Thermal Performance Of Buildings Research Articles

Characterization and Energy Performance of WO3 Doped and Undoped Photochromic Films

When exposed to light sources, photochromic (PC) materials change their optical properties and can lessen the transmission of UV and infrared radiation. This results in optimal thermal comfort and a pleasing visual contrast between the internal and external settings. This study uses computer modeling to analyze the annual energy usage in a home with natural ventilation in order to compare the effectiveness of photochromic films with commercial glass. The study is carried out using the EnergyPlus program in the cities of São Carlos and Cuiabá ‐ Brazil. Experiments and numerical simulations with data from doped and undoped tungsten trioxide (WO3) PC films are used in the study. Given the rise in energy usage and the pursuit of thermal comfort, this method is essential for assessing the thermal performance of buildings. Evaluations included a comparison of air conditioner performance and energy savings analysis, which leads to a noteworthy annual reduction in energy usage of up to 216.55 kWh and a 40% improvement in visual comfort. It is determined that PC film's dynamic behavior is the best option for comfort in terms of heat, illumination, and visual comfort.

Properties of foam concrete containing phase change material impregnated pumice

Energy consumption rises as a result of numerous electrical devices used to maintain thermal comfort of interior building areas. Using building materials with low thermal conductivity and density as well as an effective thermal energy storage plan can help to mitigate this. In order to enhance thermal performance of building, phase change material (PCM) was incorporated to foam concrete mixture in this study. Capric acid (CA)-palmitic acid (PA) eutectic mixture was prepared and impregnated with pumice (50 % by weight), a light and porous material. DSC results indicated that pumice/CA-PA composite exhibited a melting temperature of 22.84˚C and a freezing temperature of 20.85˚C, with corresponding enthalpy values for melting and freezing determined to be 85.4 J/g and 85.1 J/g, respectively. TGA analyses demonstrated that operational temperature of pumice/CA-PA composite was significantly below its thermal degradation temperature (194˚C). The prepared pumice/CA-PA composites were replaced with silica aggregate at different rates and incorporated in foam concrete mixture. Porosity and water absorption values rose as pumice/PCM content increased, yet there was a 7.2–41.1 % drop in dry unit weight when compared to reference. Compressive strength also showed a linear decrease and the lowest compressive strength value was recorded as 4.71 MPa in the presence of 40 % pumice/PCM. Thermal conductivity dropped from 0.487 W/mK to 0.167 W/mK, suggesting that foam concrete samples that were produced are all suitable as insulation materials. In peak solar radiation hours, PCM-impregnated pumice foam concrete (PFC) provided about 11.8 % and 8.72 % surface and room center temperatures compared to that of the reference in maximum case. PFC with PCM provided 6.54 % warmer surface temperature in cold weather. PFC-PCM can provide a cooler indoor temperature during peak temperature hours. Therefore, it may have a great potential to decrease the cooling load of a building.

Enhancing Thermal and Daylight Performance of Historic Buildings with Passive Modifications; A Tropical Case Study

Historical buildings worldwide hold immense potential for adaptive reuse within the framework of the circular economy, a concept gaining traction in the building construction industry for its role in reducing carbon emissions. Many of these structures boast passive building design strategies, which inherently lower energy demands. Among these, thermal mass and daylight harvesting emerge as pivotal strategies for achieving indoor thermal and visual comfort, respectively. However, with the advent of significant climate change and evolving built environments, the efficacy of these historical passive strategies is subject to debate. This study focuses on a residential building constructed in the 17th century by Dutch settlers in Galle, Sri Lanka, serving as a case study. The research targets improvements in both thermal and visual comfort. Thermal performance analysis was conducted through air temperature measurements, revealing a notable 3-hour time lag and a 2.5°C reduction in peak air temperature during the day. Conversely, nighttime measurements indicated a rise in indoor temperature compared to ambient conditions. Using Design Builder software, the building was modelled to assess its daylighting conditions. Drawing upon thermodynamic principles and daylight harvesting techniques, the study proposes building envelope interventions and ventilation strategies to address nighttime overheating and enhance daylight utilization. The results demonstrate that these modifications can potentially reduce nighttime heat by 2-3°C, while also decreasing the energy requirement for lighting comfort from 51.10 kWh/m² per annum to 44.84 kWh/m² per annum. This research showcases the effectiveness of judiciously implemented interventions in historical buildings, illustrating tangible improvements in both thermal/visual performance and energy efficiency. Leveraging inherent qualities of historical structures and integrating modern design strategies to these buildings can play a vital role in sustainable urban development and energy conservation efforts.

A simplified modeling method for studying the thermal performance of buildings with vertical greening systems

Vertical greening systems (VGS) are considered an effective strategy to enhance the insulation performance of the building envelope. Existing methods predicting the performance of this strategy usually require a combination of mathematical modeling and building performance simulation, hence difficult for practical use. To simplify this work, this study has proposed a prediction method requiring building simulation only, by considering VGS as a shading component in the simulation work. To compare its performance, a model using conventional methods has also been proposed. A further simplification by neglecting the impact of transpiration has been investigated as well. To justify the implementation of the new method, it has been used to optimize the design of VGS for buildings located in the hot summer and cold winter areas in China. The validation result confirmed the accuracies of both methods, with the simpler method giving an insignificant lower accuracy than the conventional method, which can be compensated by its simpler prediction procedure. The implementation justification showed that for buildings in the HSCW area, VGS is suggested to be installed on the west facade, with a leaf area index of 4. This can help to reduce the heat transfer of the wall by 56.6%.

Development and performance evaluation of active insulation systems using solid-state thermal switches

Traditional building envelopes have passive insulation systems that cannot respond to dynamic changes in the environment. An Active Insulation System (AIS) consists of Active Insulation Materials (AIMs) that dynamically vary the thermal conductivity of the insulation system. Several researchers have evaluated the impact of AIS on building thermal and energy performance by using simulation tools. Up to 70% savings in annual heating and cooling energy and significant reductions in peak demand have been predicted for some climates with wall systems employing AIS. However, materials and assembly development still need a cost-effective product that achieves the required performance. In this study, we present the process of developing an AIS that we will install in a test hut for its performance evaluation. Minimum performance criteria of the AIS system are developed based on R-low/R-high ratio, required time and efficiency to switch states, and cost estimates. The following steps during this study are creating the concept to meet the requirements, predicting the performance via simulations, developing the experimental setup for bench-scale testing, and finally, constructing a full-scale wall assembly and monitoring the performance when exposed to environmental chamber tests. The selected approach uses off-the-shelf products to create an AIS that can switch R-value between 0.98 ft2·°F·h/BTU (0.173 m2·K/W) and 5.81 ft2·°F·h/BTU (1.02 m2·K/W) and have a switching time of less than one minute between R-high and R-low.

Thermoelectric active window frame: Constructive integration and preheating analysis

Building heating and cooling systems using thermoelectricity appear to be a feasible alternative, as it presents several features including versatility and high reliance. While most applications of thermoelectricity in buildings are found in wall systems, window integration shows excellent potential for enhancing the thermal performance of buildings at the façade level, compensating heat losses that take place in windows. Combining energy efficient ventilation with heat recovery leads to a significant reduction of the required energy, keeping desired comfort conditions inside buildings. Thus, the following study presents the design of an active window frame with an integrated thermoelectric system, attaining two functions: pre-heating the supply air, while simultaneously recovering the waste heat energy from exhaust air. Two full-scale prototypes were built, each featuring a different airflow pattern, and preliminary tests for heating mode were carried out under laboratory conditions. The results revealed a similar performance comparing both prototypes, achieving a COP ranging 1.56 to 2.71 for prototype A, while prototype B ranged from 1.62 to 2.65. The results showcase superior heating efficiency compared to a previous experiments conducted by the research group, where a maximum COP of 1.91 was achieved. From a building perspective, wider adoption of thermoelectricity applied to thermal conditioning is hindered by lack of suitable products for architectural integration. Therefore, the system's innovation stems from optimized design, integrated construction, and industrialized production, enhancing energy efficiency in buildings via a compact façade integrated system without space compromise.

Optimizing the thermal performance of residential buildings in Jordan

This work investigates the influence of building form, natural ventilation, and window shading passive strategies on the thermal performance and thermal comfort of three residential building forms, namely rectangular, L-shape, and U-shape, in the hot-dry summer in Amman, Jordan. The thermal performance of buildings is studied using indoor air temperature, and the thermal comfort is evaluated according to ASHRAE-55 and Fanger’s models. The buildings’ models are designed using the SketchUp plugin OpenStudio and then plugged into the EnergyPlus simulator. It is obtained that when natural ventilation and shading devices are considered together, the indoor air temperature is notably dropped up to 8.85 °C in the daytime and 12.70 °C at nighttime, which improves the thermal comfort of all building forms. Generally, rectangular building exhibits the best thermal behavior under optimum conditions. U-shape presents the best thermal behavior for the primary conditions, and it records the lowest out-of-comfort percentage time during the day and achieves the highest comfortable percentage after considering the window’s area control.

Modeling of heat gain through green roofs utilizing artificial intelligence techniques

Green roofs have recently been popular in buildings for saving energy. A reliable model is required to include green roofs' role in the thermal performance of buildings. This study applies artificial neural networks (ANN) to estimate the buildings’ heat gain through green roofs. By comparing different ANN architectures (feedforward, recurrent, and cascade), the best model to estimate heat flux from four significant design factors (plant height, leaf area index of plant, soil depth, and overall heat transfer coefficient of support layer) is determined. The relevance test clarifies that the overall heat transfer coefficient of the support layer and the leaf area index of the plant have the highest correlation with the target variable. The modeling results prove that the multilayer perceptron (MLP) neural network with 4-5-1 topology and the logarithm sigmoid and liner activation functions in hidden and output layers has the best accuracy for the given task. This model predicts 2700 literature data with the regression coefficient = 0.9999, mean absolute errors = 0.025, and root mean squared errors = 0.035. Our topology-engineered MLP can analyze the effect of design factors on the heat flux through green roofs and help quickly determine its impact on building thermal performance.

Experimental analysis of building envelope integrating phase change material and cool paint under a real environment in autumn

The application of phase change material (PCM) and cool paint (CP) to building envelope is one of the effective solutions to improve thermal comfort of passive buildings. Therefore, the thermal performance of buildings in Hefei, China in autumn is compared and analyzed by integrating PCM and CP into the building envelope. According to the comprehensive analysis of indoor thermal environment and the ability to maintain indoor thermal comfort, it is concluded that the combined application of PCM and CP is better than the application of PCM or CP alone. And the combination of PCM and CP laid on the south wall and roof respectively is the best. It is more suitable for commercial buildings, which can prolong indoor air temperature (Ti) in the thermal comfort zone for more than 10 h during the day. The combination of PCM and CP laid on the roof can prolong Ti in the thermal comfort zone for more than 8.05 h, which is more suitable for residential buildings. The purpose is to explore the best combination mode of residential and commercial buildings according to the characteristics of temperature change and building types (according to people's main use time) in the real environment.

A comparative life cycle assessment of building sustainability across typical European building geometries

In recent years, significant progress has been made in the sustainability assessment of building materials and buildings. The introduction of Environmental Product Declarations (EPDs), the development of Level(s), and the release of relevant series of standards have helped to improve the sustainability of buildings. However, a research question that remains unresolved is the lack of information related to the comparison of the sustainability performance of building units across Europe and the significance of conducting such research. This study addressed this question by implementing a comparative whole-building Life Cycle Assessment (LCA) across buildings in Europe. The study emphasizes the necessity of considering typical building geometries and thermal performance of buildings across Europe and introduces six typical building geometries for three different European clusters (northern-western, central-eastern, southern cluster). The results of this study revealed that the sustainability performance of buildings is not similar across the EU and that cost-optimal minimum thermal performance requirements for building structures have a significant impact on their environmental performance. Particularly, single-family houses in Central and Eastern Europe are responsible for 324.42 kgCO2e/m2. Contrary to this, Northern and Western European single-family buildings have the lowest environmental impact with 268.97 kgCO2e/m2. Multifamily houses in Southern Europe are responsible for 321.82 kgCO2e/m2, in Northern and Western Europe the environmental impact is 275.37 kgCO2e/m2. The outcome of this study is significant for the scientific community involved in assessing the sustainability of buildings in Europe, as it provides valuable insights into their environmental performance, considering the energy efficiency and sustainability aspects of buildings. The study's findings should be considered when setting minimum LCA-related requirements, in view of the provisions of the new EU policies expressed in the Energy Performance of Buildings Directive (EPBD) recast for defining the Global Warming Potential (GWP) of new buildings.

Contribution of advanced windows and façades to buildings decarbonization: A comprehensive review

On a global level the building sector consumes about 45.00% of energy consumption, contributes about 40.00% to emission, uses 30.00% of water and impacts the environment by generating 30.00% of waste. Although windows are important components of a building that provide natural lighting and ventilation and establish necessary contact with the external environment necessary for healthy indoor ambient, they permit entry of undesirable solar heat in summer and allow escaping heat from the indoor ambient in cold seasons, which aggravate the building needs for energy and increase its contribution to atmospheric emissions. The present investigation provides a review on research, development, and applications of advanced windows in the building sector. The introduction highlights the importance and contribution of advanced glazing technology to improving energy, comfort, and thermal performance of buildings. The review includes natural illumination and ventilation, thermal comfort and discusses the effects of window to wall ratio on natural illumination and ventilation of windows and façades. The review also covers recent developments in glazed windows and façades including performance enhancements by using reflective solar films, vacuum glazing, windows with filling materials, windows with water flow, window with phase change material, window with stagnant inert gas filling, ventilated windows and façades and windows with aerogel. A special section was also included on smart glazing for windows and façades showing the new tendencies and applications in the building industry. Since commercial programs and open access codes are handy tools for simulation and performance calculations a section is dedicated to these codes. The conclusion section contains the most relevant conclusion of the review as well as future trends in research and developments in the area. The topics included in this review can be helpful for experienced and young researchers, practicing engineers and general readers interested in windows and façades.

How to improve the thermal performance of buildings with one simulation run? The heat exchange index applied to hot climates

Improvements in the thermal and energy performance of buildings usually involves techniques with high computational costs, such as multi-objective optimization and parametric simulation. However, sometimes, achieving the optimal case is not desirable, though only the refinement of thermal performance. Hence, methods that enable this analysis are helpful for designers and researchers. Then, this study proposed a framework based on the Heat Exchange Index to assist thermal performance analysis of buildings. The framework consists of two phases and begins by exploring air and surface heat balance derived from the base case building simulation. This analysis is based on the Heat Exchange Index, an index developed in this work, and its result indicates the impact of each heat exchange on the thermal performance. The next phase is the improvement, where strategies are defined and implemented, and the thermal performance of the improved case is evaluated against the base case. A single-family house was modeled using EnergyPlus to demonstrate the framework application. Results showed that the Heat Exchange Index could be used to enhance the thermal performance of buildings since the strategies adopted in the base case increased its thermal autonomy and decreased thermal load.

Development of ReShadS, a climate-responsive shading system: Conception, design, fabrication, and small-scale testing

Integrating computational technologies to produce dynamic and intelligent architecture that can enhance building thermal performance and meet users' requirements and routines is broadly classified as responsive architecture. This seems to be a viable solution for façades, reducing energy demand during the building operational phase. However, scientific content regarding responsive components' fabrication, operation, and performance evaluation is not yet consolidated. This paper comprehensively presents the design and fabrication processes of a low-cost responsive shading system prototype, accounting for materials' characterization, software, responsive functionality, and its performance evaluation regarding thermal and illuminance management. The analysis is based on the Adaptive Comfort Model and Useful Daylight Illuminance parameters. Preliminary results indicate the system's feasibility in managing temperature and illuminance within the comfort zone by 58 % and 82 % of data points, respectively. The resulting prototype and the responsive management strategy contribute to the emerging responsive architecture field toward reducing building energy consumption.

Multiple regional climate model projections to assess building thermal performance in Brazil: Understanding the uncertainty

Understanding the trends and uncertainties in Building Energy Simulation (BES) performance indicators under future climate conditions is crucial for mitigating issues such as overheating and power outages. To address this, we generated a set of weather files for all 27 state capitals in Brazil, considering six climate model projections (three General Circulation Models as driving models and two nested Regional Climate Models) and two distinct emission scenarios from the CORDEX project. We analyzed the variability in climatic variables and subsequently performed BES on a representative Brazilian social housing unit to evaluate its impact on the performance indicators outcomes. Consistent with previous studies, a substantial increase in cooling-related demands was observed in the more pessimistic scenario (RCP8.5) and mild increases in the more optimistic scenario (RCP2.6), with a trend toward stabilization after 2050. Regarding uncertainties, we found higher Relative Standard Deviation (RSD) values for the cooling degree hours indicator. The capitals in the Central-West, Southeast, and South regions exhibited greater uncertainty regarding temperature indicators, whereas the irradiation parameters displayed higher uncertainties in the Northeast region. For the BES outcomes, RSD values as high as 19.9% were found for cooling load values. It was also demonstrated that locations, periods, and scenarios exhibit different extreme climate model projections. Ideally, employing an ensemble of weather files developed from other models would help assess associated uncertainties in the building performance indicators.

Statistical Analysis of the Factors influencing the In Situ U-Value of Walls

Building thermal performance testing requires in situ measurement techniques that are well supported and validated by simulation with statistics to improve the accuracy of the results. Local on-site performance of building components is different from the theoretical one, influenced by factors affecting the building's thermal conditions. The current paper reviews the factors influencing the measured U-value results in the heat flux method based on quantitative findings of other studies through regression and correlation statistics. The findings regarding the current status of knowledge are limited to in situ methods without detailed insights of response time, sensitivity analysis, and thermal boundary conditions in the local context. Regression analysis between wall characteristics, time duration, temperature difference, and the measured U-value shows a very strong and statistically significant impact of these variables on the accuracy of the measured U-value of low transmittance walls. The R2 value indicates that three variables can collectively explain 91% of the variance in the measured U-value. There is a linear correlation between the wall characteristics and the measured U-value and a non-linear correlation between the time duration, temperature difference, and the measured U-value. Future work will focus on developing a measurement framework that considers time-dependent variables, dynamic weather, and uncertainty with high accuracy for different boundary conditions.

Thermal Behaviour Assessment of Brick Utilizing Plastic Waste for Enhanced Insulation Properties

Plastic waste, particularly hazardous types such as high-density polyethylene (HDPE) and Polyethylene terephthalate (PTE), is a critical problem in today’s world. Recycling plastic waste to produce new materials like concrete or mortar is an effective disposal method. One such solution is adding plastic waste to bricks to create an environmentally friendly and cost-effective option to produce high-strength bricks with thermal and sound insulation properties. The study intends to investigate the feasibility of reusing plastic waste as a mixture in brick production as an eco-friendly alternative to traditional bricks. To compare the thermal performance of buildings made of plastic waste bricks and traditional bricks, the researchers digitally created four sample bricks, each containing 0%, 5%, 10%, and 15% HDPE. The thermal performance of the brick-filled plastic bottle walls was then measured on-site at a real-time recording using a chamber and tested with the thermocouples connected to a data logger - T08 software. The results showed that 10% and 15% plastic waste brick composition had higher insulation properties with the difference between internal and external air temperature average of 6°C. The lower the external air temperature with the least amount of plastic waste recorded the lowest temperature difference average of 1°C. At the external temperature of 30°C, the 0% and 5% plastic waste bricks possessed the greater internal temperature, likely due to the external air temperature flow in the box’s confined space. Thus, further research and experimentation are recommended to investigate the thermal conductivity of plastic waste bricks and their correlation with the insulation properties of the material samples.Keywords: environment, construction, plastic waste, thermal performance

Performance analysis of a novel phase-change wall of wood structure coupled with sky-radiation cooling

The integration of phase-change materials (PCM) into building enclosures can effectively improve the thermal performance of buildings. In this study, a novel phase-change wall of a wood structure with embedded capillaries that can utilize sky-radiation cooling is proposed to reduce energy consumption. The performance of the proposed wall was experimentally investigated and compared to that of an ordinary wood-structured wall under summer conditions. The results show that the proposed wall can significantly reduce the internal temperature of the wallboard and indoor air temperature. Compared with a traditional room with ordinary wood structure walls, the room using the PCM wallboard results in a more stable temperature fluctuation. Furthermore, the load from the east-oriented wall was reduced by 15.63%, the optimum decrement factor was 0.44, and the intensity of thermal discomfort was reduced in all directions. Therefore, the proposed wall has great application potential for reducing energy consumption and improving thermal comfort.

Thermo-structural analysis and design for multi-functional membrane roofs of airport terminals

The utilization of large-span membrane structures in airport terminals has attracted considerable attention due to their excellent building aesthetics, reasonable structural behavior and multi-functional applications. Integrating structure and function is useful to improve thermal performance of such buildings. This study focuses on a scaled two-layer membrane roof in accordance with a newly-built aerogel-membrane airport roof and investigates the dynamic building thermal performance. The two-layer membrane roof is composed of an outer membrane layer as structural element, an air gap for ventilation and an inner membrane layer integrating aerogel mats. The effects of aerogel thickness, ventilation velocity and gap height are analyzed with multi-physics numerical tools. The structural behavior of the aerogel-membrane roof structure is examined in agreement with the building standards. The comparison between numerical and experimental results on solar irradiance is performed to demonstrate the reliability of numerical results under the typical environmental conditions. The thickness of the aerogel layer and the ventilation velocity are shown to have a significant effect while the air-gap height plays a minor role. A maximum temperature reduction of 4.7 °C demonstrates that using the proposed approach can improve building thermal performance. Moreover, temperature curves with small fluctuations indicate an efficient control of the indoor temperature. Therefore, the thermo-structural analysis method of the multi-functional membrane roofs can guarantee structural safety and facilitate building thermal performance control.

Energy performance analysis of alternative building retrofit interventions for the four climatic zones of Greece

Climatic conditions determine which retrofit strategy can result in a satisfactory improvement of a building's thermal performance. This study systematically investigates alternative retrofit actions, as standalone and in combination, and assesses their energy performance. The retrofit actions include i) insulation on the external walls, ii) the incorporation of phase change material (PCM) on the roof and the increase of the building thermal inertia, iii) a mechanical ventilation system with a summer period operation, and iv) a cool roof coating. The energy analysis concerns a typical two-story family building and the four climatic categories of Greece and is conducted with the INTEMA.building tool, a dynamic energy analysis software developed in Modelica language. The importance of the present study is that it serves as a guideline for the selection of the energetically optimum single retrofit or multiple-retrofit strategy regarding a building's location climatic data, and provides calculations concerning the annual heating and cooling loads, and the corresponding heat pump electricity consumption. The retrofit actions of external wall insulation and PCM roof addition are characterized as more effective in reducing a building's heating energy loads, while the mechanical ventilation system and cool roof coating are more effective in reducing a building's cooling loads. The quadruple retrofit strategy results in the maximum electricity savings for Heraklion (28.01%), Athens (21.15%), and Thessaloniki (16.54%), while the triple retrofit strategy which does not include the cool roof coating, results in the maximum electricity savings for Kastoria (10.79%). Lastly, an economic analysis of the energetically optimum renovation strategies is conducted.

A Qualitative Analysis Using Thermography for Characterization of the Built Environment

The revised Energy Performance of Buildings Directive (EPBD) recognizes nearly zero-energy buildings (nZEB) and building renovation as essential steps in the decarbonization of the built environment. A thorough understanding of existing buildings is a prerequisite for improving their thermal performance and ensuring that interventions are based on pre-existing conditions. This study investigates the use of thermography as a tool for identifying construction solutions and assessing the thermal performance of buildings. Initially, it addresses the benefits and limitations of this technique, as well as some results of a qualitative analysis and standard application of this technology. Specific conditions for capturing images on-site were identified, along with the relevant factors for interpreting thermograms under natural conditions. These images enabled the identification of previous works, changes in buildings, and the use of different materials and construction techniques, thereby contributing to the characterization of buildings. Consequently, they can be used in the diagnostic phase to enhance the accuracy of intervention solutions based on a better understanding of existing conditions.