Search Results (110)

Creating a comfortable microclimate in the premises of buildings is currently becoming one of the priorities in the field of architecture, construction and engineering systems. The increased attention from the scientific community to this topic is due not only to the desire to ensure healthy and favorable conditions for human life but also to the need for the rational use of energy resources. This area is becoming particularly relevant in the context of global challenges related to climate change, rising energy costs and increased environmental requirements. Practice shows that any technical solutions to ensure comfortable temperature, humidity and air exchange in rooms should be closely linked to the concept of energy efficiency. This allows one not only to reduce operating costs but also to significantly reduce greenhouse gas emissions, thereby contributing to sustainable development and environmental safety. In this connection, this study presents a parametric assessment of the influence of climatic and geometric factors on the aerodynamic characteristics of the air cavity, which affect the heat exchange process in the ventilated layer of curtain wall systems. The assessment was carried out using a combined analytical calculation method that provides averaged thermophysical parameters, such as mean air velocity ($V_s$), average internal surface temperature ($t_{in.s}^{av}$), and convective heat transfer coefficient (${\alpha }_s$) within the air cavity. This study resulted in empirical average values, demonstrating that the air velocity within the cavity significantly depends on atmospheric pressure and façade height difference. For instance, a 10-fold increase in façade height leads to a 4.4-fold increase in air velocity. Furthermore, a three-fold variation in local resistance coefficients results in up to a two-fold change in airflow velocity. The cavity thickness, depending on atmospheric pressure, was also found to affect airflow velocity by up to 25%. Similar patterns were observed under ambient temperatures of +20 °C, +30 °C, and +40 °C. The analysis confirmed that airflow velocity is directly affected by cavity height, while the impact of solar radiation is negligible. However, based on the outcomes of the analytical model, it was concluded that the method does not adequately account for the effects of solar radiation and vertical temperature gradients on airflow within ventilated façades. This highlights the need for further full-scale experimental investigations under hot climate conditions in South Kazakhstan. The findings are expected to be applicable internationally to regions with comparable climatic characteristics. Ultimately, a correct understanding of thermophysical processes in such structures will support the advancement of trends such as Lightweight Design, Functionally Graded Design, and Value Engineering in the development of curtain wall systems, through the optimized selection of façade configurations, accounting for temperature loads under specific climatic and design conditions. Full article

The Life Cycle Cost Assessment (LCCA) methodology is widely used to determine the optimal thickness of thermal insulation for walls and roofs. The results depend on several factors, such as the degree day calculations method, the ambient or sol–air temperature, base temperature variations, and the heat capacity of the thermal envelope elements. This study aims to analyze the impact of solar radiation on mass walls with different orientations in five cities in northern Chile, which have severe solar climates. The goal is to determine the optimal thickness of expanded polystyrene insulation using the LCCA method, considering solar radiation, a varying base temperature, and validating results by analyzing the energy demand for heating and cooling of a typical house. The findings show that excluding solar radiation in the LCCA methodology can lead to an underestimation of the optimal insulation thickness by 21–39% for walls in northern Chile. It was also found that using variable monthly threshold temperatures for heating and cooling based on the adaptive thermal comfort model results in a slight underestimation (1–3%) of the optimal thickness compared to a constant annual temperature. An energy simulation of a typical house in five cities in northern Chile showed that neglecting the effect of solar radiation when determining the thermal insulation thickness for the studied wall can lead to a minor increase in heating and cooling energy demand, ranging from approximately 1% to 9%. However, this study emphasizes the importance of applying optimal insulation thickness for cities with more continental climates like Santiago and Calama, where the heating demand is higher than cooling. Full article

Greenhouses offer optimal environments for crop cultivation during the winter months. The rationale for this study was identified as the synergistic exchange of air between the soil, the wall, and the indoor environment within the greenhouse (referring to the coupling law of the temperature fields of the three elements in space and time, including the direction of heat transfer and the consistency of the temperature zoning), thereby maintaining a more optimal temperature. However, there is a paucity of research on the impact of different spans on the thermal environment in solar greenhouses and even fewer studies on the synergistic law of changes in soil-wall indoor air in solar greenhouses with different spans. In this study, two solar greenhouses with different spans were analyzed through a combination of experiments as follows: K-means classification optimized using the grey wolf optimizer (GWO), computational fluid dynamics (CFD) simulations, and long short-term memory (LSTM) prediction models. The two solar greenhouses, designated as S1 and S2, had spans of 11 m and 10 m, respectively. The results are as follows: In two greenhouses when the span and temperature were the same, the indoor air temperature and soil temperature of the S1 greenhouse were lower than those of the S2 greenhouse; there was an isothermal layer in the north wall of greenhouses S1 and S2 (a stable area where the temperature change over time is less than 0.5 °C), the horizontal distance between the isothermal layer on the inside of the greenhouse wall and the inside of the wall was more than 400 mm, and that of the outside of the greenhouse wall was more than 200 mm; within the solar greenhouse, this study identified that heat was emitted from the inner surface of the wall (at 0 mm from the inner surface) toward the outer surface of the wall (at 0 mm from the outer surface), as well as at a horizontal distance of 200 mm from the inner surface of the wall. The temperature data from 0:00 to 8:00 at night were selected for the purpose of analyzing the temperature synergistic change in soil-wall indoor air in the S1 greenhouse. The temperature change can be classified into four categories according to K-means classification, which was optimized based on the grey wolf algorithm. The categories were as follows: high-temperature region, medium-high temperature region, medium-low temperature region, and low-temperature region. The low-temperature region spanned the range of X = (800, 3000) mm, and its height range was Y = (−150, 1200) mm. The CFD model and LSTM prediction model have been shown to be superior, and the findings of this study offer a theoretical basis for the optimization of thermal environment control in solar greenhouses. Full article

With rapid global urbanization, glass curtain wall buildings have been widely adopted due to aesthetics and natural lighting. However, during summer time, intense solar radiation leads to significant indoor heat gain, which adversely affect thermal comfort and energy efficiency. The conventional air conditioning systems are typically equipped with a cooling capacity sufficient to maintain an indoor air temperature at the design values specified in the Design standard for energy efficiency of public buildings, which fails to account for the effects of radiation temperature, potentially resulting in reduced thermal comfort and energy inefficiency. By integrating the Thermal Comfort Tool to calculate the PMV index, this study evaluates the affection of solar heat gain on indoor occupants’ thermal comfort and proposes an optimized air temperature control strategy to realize thermal comfort. Based on the dynamic air temperature strategy, an energy consumption model is developed to evaluate the affection of solar radiation on energy consumption for glass curtain wall buildings based on the PMV index. The synergistic effects of shading measures are then evaluated. This study conducts simulation analysis using an office building with a glass curtain wall located in Beijing as a case study. When accounting for radiant heat gain, a significant portion of the time (53.89%) fall outside the thermal comfort range, even when the air conditioning is set to the designated temperature. To maintain thermal comfort, the air conditioning temperature must be lowered by 1.4–3.5 °C, resulting in a 28.08% increase in energy consumption. To address this issue, this study finds that installing interior shading can reduce radiant heat gain. Under the same thermal comfort conditions, the required air temperature reduction is only 0.8–2.1 °C, leading to a 24.26% reduction in energy consumption compared to the case without interior shading. Full article

This study initially examined the thermal comfort of rural residents in southern Jiangsu, analyzing their tolerance levels and expected temperature ranges during winter and summer. Subsequently, Design Builder 7.02.004 software was utilized to simulate the energy consumption of typical residential buildings. Furthermore, an orthogonal test method was employed to investigate the significant relationships among seven factors influencing building energy consumption in both winter and summer. These factors include external wall heat transfer coefficient, roof heat transfer coefficient, external window heat transfer coefficient, external window solar heat gain coefficient (SHGC), window-to-wall-area ratio, air tightness, and building orientation. Finally, based on the findings from the thermal comfort study, recommended passive design parameters for near-zero-energy residential buildings in southern Jiangsu were proposed. This provides valuable references for the future construction efforts of such buildings within this region. Full article

The Trombe Wall (TW) has gained recognition for its simplicity, efficiency, and zero operational costs, making it a key contributor to Sustainable Development Goals (SDGs) 7 and 11 by enhancing energy access and providing sustainable heating solutions. This passive solar technology is particularly beneficial in rural areas, offering cost-effective thermal comfort while minimizing environmental impact. This study evaluates the performance of three TW configurations attached to a room, designed with inclined glazing relative to the vertical air layer and stone layers at the bottom acting as thermal mass, commonly used in rural installations in Peru. Using 2D Computational Fluid Dynamics, the analysis compares an inclined heated wall with guided vanes featuring three or five blades to a configuration without vanes. Results show that the three-blade guided flow configuration achieves the highest temperature rise of 4 °C, with a reference temperature of 20 °C, under an absorber heat flux of 200–400 W/m², albeit with a slightly lower flow rate of 0.17–0.23 kg/s compared to the configuration without guided flow. The maximum thermal efficiency of 57.90% was observed for the three-blade configuration, which is 2.26% higher than the efficiency of the configuration without guided flow, under an absorber heat flux of 400 W/m². The obtained path-lines reveals that the three-blade configuration minimizes flow detachment, nearly eliminates recirculation near the bottom corner of the glazing, and reduces the separation bubble at the top corner of the massive wall near the outlet. These findings highlight the potential of guided vanes to enhance the performance of Trombe Walls in rural settings. Full article

The aim of this study is to address the lack of comprehensive analysis methods for multi-functional Trombe wall systems. The objective is to establish an integrated evaluation system that assesses thermal, purification, and power generation performance. This study introduces a novel multi-objective analysis method coupling energy and exergy efficiency for three types of Trombe wall structures: traditional, thermal-catalytic (TC), and TC–photovoltaic (TC-PV). This study simultaneously monitors heat transfer, formaldehyde degradation, and photovoltaic power generation performance. A key novelty is the introduction of a quantitative index for “purification efficiency” and the revelation of the co-evolution law between PV (photovoltaic) coverage and the three types of efficiency for the first time. This study evaluates three cases: traditional, TC, and TC-PV Trombe walls. The results show that the thermal efficiencies of the three Trombe walls are 47.2%, 41.9%, and 51.7%, respectively, with corresponding thermal exergy efficiencies of 0.59%, 0.49%, and 0.63%. The TC and TC-PV Trombe walls achieve purification efficiencies of 57.0% and 53.0% and purification exergy efficiencies of 2.53% and 2.42%, respectively. The TC-PV Trombe wall has electrical and electrical exergy efficiencies of 16.0% and 12.84%, respectively. System structure optimization analysis indicates that the system achieves the best exergy efficiency when the solar irradiation is 400 W/m² and the air channel thickness is 0.05 m. Additionally, the purification exergy efficiency increases with higher formaldehyde concentrations, while thermal, purification, and electric exergy efficiencies all increase with greater PV coverage. Exergy loss analysis reveals that the TC layer and heat-absorbing plate are major sources of loss. Therefore, developing catalytic materials with high absorptivity and high catalytic activity could enhance the system’s exergy efficiency. Full article

With the increasing demand for energy-efficient and sustainable building materials, innovative cooling technologies have become a key focus in the construction industry. This study developed a double-layer cooling coating integrating evaporation and radiation mechanisms. The first layer consists of a TiO₂/PUA radiation layer, where rutile TiO₂ is incorporated into polyurethane acrylate (PUA) resin to enhance solar reflectivity. The second layer is a P(NVP-co-NMA) hydrogel, which evaporates water at high temperatures and absorbs moisture from the air at low temperatures, eliminating the need for additional water supply systems. The TiO₂/PUA@P(NVP-co-NMA) coating demonstrates high solar reflectivity and infrared emissivity, effectively reducing indoor temperatures by dissipating heat through water evaporation and radiative cooling. Testing showed a temperature reduction of approximately 7.6 °C in a small house with this coating under simulated conditions. This material demonstrates favorable properties that may make it suitable for applications on building roofs and exterior walls, potentially addressing some limitations of conventional evaporative or radiative cooling systems. Its observed multi-effect cooling performance indicates promise for contributing to energy savings in sustainable building designs. Full article

Energy savings issues are important in the context of building operation. An interesting solution for the southern external walls of the building envelope is the thermal storage wall (TSW), also known as the Trombe wall. The article considers four variants of the wall structure, including three containing phase change material (PCM). The purpose of this study was to determine the influence of the amount and location of phase change material in the masonry layer on the storage and flow of heat through the barrier. Each wall is equipped with a double-glazed external collector system with identical physical parameters. The research was carried out in specially dedicated testing stations in the form of external solar energy chambers, subjected to real climatic loads. The distribution of the heat flux density values was determined using experimental tests and was subjected to comparative analysis for the various variants considered using statistical analytical methods. A comparative analysis was performed between the heat flux density values obtained for each barrier in the assumed time interval from the one-year research period. The Kruskal–Wallis test and the median test were used for analyses performed in the Statistica 13.3 programme. The purpose of these analyses was to determine the occurrence of significant differences between individual heat flux flows through the barriers tested. The results obtained indicate that the use of PCM in thermal storage walls extends the time required to transfer the accumulated heat in the barrier to the internal environment while reducing the amplitude of the internal air temperature. Full article

Urban heat islands (UHIs) increase urban warming and reduce outdoor thermal comfort due to changing surface characteristics and climate change. This study investigates the role of green walls (GWs) in mitigating UHI, improving outdoor thermal comfort, and reducing carbon emissions under current and future (2050) scenarios. Focusing on Via della Consolata, Turin, Italy, the study combines remote sensing for UHI detection and numerical simulations for thermal analysis during seasonal extremes. The results show that GWs slightly reduce air temperatures, with a maximum decrease of 1.6 °C in winter (2050), and have cooling effects on mean radiant temperature (up to 2.27 °C) during peak summer solar radiation. GWs also improve outdoor comfort, reducing the Universal Thermal Climate Index by 0.55 °C in the summer of 2050. The energy analysis shows that summer carbon emission intensity is reduced by 31%, despite winter heating demand increasing emissions by 45%. The study highlights the potential of GWs in urban climate adaptation, particularly in dense urban environments with low sky view factors. Seasonal optimization is crucial to balance cooling and heating energy demand. As cities face rising temperatures and heat waves, the integration of GWs offers a sustainable strategy to improve microclimate, reduce carbon emissions, and mitigate the effects of UHI. Full article

A whole series of factors influence the temperature of the soil surface and surface layers. The soil surface is heated by solar radiation during the day. It radiates some of the obtained heat at night. The heat exchange between the soil and the atmosphere depends on the air and soil temperatures and the speed of air movement. Precipitation may also affect surface soil layers, but this was not considered in this study. In the mentioned interaction, a specific temperature field of the surface layers of the soil is established. To increase the building’s energy efficiency, the aim is to optimize the operation of its heating and cooling systems and to reduce heat loss to the environment as much as possible. Heat loss through the floor of the building or the walls of the recessed part into the ground changes the established temperature field of the ground. The heat spreads in the soil and is given to the atmospheric air. During the research, to validate the numerical model, the heat flow density was analysed to determine how it changes while maintaining a constant temperature of the heating surface at a certain depth of the soil. It was found that the new thermodynamic equilibrium, depending on the seasonality, can be reached in a time interval of up to a week. The temperature change in the artificially limited volume of the ground under the building or next to it can be treated as the work of the ground thermo-accumulator: its charge or discharge by heat. This makes it possible to reduce the annual energy costs of the building by more than ten percent. Full article

Although the European residential sector has promoted various heating and cooling passive solar systems in many ways, ongoing climate changes affect these construction elements at an annual level. Using the weather files for three years in the recent past (2018, 2021 and 2023), this paper numerically investigates the energy, environmental and economic performance of two small single-family houses equipped with Trombe walls and fixed horizontal overhangs of different depths (0 m, 0.25 m, 0.5 m, 0.75 m and 1 m) for two characteristic European climate zones: continental (Kielce city, Poland) and moderate continental (Kragujevac city, Serbia). Both houses were created in Google SketchUp 8 software using current Statistical data and Rulebooks of energy efficiency, while adopted heating (gas boiler and radiators) and cooling (individual air-conditioning units) active thermo-technical systems were simulated in EnergyPlus 7.1 software using official specific energy, environmental and economic indicators. Compared to the appropriate reference houses—without mentioning passive solar systems—the main results of this study are as follows: (1) higher outdoor air temperatures can reduce final (thermal) energy consumption for heating by 37.74% (for the Kielce climate zone) and 52.49% (for the Kragujevac climate zone); (2) higher outdoor air temperatures can increase final (electricity) energy consumption for cooling between 5.71 and 11.75 times (for Kielce) and 4.36 and 9.81 times (for Kragujevac); (3) percentage savings of primary energy consumption and monetary savings are highest when houses are equipped with Trombe walls and 1 m deep overhangs; and (4) all considered cases of passive solar systems do not contribute to the reduction of greenhouse gas emissions. Since climate change is a consequence of greenhouse gas emissions, priority should be given to environmental indicators in future investigations. Full article

The solar heat gain is an important component of building cooling load, and its magnitude affects building energy consumption directly. In buildings with glass curtain walls, the window to wall rate is close to 1, so the amount of solar heat gain is huge, which directly determines the energy consumption level of a building’s air conditioning system. In fact, incident solar radiation can escape to the exterior through the transparent envelope, which cannot be ignored in buildings with glass curtain walls. This will cause changes in solar heat gain, so the solar heat gain coefficient (SHGC) needs to be corrected. In this paper, the heat transfer process of solar radiation in window shading systems is analyzed, and an amended calculation model for the SHGC is established. Multiple forms of windows and shading systems are selected and their SHGC-amended factor for rooms with different orientations under different standard calculation conditions in various countries is calculated. As the number of glass layers increases, the transmittance of the window gradually decreases, the reflectance and absorbance gradually increase, and the SHGC value decreases. The SHGC-amended factor decreases with an increasing escape rate, and the two can be approximated as a linear correlation. The weakening effect of shading on the solar heat gain of the buildings is overestimated. The SHGC-amended factor proposed in this paper can calculate building solar heat gain more accurately. Full article

The paper deals with selected thermal properties of a small building that was built during the international student competition Solar Decathlon 2021/2022 and is now part of the Living Lab in Wuppertal. It summarizes the essential information about the overall design of this wooden building with construction and technologies corresponding to the passive building standard. Built-in sensors and other equipment enable long-term monitoring of thermal parameters. Part of the information comes from the building operation control system. The thermal transmittance value for the perimeter wall matches calculated expectation well, even from a short period of time and not at an achievable perfectly steady state boundary condition. The (positive) difference between the calculated values and the measured ones did not exceed 0.015 W/(m²K). It was proven that even for such a small building with a very small heat demand, the heat transfer coefficient can be estimated alternatively from a co-heating test (measured electricity power for a fan heater) and from energy delivered to underfloor heating (calorimeter in heating system). Differences among both measurement types and calculation matched in the range ± 10%. In the last section, the dynamic response test is briefly described. The measured indoor air temperature curves under periodic dynamic loads (use of fan heater) are compared with the simulation results. The simulation model working with lumped parameters for each element of the building envelope was able to replicate the measured situation well, while its use does not require special knowledge of the user. In the studied case, the differences between measured and simulated air temperatures were less than 1 Kelvin if the first two to three days of the test period are ignored due to large thermal inertia. Finally, the measurement campaign program for the next period is outlined. Full article

This paper investigates the optimization of insulation thickness with respect to the integration of renewable energy systems in residential buildings in order to improve energy efficiency, maximize the contribution of renewables and reduce life cycle costs. Using the DesignBuilder and EnergyPlus software, this study models a representative two-story residential building located in Athens, Greece. The building envelope features extruded polystyrene thermal insulation and windows with unplasticized polyvinyl chloride frames and low-e glazing. Six scenarios with hybrid renewable energy systems are analyzed, including air- and ground-source heat pumps, solar thermal systems and a biomass fired boiler, so as to assess energy consumption, economic feasibility and internal air temperature conditions. A Pareto-fronts-based optimization algorithm is applied to determine the optimal combination of insulation thicknesses for the walls, the roof and the floor, focusing on minimizing the life cycle cost and maximizing the percentage of renewable energy utilized. The results demonstrate that scenarios involving biomass boilers and solar thermal systems, both for heating and cooling, when combined with reasonable thermal protection, can effectively meet the recent European Union’s directive’s goal, with renewable energy systems contributing more than 50% of the total energy requirements, whilst maintaining acceptable internal air temperature conditions and having a life cycle cost lower than contemporary conventional buildings. Full article