed on 19/05/2018) 20% Glazing 6 3.4x10-7 S=2.6% Floor 2.55 200 2.42x10-6 E=2.4% Roof 2.33 180 9.69x10-7 W= 2.4% St. Joseph Parish Church, Msida Seaside MonFri: 6:009:00am, 18:0020:00pm, Sat 6:00-9:00am, 17:0020:00pm, Sun 6:00-13:00pm, 17:0020:00pm External wall 0.49 180 11.44x10-7 SW = 7% 1261.5m2 1:3 (Sur. Area 4525.2m2 & Vol. 15,239m3) Naturally Ventilated 0% Glazing 6 3.4x10-7 SE = 2% Floor 2.54 200 2.42x10-6 NW = 6% Roof 2.2 180 9.69x10-7 NE = 7% Santa Venera Parish Church, Santa Venera Inland MonFri: 6:009:00am, 18:0020:00pm, Sat 6:00-9:00am, 17:0020:00pm, Sun 6:00-13:00pm, 17:0020:00pm External wall 1.8 180 13.71x10-7 SW = 0% 1137m2 1:5 (Sur. Area 4136m2 & Vol. 19,682m3) Naturally Ventilated 0% Glazing 6 3.4x10-7 SE = 11% Floor 2.07 200 2.42x10-6 NW = 0% Roof 1.03 120 9.69x10-7 NE = 11% Our Lady of Mount Carmel Parish Church, Fgura Inland MonFri: 6:009:00am, 18:0020:00pm, Sat 6:00-9:00am, 17:0020:00pm, Sun 6:00-13:00pm, 17:0020:00pm External wall 2.52 227 7.6x10-7 N=18% 661.4m2 1:3 (Sur. Area 2185m2 & Vol. 7446m3) Naturally Ventilated 23.5% Glazing 6 3.4x10-7 S=18% Floor 2.24 200 2.42x10-6 E=18% Roof 2.52 227 7.6x10-7 W=18% 38 In order to arrive to a significant analysis of the architecture, structural detailing, paintings, and other works of art in relation to environmental conditions, artistic and architectural heritage, Melitensia publications and dissertations were thoroughly reviewed at the University of Malta. In contrast to studies on energy use or indoor comfort, the majority of them were Master's thesis and dissertations from the Faculty of Arts that focused on artworks and historic church architecture. Reference was also made to a number of other works, including books [77–80], feast programs, reviews of exhibitions, newspapers, church archives, Archiepiscopal, and National Archives. Unfortunately, not much information was available in these archives. Other than a recent undergraduate engineering dissertation to estimate the air-conditioning capacity needed for Stella Maris Church [81], no research dealing with energy performance in churches or other places of worship have been located in Malta. However, actual first-hand knowledge was gathered from people who were somehow connected to the history of Maltese churches or the specific building or upkeep of churches in Malta, in particular for the five selected reference churches. 2.2 Our Lady of the Annunciation Parish Church, Balzan Balzan was established as a parish on August 14, 1655, and construction on the current Parish Church began in December 1669 (refer to Figure 17). The edifice was partially in use after four years of construction, according to a source, but Lorenzo Gafa and Giovanni Barbara, the architects, finished the work by 1695. A Latin cross design was used in the construction of the church. Also included in 1708 was a belfry, which now houses 6 bells produced by Fonderie Paccard in Annecy, France. Construction was done primarily with load-bearing masonry walls that supported a vaulted roof and dome structure made of globigerina limestone blocks and covered with a layer of "deffun." The "deffun" technique involves laying out a variety of graded gravels (from large, rough grains to fine, thin grains), followed by a layer of lime, and overlying coating of beaten, crushed pottery (clay) powder. 45 Figure 20: Santa Venera Parish Church, Santa Venera. Photographs by author RCV (2018-21). 46 2.6 Our Lady of Mount Carmel Parish Church, Fgura The Parish Church of Fgura was constructed in the latter half of the 20th century (1988), and on February 1, 1990, it was dedicated to Our Lady of Mount Carmel. It was the brainchild of structural engineer (Perit) Godfrey Azzopardi and architect (Perit) Victor Muscat Inglott. This church is one of the most inventive and daring reinforced concrete constructions on the Island. It is constructed in a contemporary, post-Vatican II Council style (refer to Figure 21). Its layout is square, and a concrete shell construction that is symmetrical around both axes cover the top. Concrete serves as the primary structural component of the building, and the shape of the building rather than its sheer mass gives it strength. The structure appears to be floating due to its pyramidal external design and four triangle openings on each of its four sides. 47 Figure 21: Our Lady of Mount Carmel Parish Church, Fgura. Photographs by author RCV (2018-21). 48 2.7 Construction Methodology and Local Distinctiveness The Maltese Islands can be distinguished by their sedimentary geology and strategic location in the centre of the Mediterranean. With the whole capital city of Valletta and the megalithic ancient Temples being designated as World Heritage monuments by UNESCO, "franka" (as known in Maltese) or "softstone" is by far the most common local construction material. The Oligo-Miocene "soft limestones" found widespread in the Mediterranean Basin include the Globigerina Limestone Formation. It is the most prevalent formation in the Maltese Islands and is made up of a medium to fine-grained stone that is yellow to greyish and predominately composed of planktonic foraminifera (Globigerina) [83]. The Lower Globigerina Limestone, Middle Globigerina Limestone, and Upper Globigerina Limestone are the three components of this Globigerina Limestone Formation (refer to Figure 22), and two phosphatic hardgrounds separate them [84]. The oldest element, Lower Globigerina Limestone, has long served as the primary construction material in Malta. Figure 22: Geological map of the Maltese Islands. The two primary porous and fissured limestone formations are the Globigerina-Lower Coralline Limestone and the Upper Coralline Limestone. The Blue Clay formation, which is occasionally covered by the Greensand formation, is a relatively thin layer of clayey and marly material that separates them. The Globigerina Limestone only serves as an aquifer locally, 49 where it is heavily fractured, while the Upper and Lower Coralline Limestones are thought to serve as aquifer rocks [85]. Presently, the construction industry in Malta is facing severe challenges with respect to supply of good quality limestone for specific applications. The concern that natural resources, such as land and stone, are finite, is a tangible problem. In recent years, Malta has grappled with the problem of disposing of construction waste, with the industry also facing changes due to Malta’s traditional Franka (Globigerina Limestone), increasingly becoming a scarce resource. Nevertheless, the Maltese limestone is still shaping the architecture of the islands even where churches are concerned. For the past six years, stonework (including intricate works) has been ongoing at the back of the Parish Church of Our Lady of Loreto in the village of Għajnsielem on the sister island of Gozo (refer to Figure 23). The foundation stone of this Roman Catholic neo-gothic parish church was laid on 14 September 1924 on the design of architect Ugo Mallia; nevertheless, the church was not completed until the mid-1970s due to a number of interruptions, with the sacristies never completed at all. During this period of report these two sacristies are being built in limestone on either side at the back of Għajnsielem parish church (refer to Figure 24). Figure 23: Plan of the Parish Church of Our Lady of Loreto in the village of Għajnsielem, Gozo. 50 Given the extensive use of Globigerina Limestone in Maltese human culture, the Executive Committee of the International Union of Geological Sciences (IUGS), through its Heritage Stones Sub-commission (HSS), led by Prof. Dolores Pereira of the University of Salamanca (Spain), has approved the designation of Maltese Globigerina Limestone in 2019 as a Global Heritage Stone Resource (GHSR) [86]. Figure 24: Ghajnsielem Parish Church (Gozo, Malta). Photographs by author RCV (2022) 51 2.8 Masonry to Concrete Structures With the fusion of mass and tension found in the arch and arcade, it is perhaps not surprising that reinforced concrete became with time used for building contemporary churches. The idea of reinforced concrete as a frame construction, capable of bridging great spans and window openings because it worked in tension as well as compression, was a boon for factory construction, but its decorative potential was also proven in church architecture. This was brought with the Ateliers d'Art Sacré, an artistic movement based in Paris in the first half of the 20th century, that united artists, architects, and craftsmen to bring art that was aesthetically challenging as well as devotional into churches [87–90]. In Malta too, concrete pre-cast slabs for roofing and mass concrete structures were introduced in the 20th century. Reinforced concrete had an important role in the Roman Catholic churches built in the postwar years. Apart from Our Lady of Mount Carmel Fgura Parish Church, considered in this thesis as one of the RBs, other extraordinary uses of reinforced concrete for religious buildings in Malta are portrayed in St. Francis of Assisi Qawra Parish Church, in San Pawl il-Bahar (refer to Figure 25), and the Convent & Sanctuary Church of St. Therese of Lisieux, in Birkirkara (refer to Figure 26). 52 Figure 25: St. Francis of Assisi Qawra Parish Church, San Pawl il-Bahar. Photograph by author RCV (2021). Figure 26: The Convent & Sanctuary Church of St. Therese of Lisieux, Birkirkara. 53 2.9 Onsite Measurements and Logging Systems To address the performance of selected reference buildings, measurements of air temperature (T) and relative humidity (RH) with data loggers were conducted in various locations, ranging from the western end, the nave, and the altar. The loggers were placed at a height ranging from circa 1.7m to 3.5m from the finished floor level (FFL). Table 2: Location of Sensors - Vertical height Dual channel digital air humidity and temperature sensors (HOBO data loggers) were placed along the main nave at a height that corresponds the actual environment that churchgoers encountered while avoiding the impact of radiating sources and air movement, in order to acquire representative climatic data. At intervals of five minutes, the loggers recorded the indoor and outdoor temperature T (°C) and air humidity RH (%), with data being gathered on a monthly basis. The recorded data were wirelessly transferred to mobile devices using Onset's HOBO MX1101 data recorders using Bluetooth Low Energy (BLE) technology and tabulated in excel format [91]. After any data outliers were removed, recorded values were then converted from 5-minute intervals to the corresponding mean hourly values. Parish Church Western End Nave Altar (m) (m) (m) Balzan 2.0 2.4 1.8 Stella Maris 2.3 3.5 1.7 Msida 3.0 3.2 2.0 Fgura -* 3.0 2.5 Santa Venera 2.0 2.0 2.4 *Due to the church layout, one sensor is covering both the Western End and Nave 54 Table 3: Specifications of Data Logger Temperature Sensor Range -20° to 70°C (-4° to 158°F) Accuracy ±0.21°C from 0° to 50°C (±0.38°F from 32° to 122°F) Resolution 0.024°C at 25°C (0.04°F at 77°F) Drift <0.1°C (0.18°F) per year RH Sensor* Range 1% to 90%, non-condensing Accuracy ±2.0% from 20% RH to 80% RH typical to a maximum of ±4.5% including hysteresis at 25˚C (77˚F); below 20% RH and above 80% RH ±6% typical Resolution 0.01% Drift <1% per year typical *As per RH sensor manufacturer data sheet. 2.10 Adaptive Comfort Model Standards for thermal comfort in use are either based on heat balance or adaptable models. Both the Adaptive Comfort Model and the Heat Balance Model (PMV/PPD Model) are included in the EN 16798-1 standard. According to EN 16798-1 [92], the adaptive comfort model should be used for buildings without mechanical cooling, whereas the PMV/PPD Model is appropriate for structures that are mechanically heated and/or cooled (naturally ventilated). The PMV/PPD Model is a heat balance model which investigates thermal physiology while assuming precisely analysed factors such as activity level, clothing's thermal resistance, air 61 38 48 58 68 78 88 98 07-Dec 11-Dec 15-Dec 19-Dec 23-Dec 28-Dec 01-Jan 05-Jan 09-Jan 14-Jan 18-Jan 22-Jan 26-Jan 30-Jan 04-Feb 08-Feb 12-Feb 16-Feb 21-Feb 25-Feb 01-Mar 05-Mar 09-Mar 14-Mar Humidity (%) Date Nave Humidity Fluctuations Fgura Santa Venera Stella Maris Msida External Balzan 9 11 13 15 17 19 21 23 07-Dec 11-Dec 15-Dec 19-Dec 23-Dec 28-Dec 01-Jan 05-Jan 09-Jan 14-Jan 18-Jan 22-Jan 26-Jan 30-Jan 04-Feb 08-Feb 12-Feb 16-Feb 21-Feb 25-Feb 01-Mar 05-Mar 09-Mar 14-Mar Temperature (°C) Date Nave Temperature Fluctuations Fgura Santa Venera Stella Maris Msida Balzan External Figure 28 - Comparative Analysis of Nave Temperature (T °C) Fluctuations of the five churches under study. Figure 29 - Comparative Analysis of Nave Humidity (RH %) Fluctuations of the five churches under study. 62 The baroque churches under consideration feature substantial globigerina limestone walls. The wall's thickness provides strong thermal insulation, preventing the inside temperature from being impacted by the building's daily/hourly temperature changes. Additionally, the hygroscopic building fabric buffer the RH as it absorbs and desorbs moisture from the air, as long as the air within the church is not rapidly exchanged with the outside air [110]. On the contrary, modern churches such as that of Fgura exhibited low temperature and high relative humidity for the measured period in winter, and both parameters are considered to go out of the comfort zone. Due to these phenomena and supporting results from this study, one must promote passive control methods and, concurrently ensure that the environment has no impact on the structure and objects decorating our churches. As most of the historic structures on the island fit the category of baroque churches, the results from the complementary paper were indeed a real eye-opener to those present at the Engineering Sustainability & Sustainable Energy 2018 (ESSE ’18) conference organised by the Chamber of Engineers in collaboration with the Institute for Sustainable Energy of the University of Malta. All professional stakeholders present acknowledged that considerable opportunity exists to leverage the benefits of energy-efficient retrofitting. This prompted further studies to explore future strategies for creating a sustainable future in a world experiencing energy difficulties. The information in this paper is based on scientific data gathered to reveal the efficacy of temperature control recommendations that result from a confluence of human comfort needs, a paucity of science, a substantial number of assumptions, and an unfortunate propensity to generalize to a single rigid target. There are still a lot of unknowns in the examination of temperature-related dangers. Such presumptions must be contested in an era of growing concern over the prudent use of our planet's resources. The question becomes, where and how should one focus temperature control efforts, and why? Sustainable cities call for sustainable solutions, but this study highlights how increasingly unsustainable more modern churches are. This emphasizes the value of adhering to current standards and certification throughout the entire building development life cycle as well as the use of techniques and technologies in the effort to renovate and retrofit buildings in order to significantly reduce energy consumption while maintaining an acceptable level of comfort. 63 Malta is obliged under the Energy Efficiency Directive to establish national building renovation policies, including eco-refurbishing public structures, many of which have historical significance. Although restoration of historic structures is gaining popularity in Malta, the significance of energy-efficient renovation is yet largely unexplored, and thus an in-depth study, utilising the EN 16798-1 adaptive comfort model was taken up, the outcome of which is portrayed in Scientific Article No.1. 3.2 Scientific Article No.1 Scientific Article No.1 entitled ‘A study of thermal comfort in naturally ventilated churches in a Mediterranean climate’; published by Energy & Buildings Journal [2], conducts a comparative analysis of the five selected churches to determine their respective level of indoor thermal comfort throughout the year (2018) using the EN 16798-1 adaptive comfort model with category III comfort limits. In this research, the adaptive comfort model was adopted, as opposed to the PMV/PPD model, as it provides more flexibility on the optimal indoor temperature conditions when compared with the outdoor ambient temperature, particularly in natural ventilated churches. In addition, this model is founded on the hypothesis that occupants within naturally ventilated buildings attain thermal comfort within a wider range of indoor temperatures when compared with occupants within HVAC controlled environments. In fact, over the past 20 years, it has been established that there was a shift from heat-balance based thermal comfort models towards adaptive comfort models [111]. In this case, since the environments within the RBs had low air velocities and provided that the mean radiant temperature and the air temperature recorded similar readings, the latter was considered as a sufficient indicator of thermal comfort. Moreover, category 3 was chosen as the optimal limits of comfort which is termed as “an acceptable, moderate level of expectation and may be used for existing buildings” [92]. Monitoring of indoor and outdoor temperatures and humidity, using HOBO calibrated sensors located along the main nave and situated at a defined height which corresponds to the level of the occupants, was conducted for all five RBs simultaneously for the year 2018. The five- 64 minute interval readings were transposed to hourly values, and an analysis of the design and typical weeks across all four seasons was conducted. From the analyses conducted it was determined that the thermal mass of buildings have a significant influence in managing indoor temperature in these free-running structures. The Baroque churches demonstrated to have an overall high thermal mass when compared to the mid-20th century neo-Romanesque style architecture, and late 20th century (post Vatican Council II style) contemporary architecture, resulting in a steadier indoor temperature in Baroque churches as compared to higher fluctuations in temperature for the more recent architectural styles. An extract of the results for all five RBs are graphically interpreted in Figures 30 to 34. The behaviour portrayed between the Baroque and the contemporary churches is mainly attributed to the lack of overall thermal mass of the contemporary buildings and higher solar gains through glazed elements, providing minimal "inertia" against external temperature fluctuations. The fundamental difference lies within the building envelope, which is composed primarily of masonry blocks (high thermal mass) having walls that are between 1.5 and 2 meters thick for the Baroque churches. This results in minimal heat transfer (U-value) across the building, which prevents fluctuations in the inside temperature. Furthermore, as compared to the more contemporary construction methodologies, the proportion of glazing to wall area in Baroque churches is negligible, making up only 3% of the entire external surface area of the church. Results also highlighted that out of the two contemporary churches, the Santa Venera parish church exhibited the highest internal temperatures on average. This is due to the fact that the absolute total area of glazing is higher in Santa Venera parish church, even though the Fgura Parish Church has a higher percentage of glazing. Glass by itself has a very low thermal mass value, but it also lets solar radiation to flow through, hence causes the indoor space to overheat, especially in the summer. Thus, the indoor ambiance is aggravated by the fact that the windows are facing south-east and south-west, which are the most critical directions that contribute to highest solar radiation infiltration in the late morning and early afternoon hours, when the solar radiation is relatively high and falling directly on the windows and walls. In addition, amongst the churches under study, Santa Venera parish church is the only one whereby the antiporta (that is a door placed behind the main door to create a small porch) is 65 missing, which results in natural infiltration causing induced significant fluctuations in the indoor environmental conditions during service hours. The results achieved in Scientific Article No.1 give a sound indication (status quo) of the condition during the period of report vis-à-vis the thermal comfort (or rather the lack of it) in five naturally ventilated RBs in Malta when contrasted to EN 16798-1 Category 3. Though for Baroque Churches, both design and typical weeks in summer generally recorded temperatures within the comfort limits, the application of mechanical cooling was still being sought. This anomaly prompted further investigation and a Qualitative Analysis of worshipers’ and pastors’ perception of indoor comfort, by means of questionnaires, was conducted. The outcome of this qualitative research is portrayed in Scientific Article No.2. 66 Figure 30 - Balzan – The Annunciation Parish Church – EN 16798-1 Category 3 Comfort Analysis Figure 14: Balzan – The Annunciation Parish Church - EN 16798-1 Category 3 Comfort Analysis \\\ 67 Figure 31: Stella Maris Parish Church – EN 16798-1 Category 3 Comfort Analysis. Figure 15: Sliema - Stella Maris Parish Church - EN 16798-1 Category 3 Comfort Analysis 68 Figure 32 - Msida – St. Joseph Parish Church – EN 16798-1 Category 3 Comfort Analysis Figure 16: Msida – St. Joseph Parish Church - EN 16798-1 Category 3 Comfort Analysis 69 Figure 33 - Santa Venera – Santa Venera Parish Church – EN 16798-1 Category 3 Comfort Analysis Figure 17: Santa Venera – Santa Venera Parish Church - EN 16798-1 Category 3 Comfort Analysis 70 Figure 18: Fgura – Our Lady of Mount Carmel Parish Church - EN 16798-1 Category 3 Comfort Analysis Figure 34 - Fgura – Our Lady of Mount Carmel Parish Church – EN 16798-1 Category 3 Comfort Analysis. 77 churches are deemed thermally comfortable according to both the EN standard and data gathered through questionnaires, the installation of ACs in baroque churches became even more questionable and the implementation of passive measures pronounced. 3.4 Scientific Article No. 3 Using DesignBuilder-EnergyPlus software, Scientific Article No. 3 Prioritising Passive Measures over Air Conditioning to Achieve Thermal Comfort in Mediterranean Baroque Churches, investigates the efficacy of selected passive measures in two free-running church buildings, namely that of Stella Maris Parish Church in Sliema and Our Lady of Mount Carmel Parish Church in Fgura. The major goal in this paper was to determine whether the implementation of passive design practices would improve the interior thermal comfort, whilst preventing the use of mechanical cooling, thus minimizing the energy consumption, and reduce carbon emissions. For this study, the interpretation of the interior thermal comfort was measured in accordance with the same adaptive comfort model (EN 16798-1 standard) using the category 3 comfort limits. The quantification of such improvement in thermal comfort, if any, was determined through the reduction in the number of discomfort days. Moreover, the on-site data was also gathered through the continuation of the indoor and outdoor monitorisation of air temperature and relative humidity using the HOBO data loggers. In order to assess the effect of the passive measures on the thermal comfort within the church buildings under study, a software simulation approach was adopted. The Designbuilder was the model of choice for this case. This software, which is an advanced user interface to Energy Plus, is a standard building modelling tool that gives access to all of the most frequently used simulation functions, including those for renewable energy sources, building fabric, thermal mass, glazing, and shading. Respective church building models were generated within this software and supplied with identical building envelope characterisation properties, occupancy schedules, and lighting fixtures to attain an accurate indoor environment of the true scenario. Both software models underwent a validation process to access whether the 78 latter was attained. This was conducted by comparing the annual simulated indoor air temperature data with that measured for the particular year of the monitorisation period. In this case it was repeated for three consecutive years (2018, 2019 and 2020). In addition, the compiled weather files for the respective years were inputted in the software to enable an accurate comparison between the measured data and the simulated model for each year under consideration. The weather files were compiled using weather data from the Meteorological Office of the Malta International Airport (MIA) and solar radiation data from the Institute for Sustainable Energy of the University of Malta. The year 2019 was the optimal year providing the lowest margin of acceptable discrepancy between modelled data and actual temperatures monitored within the churches. In this study, software modelling was used to simulate the summer design week, the summer typical week, the winter design week, and the winter typical week in 2019 for both churches under review. The design and typical weeks were automatically generated through the EnergyPlus configuration of data analysis. In this investigation, two passive measures gave rewarding results. The first was a 3mm coating of liquid white acrylic polymer paint applied to the roof, and the second was a layer of "EPS extruded polystyrene (standard)" applied in thicknesses of 5 and 10cm. Each passive measure was simulated individually to allow for comparison and evaluation of their own effectiveness and performance. Additionally, the relationship between the simulated indoor air temperature with and without PM in relation to the EN16798-1 category III comfort limits was established in each case using the adaptive comfort model, to evaluate and determine the level of comfort. The application of the white acrylic polymer paint on the roofs proved to alleviate the indoor temperatures in both churches under study (refer to Figures 38 and 39), with its effectiveness being more pronounced during the summer period. This is attributed to the decrease in the solar absorbance at the roof surface. The application of the EPS proved to be superior to the white acrylic polymer paint in terms of enhanced indoor comfort for the Sliema parish church. This is manifested through further decreased indoor temperatures during the summer period whilst also attaining higher indoor temperatures during the winter period thus exhibiting its beneficial performance not just for the summer period but throughout the full year. Results also established that the thickness 79 of EPS application and the indoor temperature are not directly proportional with 50% increase in the EPS thickness exhibiting only a minor decrease in the indoor temperature. On the other hand, the white acrylic polymer paint proved to be superior to the EPS application for the Fgura parish church. This is attributed to the fact that the church, apart from having a low thermal mass, has a high percentage of glazing. This study demonstrates that historic church buildings defeat expectations and, in general, outperform more modern church buildings. Historic church buildings were originally constructed to make advantage of passive design characteristics for internal comfort. In conclusion, as seen in Figures 38 to 41, data indicate that passive measures reduce extreme hot and low interior temperatures, creating a more pleasant environment. 80 Figure 38 - Sliema Simulated Indoor Temperature including 3mm White Acrylic Polymer Paint (Occupied Hours). 20 22 24 26 28 30 32 34 36 38 40 Sat Sun Mon Tue Wed Thu Fri Sat Temperature °C Date (July 06 - 12) Summer Design Week 20 22 24 26 28 30 32 34 36 38 Sat Sun Mon Tue Wed Thu Fri Sat Temperature °C Date (June 08 - 14) Summer Typical Week 5 7 9 11 13 15 17 19 21 23 25 27 29 Sun Mon Tue Wed Thu Fri Sat Sun Temperature °C Date (December 22 - 28) Winter Design Week ● Outdoor Temperature, °C ♦ Simulated Indoor Temperature, °C ■ Simulated Indoor Temperature, °C (3mm Acrylic Polymer) ⁃ Upper Comfort Limit (EN 16798-1) ⁃ Lower Comfort Limit (EN 16798-1) 5 7 9 11 13 15 17 19 21 23 25 27 29 Sun Mon Tue Wed Thu Fri Sat Sun Temperature °C Date (January 27 - February 02) Winter Typical Week 81 20 22 24 26 28 30 32 34 36 38 40 Sat Sun Mon Tue Wed Thu Fri Sat Temperature °C Date (July 06 - 12) Summer Design Week 20 22 24 26 28 30 32 34 36 38 Sat Sun Mon Tue Wed Thu Fri Sat Temperature °C Date (June 08 - 14) Summer Typical Week 5 7 9 11 13 15 17 19 21 23 25 27 29 Sun Mon Tue Wed Thu Fri Sat Sun Temperature °C Date (December 22 - 28) Winter Design Week ● Outdoor Temperature, °C ♦ Simulated Indoor Temperature, °C ■ Simulated Indoor Temperature, °C (3mm Acrylic Polymer) ⁃ Upper Comfort Limit (EN 16798-1) ⁃ Lower Comfort Limit (EN 16798-1) 5 7 9 11 13 15 17 19 21 23 25 27 29 Sun Mon Tue Wed Thu Fri Sat Sun Temperature °C Date (January 027 - February 02) Winter Typical Week Figure 39: Fgura Simulated Indoor Temperature including 3mm White Acrylic Polymer Paint (Occupied Hours). 82 ● Outdoor Temperature, °C ♦ Simulated Indoor Temperature, °C ■ Simulated Indoor Temperature, °C (5cm EPS) ● Simulated Indoor Temperature, °C (10cm EPS) ⁃ Upper Comfort Limit (EN 16798-1) ⁃ Lower Comfort Limit (EN 16798-1) Figure 40 - Sliema Simulated Indoor Temperature including 5cm/10cm EPS Extruded Polystyrene (Occupied Hours) 83 20 22 24 26 28 30 32 34 36 38 Sat Sun Mon Tue Wed Thu Fri Sat Temperature °C Date (June 08 - 14) Summer Typical Week 20 22 24 26 28 30 32 34 36 38 40 Sat Sun Mon Tue Wed Thu Fri Sat Temperature °C Date (July 06 - 12) Summer Design Week 5 7 9 11 13 15 17 19 21 23 25 27 29 Sun Mon Tue Wed Thu Fri Sat Sun Temperature °C Date (December 22 - 28) Winter Design Week 5 7 9 11 13 15 17 19 21 23 25 27 29 Sun Mon Tue Wed Thu Fri Sat Sun Temperature °C Date (January 027 - February 02) Winter Typical Week ● Outdoor Temperature, °C ♦ Simulated Indoor Temperature, °C ■ Simulated Indoor Temperature, °C (5cm EPS) ● Simulated Indoor Temperature, °C (10cm EPS) ⁃ Upper Comfort Limit (EN 16798-1) ⁃ Lower Comfort Limit (EN 16798-1) Figure 41 - Fgura Simulated Indoor Temperature including 5cm/10cm EPS Extruded Polystyrene (Occupied Hours) 84 CHAPTER 4: CONCLUSION AND FUTURE WORKS 4.1 Conclusion This information provides further assurance to decision-making bodies in addressing carbon neutrality by 2050. This is in line with the 2030 National Energy and Climate Plan (NECP) which aims to achieve a sustainable infrastructure in favour of climate change abatement and mitigation. The thermal comfort demand for users in church buildings has increased exponentially over the past years and this was erroneously mitigated by quick solutions such as the introduction of heating and cooling systems, which could have detrimental effects on valuable artefacts such as paintings, frescoes and prestigious ornaments found within these buildings. Thus, prioritising passive measures as opposed to the conventional mechanical airconditioning systems within such buildings is an important step towards safeguarding the macroclimate, whilst attaining a sustainable and comfortable indoor environment. In conclusion, this research addressed the projected key questions in three scientific articles as follows: Paper 1: To what extent are places of worship both traditionally and newly built conforming to indoor comfort levels in accordance with the EN16798-1 standard? Paper 2: How do communities frequenting places of worship relate to the indoor comfort conditions for different seasons? Paper 3: To what extent do passive building envelope measures and their prioritisation contribute towards improving the indoor building environment in places of worship and therefore avoiding the installation of mechanical air-conditioning systems? This research highlights that modification of the indoor climate, with both passive and active measures, present complex conservation issues, and the understanding of the local limestone matrix, texture, and porosity, is imperative for informative decisions. Measures to prevent the highly fluctuating external climates alone from impacting the indoor climate is not 85 necessarily a solution to address indoor comfort. Subjecting the building fabric and indoor climate to changes may give rise to unpredicted complications. This study shows that historic church structures outperform expectations than more modern church buildings. Historic church buildings were initially constructed to make use of passive design techniques for internal comfort. The local architectural typology was created through many years of practice with the intention of giving building inhabitants a comfortable interior space. Therefore, the heritage building typology provides enormous possibilities for lowering energy consumption, maintaining balanced environmental conditions for artifacts, and meeting occupant comfort standards. Despite this, there is a perception that churches do not offer comfortable interior environments for building occupants, and a new trend has emerged where the criteria to improve thermal comfort have been restricted to a paper exercise to determine what size air conditioner is necessary to address the cooling capacity. This, to the detriment of needless retrofits that impair the historic building's structural integrity and adorned artefacts. This study further highlights the present situation whereby when faced with the decision of implementing passive energy-efficient measures, nature is viewed as secondary while the installation of ACs is viewed as essential. Attempts to promote thermal comfort primarily by cooling within inhabited buildings while achieving acceptable quality energy efficiency have been a key challenge on an island located within a Mediterranean environment, with scorching temperatures dominating much of the year. This study shows that considering passive measures in free-running buildings give advantageous results. It is not appropriate to prioritise occupant thermal comfort within historical and prestigious buildings using un-justified mechanical systems at the expense of jeopardising the integrity of the artefacts historical value. Though it is becoming the norm to overlook low-cost, low-energy, passive solutions for naturally ventilated structures in the pursuit of a single technical solution, this is not sustainable. The findings of this study demonstrate that passive measures may be used in churches, even though each church in Malta has distinct and unique issues. In summary: ▪ Implementing solar control techniques, such as painting roof surfaces with white solar-reflective paint to achieve a ‘cool roof’, can greatly reduce heat discomfort. 86 ▪ Roof thermal insulation greatly enhances both indoor comfort and thermal performance. ▪ The use of certain PM is restricted by the architectural aesthetical values of heritage structures. ▪ Owing to PM, the heritage building typology has the capacity to preserve balanced indoor environmental conditions for artifacts and meet occupant comfort criteria. ▪ One can analyse the influence of phased exclusion of external climates and the proper humidity and temperature values required to address human comfort with a detailed understanding of local building construction techniques and building block characteristics. Policymakers, architects, and engineers now have a greater understanding of how to put passive conservation techniques into practice that may be useful for their preventative conservation without compromising human comfort. As a result, one must promote passive control systems and, on a case-by-case basis, make the required modifications to increase Indoor Thermal Comfort. The findings of this study are in line with the objectives proposed by the European Parliament, the Council and the European Commission in the ‘Conference on the Future of Europe’, in order to provide sufficient, affordable and sustainable energy [116]. It is obvious to everyone that the goals of the 2015 Paris Climate Summit cannot be achieved without significant and urgent changes in our way of life. 4.2 Future Works Experts are warning that nowhere near enough is being done to ventilate public and private spaces across the world. 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Clark, Long distance airborne transmission of SARS-CoV-2: rapid systematic review, BMJ. 377 (2022) e068743. https://doi.org/10.1136/BMJ-2021-068743. 97 APPENDICES APPENDIX A - Complementary Paper ‘Monitoring Indoor Temperatures of Places of Worship: A First Step Towards Energy Sustainability Engineering Sustainability and Sustainable Energy’; (ESSE ’18) Conference organised by the Chamber of Engineers in collaboration with the Institute for Sustainable Energy of the University of Malta, St. Paul’s Bay, 8 May 2018, pp. 55-66, ISBN: 978-99957-853-2-1, https://www.um.edu.mt/library/oar/handle/123456789/30540 110 APPENDIX B - Scientific Article No. 1 ‘A study of thermal comfort in naturally ventilated churches in a Mediterranean climate’; published by Energy & Buildings Journal, Volume 213, 2020, 109843, ISSN 0378-7788, https://doi.org/10.1016/j.enbuild.2020.109843 133 APPENDIX C - Scientific Article No. 2 ‘Thermal Comfort in Places of Worship within a Mediterranean Climate’; published by Sustainability Journal 2021, 13, 7233, https://doi.org/10.3390/su13137233 160 APPENDIX D - Scientific Article No. 3 ‘Prioritising Passive Measures over Air Conditioning to Achieve Thermal Comfort in Mediterranean Baroque Churches” published by Sustainability Journal 2022, 14(14), 8261 https://doi.org/10.3390/su14148261 184 APPENDIX E - UV IV Conference Certificate Certificate from the Coordinator of the Doctoral Program in Industrial Engineering from the University of Valladolid on successfully accomplishing IV Conference of Doctoral Students PD Industrial Engineering organized by the Academic Committee of the Doctoral Program in Industrial Engineering of the University of Valladolid, on 14 September 2017. 185