Thermo-hygrometric Conditions Research Articles

A Multidisciplinary Approach to the Evaluation of Air Quality and Thermo-Hygrometric Conditions for the Conservation of Heritage Manuscripts and Printed Materials in Historic Buildings: A Case Study of the Sala del Dottorato of the University of Perugia as a Model for Heritage Preservation and Occupants’ Comfort

The Sala del Dottorato (Hall of Graduates) is a magnificent library in the University of Perugia which plays the double role of providing optimal conservation of valuable books and manuscripts while also hosting important events. This double role is closely connected to contrasting indoor microclimatic conditions. This paper presents the results of a multidisciplinary study, begun in 2019, which investigates optimal conditions for the conservation of volumes by monitoring thermo-hygrometric and air quality parameters. The study describes the current conditions of the Hall (in terms of air temperature, relative humidity and concentration of CO2), highlighting critical aspects, defining strategies for their mitigation and control, and outlining future developments. Improvement measures relate to the installation of a permanent monitoring system with alarm settings and data storage, technical interventions on the windows, and the restoration of several volumes. The paper shows the importance of monitoring as an instrument of control in real time and provides guidelines for management to be implemented according to indoor microclimatic conditions.

Modeling of Indirect Evaporative Cooling Systems: A Review

Air-to-air indirect evaporative cooling (IEC) systems are particular heat exchangers that use the latent heat of evaporation of water to cool down an air stream, without increasing its specific humidity, thus guaranteeing adequate thermohygrometric conditions in the refrigerated environment with low energy consumption. Dew-point indirect evaporative cooling (DIEC) systems are based on the IEC technology, but they recirculate a part of the air taken from the room to be refrigerated, in order to possibly achieve a lower air temperature. IEC and DIEC systems are becoming increasingly common these years, as they can ensure a good efficiency, minimizing the environmental impact of the air-conditioning system. Consequently, it has been necessary to develop models, both analytical and numerical, to quickly and accurately design this type of system and to predict their performance. This paper presents a review of the analytical and numerical models developed specifically for IEC and DIEC systems, highlighting their method, main innovations and advantages, and possible limitations. From this analysis, it emerged that analytical models have been developed since the late 1990s and only few of them are suitable for DIEC heat exchangers, while numerical models for both IEC and DIEC systems are gaining popularity in recent years. Almost all the analyzed models have been validated by comparison with numerical and/or experimental data, showing a maximum discrepancy within 10% in the majority of the cases. However, the validations were performed for a few specific cases, so in real applications it might be difficult to associate the model boundary conditions and the heat exchangers operating conditions, such as nozzles orientations, plates materials, water flow rates, and configurations. Another common limitation concerns the modeling of some properties, as wettability factor and air density, which might affect the accuracy of the results.

The influence of thermo-hygrometric conditions on metamaterials' acoustic performance: an investigation on a 3D printed coiled-up resonator

In the last decades, coiled-up resonators have become popular within the metamaterial research community for narrow band, low frequency resonances combined to subwavelength thickness. Such structures are particularly suited to one of the most widespread manufacturing processes, i.e. PET-based 3D printing. Acoustic performance of coiled-up resonators depends on the geometrical parameters' variation, which is influenced by thermo-hygrometric conditions; however, the deformation itself needs to be further investigated. For this reason, the present paper evaluates the correlation between temperature, relative humidity, and the geometrical parameters' (spiral length and hole diameter) deformations and, consequently, the acoustic performance of a 3D printed coiled-up resonator. A combined approach through analytical, numerical, and experimental measurements quantified the frequency shift of the resonance peaks (within 300 Hz - 5000 Hz) in terms of sound absorption coefficient increasing the temperature (T=10-50° C), and the relative humidity (RH=20-80 %) of the samples. Relative humidity variations turned neglectable discrepancies on sound absorption's peaks. On the other hand, the increase in temperature caused a frequency peaks' shift following an exponential trend: this behavior is straight related to the exponential relationship between the temperature and specific volume function of polyethylene resins.

Assessment of fungal aerosols in a public library with natural ventilation

Fungal aerosols deteriorate library collections and can impact human health, mainly via respiratory diseases. Their spread is influenced by factors such as temperature and relative humidity. This study aims to assess the concentration of fungal aerosols in the interior environment of the Popular Library of Gaira in the District of Santa Marta, Colombia, using a two-stage cascade impactor utilizing Sabouraud dextrose agar on Petri dishes for the collection of samples. The sampler was positioned at 1.5 m above ground level, operated with a flow rate of 28.3 l/min for 4 min and thermo-hygrometric conditions were also recorded. Concentrations in the air of up to 1197.0 CFU/m3 were reported, with a mean value close to 150 CFU/m3. Higher values during the morning samples were noted. Seven genera of fungi were found, Aspergillus and Curvularia were the most abundant. The temperature was between 30.80 and 33.51 °C, and the relative humidity was between 62.61 and 64.80%. Statistical analysis showed a significant correlation between the fungal aerosol concentration and relative humidity, where an increase of 10% in moisture could double the fungal aerosol concentration. We concluded that potentially favorable conditions exist indoors for the growth and survival of the following fungi: Aspergillus, Penicillium, Cladosporium, and Curvularia, and to a lesser extent for Chrysonilia, Cunninghamella, and Paecylomices. Relative humidity was seen to be the factor that affects the concentration of aerosols fungal in the library most significantly.

Impact of Temperature and Relative Humidity on Reverberation Time in a Reverberation Room

Changes in acoustic parameters measured in a room may depend on the location and orientation of the sound source and microphones or on the reverberation conditions of the room. As was found in the research presented in this publication, reverberation in a room is also influenced by thermo-hygrometric conditions. The article presents an experimental analysis involving the impact of temperature and relative air humidity in a room on reverberation time. Since it is very difficult to control the temperature and relative humidity in real conditions, the tests were carried out both in laboratory conditions and with the use of simulations. For this purpose, the results of the reverberation time measurements in the reverberation chamber for various thermo-hygrometric conditions were obtained. Then, the reverberation chamber was modeled in the ODEON Version 11.0 program, and after the validation of the model, a series of simulations were performed, demonstrating the changes in the reverberation time as a function of temperature and relative air humidity. The results are presented in both a two-dimensional and three-dimensional version, i.e., the dependence of the reverberation time as a function of two variables: air temperature and relative humidity.

A Preliminary Study of Summer Thermo-Hygrometric Comfort under Different Environmental Conditions in a Mediterranean City

The thermo-hygrometric sensation of pedestrians in outdoor environments can be quantified by means of bioclimatic indices. In this work, the Mediterranean Outdoor Thermal Comfort Index (MOCI) is applied in the city of Rome (Italy) for the purpose of investigating the effect of local environmental conditions (urban, suburban, rural) on pedestrian thermal comfort. Hourly values of MOCI are calculated for the May–September period in the years 2015–2021 using weather quantities acquired by the four monitoring stations of the Regional Agency for Environmental Protection included in the metropolitan area of Rome. MOCI data are analyzed based on the comfort and (cold/hot) discomfort conditions during both daytime and nighttime. At the urban station, 26% of daily records exceed the comfort threshold revealing the effect of urban overheating, whereas only 0.1% of hot discomfort occurrences are recorded overnight. Here, greater nighttime thermal comfort is experienced than in non-urban locations suggesting that the nocturnal thermo-hygrometric conditions are satisfactory for inhabitants in downtown Rome, despite the urban heat island. It also suggests that other factors, such as orography and atmospheric circulation, influence outdoor thermal comfort. The development of this work will therefore include at least these two elements.

Effects of operating room layout and ventilation system on ultrafine particle transport and deposition

The main role of Heat Ventilation and Air Conditioning (HVAC) systems in Operating Rooms (ORs) is to ensure the desired thermo-hygrometric conditions and indoor air quality, minimizing the risk of air contamination. The main sources of contamination inside ORs, during surgical operations, are Colony-Forming Units (CFUs), fine particles and ultrafine particles (UFPs), which could cause surgical site infections or health issues for the medical staff. The present work aims at increasing the scientific knowledge concerning numerical modelling of the UFP transport and deposition in ORs, analysing the effectiveness of three different ventilation systems. A numerical methodology, validated in previous works, has been used to study UFP transport and deposition inside three actual ORs, two of them equipped with a Laminar AirFlow (LAF) system and one with a Turbulent Mixing Airflow (TMA) system. Both the LAF and the TMA systems effectively evacuate the UFPs, ensuring a particle deposition rate significantly lower than the evacuation rate. The installation of extraction grilles near the surgical table allows obtaining an improvement of UFP evacuation. Due to the not perfect symmetry of OR layouts and surgical wound position, a preferred way for UFP transport can be observed. The instrument table position should be chosen consequently, to reduce UFP, CFU and contaminant deposition. The UFP concentrations at surgical staff head height cannot be neglected for health-related risks.

Spanish Royal glasses with crizzling in historical buildings. The importance of environmental monitoring for their conservation

Crizzling is an alteration pathology of non-equilibrated glasses that can produce a fast surface alteration. The Royal Palace of Madrid and the Technological Museum of Glass (Segovia) preserved pieces with incipient crizzling produced by the Spanish Royal Glass Factory in the first decades of the 19th century. The objective of this study was to assess the environmental conditions in both collections to enhance their preservation conditions and to identify possible pollutants that can accelerate their alteration. Both collections presented suitable thermohygrometric conditions for general collection; however, it was observed that illumination induces humidity fluctuations inside the cabinets. Passive samplers detected a high concentration of formic acid in some locations, mainly related to the presence of wood furniture. In these locations, glass pieces showed a high surface hygroscopicity (pH 8) and a high concentration of K+- and COOH− ions.

Analysis of the state of conservation of historical plasterwork through visual inspection and non-destructive tests. The case of the upper frieze of the Toledanos Room (The Royal Alcázar of Seville, Spain)

State of conservation studies carried out before rehabilitation and restoration interventions constitute solid support to make decisions about architectural heritage. In this way, the study of historical plasterwork has been performed through non-destructive tests by measuring environmental conditions and surface properties, taking thermographic images, mapping risks by indicating cavities, cracks and metal fixings -among others- and checking the stability of the present polychrome.This method was applied in the plasterwork of the upper frieze of the Toledanos Room, in the Royal Alcázar of Seville, due to the relevance of the building and its decorative coatings, and established parameters to assess the state of conservation of both, the Royal Alcázar of Seville plasterwork and other heritage buildings with similar coatings.The compilation and analysis of all the results presented in this paper show a positive assessment of the stability and conservation of the frieze plasterwork. Thermohygrometric conditions and physical-mechanical properties are acceptable, vertical cracks – sometimes of large dimensions and also great depth-are stabilized and apparently do not affect the structural integrity and polychromies studied are mostly unstable and re-chromatics were widely used in previously inpainting to imitate reliefs inadequately.

Evaluation of the heat changes in an ancient church because of restoration works: A microclimatic study supported by thermal images

This work is centred on an ancient Italian church. Since 2011, a restoration plan has been undertaken by following sequential phases. The methodological approach to restoration was guided by environmental monitoring campaigns. In particular, two thermo-hygrometric campaigns were carried out during the warm months of the years 2015 and 2016. The first set of measurements was executed during the restoration of facades and roofs, making it possible to reach even areas that are usually difficult to access. The second set was performed to evaluate the indoor thermo-hygrometric conditions following the work of the previous year. This was intended to assess their differences in variability, the influence of the outdoor environment and any real and perceived improvement. Results demonstrate that thermal images helped in identifying both the heat sources causing thermal discomforts and the good thermal capacity of masonries. Concerning the heat index (HI), the church showed an improvement in the trend of malaise perceived by people during the second summer period (∼2°C lower than 2015). Finally, in the last microclimate monitoring, the roof structure no longer acted as an amplifier for daily temperature excursions.

An AI-based DSS for preventive conservation of museum collections in historic buildings

The study deals with the experimentation of innovative and advanced preservation methodologies for museum collections in historical buildings. In particular, this work shows the development of an algorithm, based on Machine Learning techniques, that suggests which actions to undertake in relation to thermo-hygrometric conditions. The aim is to guarantee microclimate conditions that are favorable both for collections and architecture.In order to boost the time required to gather the needed dataset a possibility is to train the decision-making model based on machine learning through the use of a synthetic dataset created via plugins connected to VPL (Visual Programming Languages) that allow the simulation of different scenarios starting from open source data. The training of the machine learning mechanism will be supervised and each solution will be “an experience” for the building from which to learn. Along the time thanks to experience and background data the decision-making system will improve the quality of his work.

Pontes térmicas em estruturas de concreto

A importância de considerar as pontes térmicas e seus impactos no cálculo de transmitância térmica é um assunto que tem sido discutido em regiões de clima com estação fria no Brasil. A presença de pontos vulneráveis no envelope do edifício pode ter consequências no desempenho térmico, além das implicações nas paredes e coberturas do edifício, como por exemplo a formação de fungos filamentosos. Várias normas e regulamentos tratam da temática. Esse estudo tem por objetivo discutir, por intermédio de simulação computacional, a necessidade das normas Brasileiras de desempenho considerarem a possibilidade de formação de fungos filamentosos nas edificações com baixo e elevado isolamento térmico. Na análise examina-se as condições termo-higrométricas próximas a estrutura de concreto armado do modelo da edificação onde ocorrem as pontes térmicas, e as superfícies dos fechamentos vertical, de alvenaria, para todas as fachadas. Os resultados mostram que existe uma elevada probabilidade de crescimento dos fungos filamentosos nas pontes térmicas quando o edifício é mais isolado, ou seja, apresenta baixa transmitância térmica.

Towards IoT monitoring of street-side monuments: the Florentine Dietrofront as a case study

The need for care often shown by ageing cultural heritage and the circumstantial lack of dedicated budget are increasingly calling for smart monitoring solutions to shift the maintenance paradigm from reactive-preventive to predictive. Monitoring artworks poses additional issues with respect to the more common industrial solutions, such as aesthetics, dealing with unusual materials, remote locations (archaeology), etc. In this scope, the “Dietrofront” statue in Florence, by artist Michelangelo Pistoletto, is an emblematic instance. Installed on a traffic roundabout, it comprises four travertine blocks, one of which hangs 5 m above the ground supported by a steel structure which has shown relevant symptoms of damage during the 2006 restoration works. During a later intervention, we seized the opportunity to equip the structure with a three IoT sensing devices, so as to monitor thermo-hygrometric conditions, inclination and vibrations of the structure. Various issues common to outdoor monuments have been faced, such as the need for visual non-intrusiveness and the unavailability of power supply. A small wireless sensor network was designed and installed, also exploiting an existing room inside the nearby mediaeval city gate. The network is fully solar-powered by photo-voltaic modules integrated on both the statue and the gate and not visible from the street. The data obtained have been analysed and compared to a simple lumped-parameters structural model, so as to estimate the relevance of traffic-induced vibration on the steel structure. The risk of water vapour condensation has also been assessed.

Assessing the Indoor Conditions of a 3rd Century AD Roman Domus by Dynamic Energy Simulation and Comparison with Vitruvian Hypothesis: Preliminary Findings

Roman best practices concerning construction technology were well consolidated and implemented in ancient times. These are traditionally belonging to Vitruvius, who coded the classic rules on architecture. Amongst these, the destination of use of the different rooms is paramount, especially in respect to the orientation of the building. Dynamic energy simulation software is a tool of proven effectiveness and of widespread diffusion in the field of building engineering. It is primarily used to evaluate and foreseen the effects that building stratigraphy, thermal loads and HVAC systems have on the indoor thermo-hygrometric conditions. In this study, such tool has been used to investigate ancient buildings, basing the analysis on reliable hypothesis about the original construction, partially assumed if the upper structures were missing, on the actual stratigraphy obtained from archaeological remains, and on the supposed ancient climate condition estimated from literature on ancient climate and archaeological evidences. The analyzed case study is a Roman domus that dates back to 3rd century AD, located in Piazza Nogara (Verona, Italy). The proposed method allows evaluating the indoor comfort conditions that occurred when the building was inhabited. Furthermore, simulating different building orientations, it is possible to verify if the actual destination of use of the rooms is the very best from an indoor microclimate standpoint.

On the interaction between lighting and thermal comfort: An integrated approach to IEQ

A sustainable building design should be compliant with the even more pressing energy saving requirements – as in NZEB – and high levels of Indoor Environmental Quality. Despite it is accepted that different facets of IEQ could have antagonistic effects on building energy demand, relatively few studies are aimed at investigating the mutual interaction among its four components. From this point of view, the hue-heat hypothesis is based on the idea that light and colors can affect the thermal perception. Particularly, spectral power distributions of light shifted to short wavelengths seem to promote a cooler thermal perception and vice-versa. To verify this still debated hypothesis, this paper is focused on a subjective investigation carried out in a special mechanically conditioned test room provided with white-tuning LED sources. 163 volunteers have been exposed to two different lighting scenarios characterized by warm (3000 K) and cool lights (6000 K) at a fixed work-plane illuminance value (300 lx) at two different operative temperature values (20 °C and 25 °C). Obtained results seem to confirm that warm light results in a warmer thermal sensation. Probably due to thermohygrometric conditions relatively close to comfort, no effects on thermal evaluation, and thermal preference were found under both microclimatic scenarios. This was also about the effects of CCT on humidity perception and game performances.

Accelerate ageing on building stone materials by simulating daily, seasonal thermo-hygrometric conditions and solar radiation of Csa Mediterranean climate

The maintenance plan of ancient and contemporary buildings today takes on strategic importance and should include the identification of climatic environment where the structures are located. Researcher are trying to evaluate the response to weathering of the building materials by accelerated ageing tests. This technique often consists of the “aggravations practice”, by subjecting materials to extreme climate parameters not representative of the real environment conditions. For this reason, this type of ageing presents a lot of criticisms. This research addresses the lacking of literature about the realistic simulation of a determinate environment/climate on building stone materials. The aim of this research is to understand if it is possible to recreate in laboratory the pathologies observed on building stones of ancient monuments from Sardinia (Italy) by simulating the climatic context of location. To do so, samples were undergone to accelerated cycles of thermo-hygrometric conditions and solar radiation for simulating realistic parameters of Csa Mediterranean climate. Monitoring of some physical/mechanical properties before and after ageing indicates an overall decohesion of samples, the appearance of decay patinas and a slight worsening of mechanical resistances. A mathematical equation relates the ageing test duration (6 months) with the hypothetical outdoor exposure quantifiable in ≈18 years for samples evolved to temperature and humidity cycles while ≈3.7 years for the samples subjected to only solar radiation. However, the test should to be reproduced in the natural outdoor environment to correlate and verify the reliability of the obtained data (test the test).

Outdoor thermal perception and comfort conditions in the Köppen-Geiger climate category BSk. One-year field survey and measurement campaign in Konya, Turkey

This study presents an analysis of the thermo-hygrometric conditions in the city of Konya (Turkey). A one-year transversal field survey was carried out in the Selçuk University campus and 2295 valid questionnaires were collected. In each questionnaire, randomly selected interviewees provided personal information and judged their perception and thermal preference according to the ASHRAE 7-point and McIntyre scales, respectively. For each interviewee, a value of the Physiological Equivalent Temperature (PET) was calculated based on the values of operational variables obtained from the questionnaires and the environmental variables measured during the survey. This allowed to calculate the seasonal preferred and neutral PETs and the annual PET comfort range. Also, the scale of the PET thermal perception was determined for the Konya population and, more generally, for the inhabitants of the BSk Köppen-Geiger climate zone. Statistical analyzes carried out in terms of Variance Inflationary Factor, multicollinearity assessment and Best Subsets Analysis led to the identification of the Turkish Outdoor Comfort Index, an empirical index able to predict the average value of the thermal perception of a large group of individuals living in the aforementioned climate zone. Moreover, the equations of the Predicted Percentage of Dissatisfied (PPD) were obtained for each season.

Application of basket geothermal heat exchangers for sustainable greenhouse cultivation

The residential building sector is recently experiencing a large reduction of energy demand for conditioning, nevertheless, the use of energy in agro-industrial productions is constantly growing and the research of alternative and more sustainable sources has become necessary. In the greenhouses production, the energy problem is relevant since high demand is required, even for long periods with considerable peak requests and the use of renewable energy sources in such productions can allow a significant reduction of fossil fuel consumptions, greenhouse gas emissions and running costs.In this context, this paper analyses the performance of a low-enthalpy geothermal system, consisting of basket geothermal heat exchangers with a ground source heat pump, specifically studied to provide the base load for winter heating demand of a greenhouse. Due to the large thermal demand requested by the greenhouse, the existent pressurized gas boiler and two existent air source heat pumps, now also converted to work in heating mode, cover the remnant demand. Based on the thermo-hygrometric data, collected during an experimental campaign carried out on a case study farm, the study evaluates the performance of the geothermal system prescribing the optimal thermo-hygrometric conditions requested for the production of three different protected crops. The shallow geothermal field operates mainly during the night-time, allowing the thermal recover of the ground during the daytime. The results provide an assessment of the performances of the hybrid system in terms of primary energy needs, running costs and CO2 with respect to the existent system.

Improvement of a functional method to determine the design thermal transmittance of building façades. Implementation in southern Spain

The thermo-hygrometric conditions to which construction materials are subjected cause their thermal performance to vary by location. These variations must be characterised in order to design building envelopes adjusted to the requirements of each situation, thus contributing to improve their energy efficiency under actual operating conditions. To this end, a functional calculation procedure that corrects the standardised thermal conductivity values of façade materials (λ-value) has been recently proposed; which considers the climatic characteristics of each location. This work proposes and validates improvements that, while preserving its functionality, overcome some limitations of the original procedure. To calculate more accurate corrections, the façade configuration and the climatic zones established by the building codes are also considered, allowing a more reliable characterisation of the design thermal transmittance of each building façade. By using climatic records gathered from 316 weather stations, a detailed isopleth map is also developed to present the applicable corrections for more than 250,000 km2 of southern Spain. The largest λ-value corrections are identified on the southeast coast and reach up to +6% in the summer months (with average annual corrections above +4%). This improved procedure can be extrapolated to any national building code that establishes constant values of thermal conductivity for façade materials and that defines thermal design requirements based on climatic zones.

An OpenFOAM simulation of the natural ventilation system in a university chemical laboratory

The indoor airflow with a natural ventilation system was numerically calculated using the laminar and turbulent approach. In the chemical laboratory of the Technical University of Ambato, the computational code OpenFoam demonstrated an ability to numerically predict flow patterns. The design contemplated the natural ventilation system considering the laboratories’ working conditions not only in summer, but also in a winter week. These two operating conditions are calculated on a fully open and closed environment. For a room with a capacity of 20 people, the climate data average values were recorded at 14.0 ° C, 81.7%, 1.7 m /s for temperature, relative humidity, and wind speed, respectively. Furthermore, the demonstration has shown that the homogeneous occupancy air speed average is was 0.7 m / s with a facade air intake of 1.0 m / s 0.6 m / s in the room valid for the exchange of air and evacuation of pollutants. The maximum pressures were found in the lower part of the laboratory. This prevents the modification of the thermo-hygrometric conditions.