Indoor Air Temperature Research Articles

Integrating vertical greenery for complex building patterns towards sustainable urban environment

Rapid urbanization has increased the urban density and functional diversity, exacerbating environmental challenges such as urban heat islands (UHI), increased building energy consumption and carbon emissions, etc., hindering the sustainable urban development. Addressing these challenges requires innovative solutions that could offer the strategic cooling of urban buildings. Vertical greenery, affixed to building façades, offers a promising approach to provide benefits of cooling, energy savings, carbon reduction and urban space saving. However, there is a lack of quantitative design for integrating vertical greenery into complex urban buildings. Therefore, this study conducts a systematic investigation for low-rise, mid-rise, and high-rise buildings incorporating vertical greenery, while performing comprehensive assessments on indoor and outdoor thermal conditions, building energy usage, and carbon emissions. The findings suggest that low-rise buildings benefit from a vertical greenery layout, while mid-rise and high-rise buildings are better suited for a horizontal greenery layout. Compared to scenarios without greenery, buildings with vertical greenery experience a maximum reduction of 0.66 °C in outdoor air temperature and 0.72 °C in indoor air temperature, along with a 5.9 % decrease in energy consumption and carbon emissions. This study addresses urban challenges through a quantified vertical greenery design, offering valuable insights for sustainable urban development.

Field measurement study of indoor thermal environment of badminton halls in a hot summer and cold winter region in different seasons in China

The indoor thermal environment has a direct impact on human thermal comfort and health. In order to assess the status of the indoor thermal environment of typical sports buildings in hot summer and cold winter climate zones in China, 14 badminton halls in 10 cities in Hubei Province (including 5 venues in Wuhan) in this climate zone are chosen as research objects for field testing of indoor thermal environment parameters in 4 seasons. All the tested stadiums are naturally ventilated in non-event conditions. The results reveal that the average indoor temperature of badminton halls in summer is excessively high (i.e., 31.89 °C), which is higher than the regulation specified in JGJ31-2003 or GB-T18883-2022 on the reference interval of the indoor air temperature of venues in summer, (i.e., (26–28 °C) or (22–28 °C), respectively). The average indoor temperature of badminton halls in winter is too low (i.e., 12.95 °C), and it is lower than the recommendations of JGJ31-2003 or GB-T18883-2022 on the reference interval of the indoor air temperature of venues in winter (i.e., (16–18 °C) or (16–24 °C), respectively), relative humidity and air velocity are in the thermal comfort interval for all seasons, and the indoor thermal environment factors of badminton courts in spring and autumn meet the comfort requirements. The indoor and outdoor temperatures and the relative humidity of badminton courts are highly correlated. The indoor temperature and relative humidity vary according to changes in those factors outdoors, whereas the air velocity is not affected by outdoor changes. In the hot summer and cold winter climate zones, some discrepancies in the indoor temperature variation patterns of badminton halls at various altitudes are detectable. The results of this study aim to provide a solid basis for the development of indoor thermal-comfort standards for sports stadiums in China.

Effects of indoor plants on CO2 concentration, indoor air temperature and relative humidity in office buildings.

This experimental study investigates the influence of indoor plants on three aspects of air quality in office spaces: relative humidity, indoor air temperature, and carbon dioxide concentration. Employing a Latin square design, we rotated three different treatments across three offices over six time periods. These treatments included a control (no plants), a low-volume treatment (five plants), and a high-volume treatment (eighteen plants) of Nephrolepis exaltata (Boston fern). Air quality parameters were continuously monitored at five-minute intervals using Trace Gas Analyzers. Generalised linear mixed modelling (GLMM) was employed to examine the effect of each treatment on relative humidity, indoor air temperature and CO2 concentration. We observed a significant positive correlation between the number of indoor plants and relative humidity levels. In offices without any plants, the median relative humidity was 29.1%. This increased to 38.9% in offices with 5 plants and further to 49.2% in offices with 18 plants. However, we did not find significant associations between the number of indoor plants and indoor air temperature or corrected CO2 concentration. Our research provides support for the use of indoor plants to increase relative humidity, which can have health benefits in dry climates, but does not provide support for using indoor plants to regulate indoor air temperatures or CO2 concentration in office environments.

Application of neural networks to predict indoor air temperature in a building with artificial ventilation: impact of early stopping

Application of neural networks to predict indoor air temperature in a building with artificial ventilation: impact of early stopping

Evaluation of microclimate in dairy farms using different model typologies in computational fluid dynamics analyses

Ventilation plays a key role in the livestock buildings since it is important to guarantee a comfortable environment and adequate indoor air quality for the animals. Naturally ventilated barns are usually characterized by high variability in the ventilation conditions. Moreover, the ventilation efficiency can be very different in different areas of a barn because of the different presence of the animals. On the other hand, appropriate ventilation is an essential requirement to ensure animal welfare and efficient and sustainable production since a proper ventilation is the most efficient way to remove undesirable air pollutants and to obtain a comfortable microclimate for the welfare of the animals. In this regard, the computational fluid dynamic (CFD) simulations represent a powerful and useful tool because they can be used to assess ventilation and microclimate conditions. In this context, the present study has the object to assess whether different CFD modelling approaches (i.e. model with animals modelled as obstacles with closed volume and model enriched with cows modelled as obstacles capable of exchanging heat with the surrounding air volume) show differences in relation to the climatic conditions inside a naturally ventilated dairy barn. The comparison of the results, set in terms of indoor air temperature and air velocity contours of the two different models, arises that if a precise definition of the microclimatic features is necessary, in order to correlate them with production parameters or assess animal welfare indexes, thermal simplification is not acceptable since can lead to completely misleading conclusions and incorrect evaluations. Then, only adopting CFD models considering the animal thermal behaviour is possible to obtain effective information both for the proper barn system management and for the creation of useful tools driving the farmers' choices.

Thermal and energy performance assessment of naturally ventilated roofs with phase change material

The effect of incorporating phase change material (PCM) into roofing systems combined with natural ventilation is numerically and experimentally investigated. Four roof configurations, including ventilated and unventilated options with and without an air gap between the PCM and the insulation material, are subjected to experimental research during the winter season in a semi-arid climate using two fully instrumented modules. A sensitivity analysisis conductedthrough annual transient simulations fordifferentair gap dimensions and schedule openings. The experimental campaign demonstrates a decrease in the maximum peak indoor air temperature of between 1.9 and 4.4 %when the PCM is employed. Additionally, an increase in the minimum indoor air temperature between 4.4 and 10.4 % is achieved. Similarly, an improvement in the thermal performance of the PCMis observedwhen natural ventilation occurs, and it positively influences the interiorsurface temperature of the roof.Furthermore, the numerical results show almost zero annual thermal balance in the scenario where natural ventilation is allowed in the combination of 12 and 24 h per day through ducts with a diameter of 15 and 20 cm, respectively. Finally, this demonstrates that PCMroofs enhanced with natural ventilation could be an energy-efficientalternative for semi-arid climates under well-configured ventilation schedules and roof layers.

Towards Sustainable Living through Thermoneutral Temperature Management in Subtropical Steppe Climates

This study addresses the critical interplay between sustainable living and thermal comfort within residential buildings in subtropical steppe (BSh) climates, particularly in Northern Iraq. With the global imperative to enhance energy efficiency and occupant well-being, this research emphasizes the identification of thermoneutral indoor air temperature ranges that both support sustainable energy use and ensure the occupants’ thermal comfort. By analyzing the acceptable temperature limits across different building orientations during summer and winter, the study utilizes the predicted mean vote–predicted percentage dissatisfied (PMV-PPD) index approach to establish thermal comfort thresholds. The findings reveal that the optimal summer and winter indoor air temperatures are 29.2 °C and 19.4 °C, respectively, with variations across orientations highlighting the significant influence of building directionality on achieving thermoneutral conditions. A wider range of accepted temperatures exists in the eastward orientation in summer (between 26.6 °C and 29.2 °C). The study advances our understanding of sustainable thermal comfort practices, proposing orientation-specific temperature ranges as a cornerstone for reducing energy consumption without compromising occupant comfort in subtropical steppe climates.

Assessment of thermal performance of energy-active window systems in hot climates

Window systems, particularly in hot climates, are the source of considerable heat transfer that affects the buildings’ indoor environment and energy consumption. Proper design and optimization of its thermal performance significantly contribute to the overall envelope energy performance. Using a multi-layer glazing system, Energy Active Window (EAW) adapts window insulation technology to reuse low-grade air from the HVAC system, keeping the temperature at the internal surface of the window close to the indoor air temperature, minimizing heat exchange between indoor and outdoor. This study aims to reduce energy consumption by optimizing EAW to increase its thermal resistance by channeling the return air (RA) from the HVAC system into the curtain frame, thereby lowering the temperature of the air gap and air film layer. The study examined the window system’s exhaust/return air behavior using the Computational Fluid Dynamics (CFD) tool (Fluent) to simulate the heat exchange between outdoor and indoor building environments. The CFD simulation was validated using experimental measurements. Results show a surface temperature decrease of 4 to 7 °C based on the inner and outer pane airflow conditions when the outdoor temperature is 45 °C with an 8 % margin of error. Various EAW components were tested, including air velocity, air–gap width, volume, and outdoor temperatures, examining both triple and double-glazing layers.

Performance assessment of the curved-type multi-channel PV roof for space-heating and electricity generation in winter

The curved-type PV roof integrated with flexible PV tiles is a novel attempt to implement the building-integrated photovoltaic/thermal technology into diverse genres of architectural design. To explore its performance in the function of electricity generation and space-heating, different ventilation configurations of the air channels are adopted in the design of the multi-air-channels of the system; two working modes (fresh-air-heating - FAH and recirculated-air-heating - RAH) are applied in the system's operation. The case study is based on a residential building linked with the system in Hefei, China. The performance assessment is conducted on a typical sunny winter day and through the winter of the Typical Meteorological Year. The investigation results indicate that RAH mode has the potential to raise the indoor air temperature to a greater extent. However, the electrical power output shows a disadvantage due to the relatively poor PV cooling effect; increasing the connection air channels could enhance the indoor air heating but add the fan power consumption. The prediction throughout winter manifests that the all-in-parallel connection produces 1827.63 kWh (FAH) and 1574.55 kWh (RAH) of total energy, whereas the 6-in-series connection produces 2085.91 kWh (FAH) and 1618.99 kWh (RAH).

The impact of local microclimates and Urban Greening Factor on schools’ thermal conditions during summer: A study in Coventry, UK

Thermal comfort in schools affects children's wellbeing and educational outcomes. Global warming and frequent heatwaves have worsened the overheating issue in schools, especially in Western European countries, like the UK. While previous studies have mainly focused on residential and commercial buildings, school-related research often emphasised indoor thermal conditions, neglecting the broader influence of microclimates on the overall thermal conditions. Therefore, this research explores the thermal conditions in schools, during the summer of 2023, with a specific focus on the impact of greenery and materials. Urban Greening Factor (UGF) and its relationship with indoor and outdoor air temperatures were explored for the first time.Field studies were conducted in four primary schools in Coventry, UK, measuring indoor air temperatures and micrometeorological parameters. Tree shade demonstrated a substantial cooling effect, reducing air temperature and mean radiant temperature by up to 6.4 °C and 22.9 °C, respectively. Considerable difference between measured air temperatures in sunlight and official meteorological records highlights the need for microclimatic studies in schools. Thermal imagery identified high surface temperatures on artificial grass (67 °C) and asphalt (55 °C). Urban Greening Factor showed a strong correlation with classroom temperatures but failed to account for spatial greenery distribution and subsequently outdoor thermal conditions. The study concludes that optimising tree shade and replacing dark and artificial materials, are necessary for effective heat mitigation, offering valuable insights for policymakers and urban planners to create thermally comfortable and sustainable school environments.

Analyzing the thermal performance of walling systems in low-income housing through computational fluid dynamics approach

The thermal properties of wall materials have a direct impact on the thermal performance of the indoor environment, by also influencing the occupant’s well-being. Coupled with airflow dynamics, the thermal performance of wall materials influences the indoor air temperature distribution thereby impacting thermal comfort, particularly in naturally ventilated (NV) spaces. However, defining the relationships between the wall characteristics, airflow dynamics, and thermal comfort for selecting the appropriate wall material for low-income NV buildings is still not evident in the current literature. Therefore, this study proposes a simulation-based framework that considers the relationships between wall materials, airflow dynamics, and thermal comfort using a computational fluid dynamics (CFD) approach by spatially plotting the thermal comfort within the NV spaces.The study analyses locally accessible wall materials, subjecting them to different operating conditions within NV dwelling units of low-income housing in India. Out of the analyzed wall materials, aerated autoclaved blocks exhibited a significant indoor temperature reduction of 20.7 % compared to the compressed stabilized earth blocks, with constrained airflow exacerbating temperature fluctuations. The global implications of these findings are substantial for urban low-income dwellers experiencing excessive heat. Mass housing efforts worldwide can benefit from using thermally efficient materials in construction thereby improving living conditions, and mitigating the impact of climate change on thermal comfort and health.

Thermal conditions and daylight availability in different zones of courtyard buildings; a study in Iran

ABSTRACT Passive design strategies enhance indoor thermal comfort and reduce energy consumption in buildings located in hot climates. Thus, exploring the various zones of a house’s yard can yield valuable insights for devising a plan that achieves high energy and lighting efficiency. This study examines the climate-responsive design strategies of 20 traditional courtyard buildings in Birjand’s hot and dry climate. These courtyard houses informed modelling a new hypothetical house in DesignBuilder. Two main orientations (45° = NE–SW, and 315° = NW–SE) were used for comparing their impact on indoor air temperature, solar gain and daylight factor across various courtyard zones. The findings indicate that during winter, the interiors of courtyard houses maintain a temperature higher than the exterior, while in summer, they remain cooler than outside conditions. Concerning the influence of orientation on indoor climates, the NE–SW orientation yielded the greatest solar gains for windows in the northern and western zones. Conversely, in the NW–SE orientation, the most substantial solar gains were recorded for windows in the northern and eastern zones. Additionally, the study noted a marginal variation in the daylight factor across different zones of the courtyard houses when comparing the two orientations.

DATAWARE AND SOFTWARE OF THE AUTOMATED TECHNOLOGY FOR COMPUTER- INTEGRATED CONTROL OF HEAT PUMP SYSTEMS

The paper has solved a scientific and applied problem as for substantiating requirements to technical and functional characteristics of the automated technologies of computer-integrated control of heat pump systems in the heating and cooling modes owing to its dataware and software developing and testing. Following functional procedures have been taken into consideration during the dataware and software development of the computer-integrated subsystem for heating of buildings: monitoring of ambient air temperature, ground temperature, and operating modes of functional elements of the heat pump system as well as zonal monitoring of indoor air temperature; computer-integrated processing of the monitoring data; automated control of the heat pump as well as modes of zonal thermal medium supply to the building; and analysis of energy efficiency as for implementation of the proposed computer-integrated method to control systems of thermodynamic heating. It has been identified that thermal capacity of a heat pump is rather sensitive to indicators of the total heat losses of a building. If the total heat losses increase from 0.2°С/hour up to 0.5°С/hour then constant value of the thermal capacity increases by 48%. Moreover, thermal capacity of a heat pump is quite sensitive to ambient air temperature dynamics: if temperature variation is 12°С (i.e. 3°С-9 °С) then average increase in thermal capacity is 58 %. Following functional procedures have been involved during the dataware and software development of the computer-integrated subsystem for cooling of buildings: monitoring of ambient air temperature and operating modes of functional elements of the heat pump system; zonal computer-integrated monitoring of indoor air temperature; computer-integrated the monitoring data processing based upon microcontrollers; automated control of the thermal pump operating modes (i.e. heat energy outfeed and release to the main intercooler unit); and analysis of energy efficiency as for implementation of the proposed computer-integrated method to control systems of thermodynamic cooling of buildings. The abovementioned has helped identify that thermal capacity of a heat pump is rather sensitive to indicator of heat exchange with surrounding air: four times increase in heat-exchange coefficient (i.e. from 1°С/hour up to 4°С/hour) results in 20% growth of thermal capacity of the cooling subsystem system at similar ambient air temperature (it varies from 30°С up to 36 °С) if the maintained target indoor temperature is 22°С.

Assessment of the impact of setting the heating curve on reducing gas consumption in a residential building while ensuring thermal comfort

Due to the large share of the residential building sector in CO2 emissions, it is necessary to look for quick-to-implement and cost-free solutions for heating systems aimed at increasing their efficiency and reducing fuel consumption. The aim of the study is a multi-aspect assessment of the proper setting of the heating curve in the weather controller of a low-temperature floor heating system with a condensing gas boiler, and an analysis of the impact of the heating curve slope on the natural gas consumption, the emission of gaseous and dust pollutants and on maintaining appropriate indoor air parameters: air temperature, operative temperature and PMV and PPD. A wide range of simulation tests were carried out using the TRNSYS software for an existing energy-efficient single-family residential building, with mechanical ventilation with heat recovery, located in north-eastern Poland in Bialystok. Changing the heating curve slope by 0.1 can reduce gas consumption and pollutant emissions by 1.6–10.3 %. Low heating curve slopes may result in failure to reach the temperature set by users (difference between the set and achieved indoor temperature up to 1.9 K), while maintaining standard thermal comfort parameters (−0.5<PMV<+0.5; PPD<10 %). Reducing the indoor air temperature by 2 K can contribute to reducing gas consumption by 11 % while maintaining standard thermal comfort parameters. Changing the heating curve slope is one of the effective methods of reducing fuel consumption in the building. Results are useful for users of buildings equipped with low-temperature heating systems with floor heating and installers of these systems.

Comparison of data-driven stochastic window operation models for residential buildings

In residential buildings, window opening is typically one of the most significant parameters that affects indoor air temperature and thus the energy required for heating and cooling. While several field measurement campaigns have been undertaken, and datasets have been used to calibrate data-driven stochastic models based on different techniques, a critical comparison between these window operation models, analysing their suitability for building energy simulation, is needed. This study compares seven different modelling approaches including Gaussian distribution function, logistic regression, Markov chain, Markov-logit hybrid, classification tree, artificial neural network and random forest, trained and tested using measurements of 21 living rooms and 10 bedrooms from residential buildings located in Australian subtropical and temperate climates. Two types of modelling approaches were tested: individual, where each window operation was modelled individually, and cohort, where a common model was developed considering all the windows in the dataset. The stochastic nature of window opening was introduced to the models by Monte Carlo methods. True Positive Rate (TPR) and True Negative Rate (TNR), quantified using the Area Under Curve (AUC) method, were used to benchmark the performance of the different models. The classification trees and random forest were identified as more accurate methods (>0.74 median AUC) for cohort modelling, while artificial neural network and Markov-logit hybrid methods were identified as more accurate methods (>0.7 median AUC) for individual window operation modelling in building simulation applications.

Multi-factor thermal analysis of phase change material integrated roofing elements

In the present study, the PCM layer is integrated into the roof, analyzed, and compared for its thermal behaviour in terms of Indoor Air Temperature Reduction (IATR), Thermal Load Levelling (TLL), and Lag Time (LT) to determine the ideal position, thickness, and type of PCM. The observations from the experimental analysis were validated using COMSOL Multiphysics v6.0 with available literature. The results showed that PCM-integrated roofs reduced the interior temperature by around 30%. Furthermore, the fluctuations in the interior temperatures were reduced to 6.1% with PCM integration within the roof. A lag time of 5–8.25 h was observed for the PCM roofs. The study also found that the material properties impact the overall thermal behaviour of the PCM-integrated roofs. These properties were further explored using continuous cyclic thermal loading and variation of latent heat over a period of four days for three climatic zones in India. Abbreviations: PCM: Phase Change Material; CC: Conventional Concrete; AAC: Autoclaved Aerated Cement; TMY: Typical Meteorological Years; epw file: Energy Plus Weather File; mPCM: Microencapsulated Phase Change Material; PTC: Positive Temperature Coefficient; DHT: Digital Temperature And Humidity; IATR: Indoor Air Temperature Reduction (%); TLL: Thermal Load Levelling (%); LT: Lag Time (hours)

Indoor Air Temperature Distribution and Heat Transfer Coefficient for Evaluating Cold Storage of Phase-Change Materials during Night Ventilation

Indoor Air Temperature Distribution and Heat Transfer Coefficient for Evaluating Cold Storage of Phase-Change Materials during Night Ventilation

Exploring public perceptions of indoor air quality under different quasi-experimental conditions: a UK case study

ABSTRACT The fast-growing sensing technology means there is an extensive range of low-cost indoor air quality (IAQ) devices or sensor modules readily available on the commercial market. However, less attention has been paid to exploring people’s perceptions and responses to indoor air pollution. Such knowledge is deemed important for improving the design of future IAQ sensors, enhancing public awareness and providing guidance on ways to improve indoor environmental conditions. This study aimed to explore people’s perceptions and responses to IAQ under different quasi-experimental environmental conditions and levels of information. The study is reported from the perspective of 16 staff and students at a UK university, held within a prototype smart and modular home built on campus. It compares questionnaire survey responses and focus group interview discussions with actual IAQ concentrations and other influential indoor parameters (indoor air temperature and relative humidity). Study outcomes revealed the importance of understanding contextual factors when developing feedback and communication strategies to best improve people’s awareness, acceptance, and behavioural responses to IAQ. Findings highlight the usefulness of focus group discussions in the design of future IAQ sensors.

Seasonal Variations in Radon and Thoron Exhalation Rates from Solid Concrete Interior Walls Observed Using In Situ Measurements

Building materials, such as brick and concrete, are known indoor radon (222Rn) and thoron (220Rn) sources. Most radon and thoron exhalation studies are based on the laboratory testing of pieces and blocks of such materials. To discuss if laboratory findings can be applied to a real-world environment, we conducted intensive in situ exhalation tests on two solid concrete interior walls of an apartment in Japan for over a year. Exhalation rates of radon (JRn) and thoron (JTn) were measured using an accumulation chamber and dedicated monitors, alongside monitoring indoor air temperature (T) and absolute humidity (AHin). There were weak correlations between JRn or JTn and T or AHin at one tested wall, and moderate correlations of JRn and strong correlations of JTn with T or AHin at the other wall, meaning more or less seasonal variations. The findings aligned with previous laboratory experiments on JRn but lacked corresponding data for JTn. Additionally, a moderate or strong correlation between JRn and JTn was observed for both tested walls. Comparison with theoretical calculations revealed a new issue regarding the impact of each process of emanation and migration within concrete pores on radon and thoron exhalation. Overall, this study provides insight into parameterizing radon and thoron source inputs in modeling the spatiotemporal dynamics of indoor radon and thoron.

Assessment of the impact of interior insulation on exterior walls in three Swedish buildings – based on validated models

This project evaluates the impact of interior insulation on external walls in three Swedish heritage buildings. Field measurements and hygrothermal simulations were conducted to assess available solutions. Measurements of temperature and relative humidity were taken both indoors and outdoors, as well as on the exterior and interior surfaces of the walls. The accuracy of simulation standards for indoor air temperature and relative humidity was evaluated, and the findings indicate that current simulation standards can serve as reliable alternatives when on-site measurements are not feasible. Validated models were used to analyze the impact of 13 different interior insulation solutions, including vapor-tight and open options, some of which were capillary active. The results highlight that the risk of moisture damage depends on the design of the existing external wall and indicate the importance of hydrophobic treatment in mitigating risks. Thinner amounts of interior insulation can significantly reduce transmission losses without compromising moisture performance. Overall, all the assessed external walls can be safely insulated from the interior, although hydrophobic treatment is recommended for optimal results. This research provides practical insights for decision-making in simulation approaches and optimizing insulation strategies to enhance the performance and durability of external walls in building projects.