This study experimentally examines how air-layer thickness in a dynamic PCM-enhanced wall affects summer thermal performance and identifies the best configuration for regulation. Five configurations were tested, including a static PCM wall and four dynamic PCM systems with different air layer thicknesses (0, 1, 3, 5, and 7 cm). Experimental results indicate that the air layer thickness has a significant impact on temperature amplitude reduction and heat flux variation in the dynamic PCM system. Key performance metrics-interior surface temperature fluctuations, peak temperature delay, heat flux changes, and total heat load-were measured and compared to the static case. The results reveal that the 5 cm air layer provides the greatest benefits: a 62.8% decrease in interior surface temperature swings and a 1.25-h delay in peak temperature compared to the static PCM; a 53.3% reduction in interior heat flux fluctuations; and the lowest heat gain at 9.95 kJ, which corresponds to a 70.1% decrease in total wall heat load. These findings highlight the critical role of air-layer design in dynamic PCM systems and provide data-driven guidelines for adaptive envelope solutions in warm climates.

Hemp concrete is a sustainable bio-based material whose low mechanical strength limits its use in construction applications. This study aims to enhance its performance through impregnation with sodium silicate solutions at various concentrations. The results demonstrate a significant improvement in mechanical properties and moisture buffering capacity, while preserving thermal performance. At an optimal concentration of 85%, compressive strength increases by 143%, elastic modulus by 368% and moisture buffering capacity by 44.7%. Furthermore, a finite element model complements the experimental approach and shows good agreement with the measured mechanical properties. Numerical results indicate that the Implicit scheme in Abaqus provides more accurate predictions (1-3% deviation) than the Explicit scheme (11-18% deviation). These findings confirm the potential of sodium silicate-treated hemp concrete for applications in non-load-bearing elements, prefabricated panels and sustainable insulation systems.

Phase change materials (PCMs) are promising materials for building thermal management and energy storage, however, leakage remain major concern. In this study, three different carriers including MOF-808, modified defective MOF-808, and 4.5 mm biochar were investigated for the encapsulation of coconut oil as a bio-based PCM. The MOF materials were synthesized via a solvothermal method, while biochar was prepared through grinding and sieving. Shape stabilized phase change materials (SSPCMs) were prepared using a vacuum impregnation technique. The prepared samples were characterized using SEM, BET, PXRD, FTIR, XPS, TGA, DSC, and leakage tests to evaluate their morphological, chemical, and thermal properties. Results show that all prepared SSPCM samples exhibit good chemical stability with successful impregnation of PCM within the carriers. However, SSPCM/Biochar demonstrates better thermal stability and performance, with a higher latent heat capacity of 66.08 J/g, improved ability to eliminate leakage for up to 1 h, and the least leakage signs over 24 h of continuous heating at 60 °C. These results show that biochar can be a more effective carrier for encapsulating coconut oil PCM compared to the proposed MOF materials, offering strong potential for sustainable building thermal energy storage applications.

The development of new low-environmental impact materials is part of sustainable development objectives and offers an interesting alternative to promote building hygrothermal comfort. Raw earth combined with biomass-derived materials is currently gaining strong attention today as they are low-environmental impact materials that also contribute significantly to improving the building hygrothermal performance and comfort. This study aims to develop new raw earth/hemp composites with low hemp shiv content to improve their hygrothermal properties when used as sustainable building materials. The hygrothermal properties of raw earth composites were analyzed including moisture buffer value, water vapor permeability, moisture sorption isotherms, and thermal conductivity. The mechanical properties were also investigated. The moisture buffer capacity result is increased with the hemp shiv content and it exhibits an “excellent” category, from 2.65 g/(m2

Phase change material (PCM) offers promising potential for enhancing the hygrothermal performance of building envelopes. This study proposes a dynamic integration method of PCM within a biomaterial-based concrete wall, aiming to optimize both thermal and moisture regulation in buildings. A numerical investigation is conducted on five wall configurations, with a focus on evaluating the dynamic PCM system. The results show the dynamic PCM wall’s superior performance, achieving temperature fluctuation reductions of 62.5 % and partial vapor pressure reductions of 63.2 % during summer, alongside significant winter improvements of 16.1 % and 6.3 %, respectively. Furthermore, a multi-objective optimization method to minimize the cost and energy consumption of the dynamic system is applied, obtaining the most balanced solution for different climate conditions, as well as demonstrating that a thinner exterior wall layer is preferred for producing lower energy consumption and wall cost. In addition, a long-term assessment further identified interstitial condensation and mold growth risks, particularly in humid climates. Overall, this work highlights the advantages of dynamically integrated PCM systems in biomaterial walls, offering a viable path toward energy-efficient and resilient building envelope designs.

The cooling of PV panel by water flowing on its front face was investigated in this work. This study proposes explicit correlations that calculate the operating temperature of the water-cooled PV panel. To do this, two thermal and electrical models were developed. The thermal model is based on thermal balances carried out on each layer (Glass, silicon and tedlar) of the PV panel. This led to coupled equations that were solved by the CFD calculation code (Ansys Fluent). The operating temperature of the PV panel in uncooled and water-cooled situations was then determined. However, the single-diode electrical model was adapted to evaluate the electrical efficiency from the current and voltage intensities delivered by the PV panel for each situation. Both models were then validated against data provided by an experimental setup. Simulations were then carried out over several days. They show that the average efficiency improvement of the water-cooled PV panel was about 11.5% during a day. Then, for various operating conditions of solar radiation, air temperature, wind speed, water temperature and flow rate, we established correlations that evaluate the operating temperature of the water-cooled PV panel.

An experimental setup was developed, incorporating a monitored DualSun® photovoltaic–thermal (PV/T) panel and a weather station to continuously record real-time climatic conditions. This setup enables an hour-by-hour comparison between the actual performance observed under real-world conditions and the predictions generated by the thermal model. The generated dataset was used to evaluate a thermal model derived from the literature, comparing its predictions with measured data. The model adopts a quasi-steady-state, one-dimensional approach based on heat balance equations applied to both the photovoltaic cells and the heat transfer fluid. Conducted during the summer of 2022, the experiment provides valuable insights into the accuracy of the literature-based thermal model under summer meteorological conditions. The results show a good correlation between the experimental data and the model’s predictions. The average deviation observed for the outlet fluid temperature is 0.1 °C during the day and 1.3 °C at night. Consequently, the findings underscore the model’s effectiveness for evaluating daytime performance, while also pointing out its limitations for nighttime predictions, especially when hybrid PV/T collectors are used for applications such as nighttime free cooling.

The mechanism of fluid and heat transmission within materials with complex porous structures has not yet been fully explored and understood using basic analytical techniques. Therefore, the lack of advanced equipment and techniques has left an important knowledge gap in explaining the complex mechanisms of fluid motion and heat transfer in complex porous structures. This review provides an overview of how image analysis and processing techniques allow insight into the complex and heterogeneous porous structure of materials and explains the mechanism of heat and mass transfer in these complex porous materials in 3D and 4D observation in different directions. Accordingly, it provides interesting results related to the evaluation of microporous properties of complex porous materials including porosity, distribution and size of pores, distribution and orientation of fibers, tortuosity and mechanism of cracking, and destruction of the porous materials under mechanical tests. It also explains the mechanism of liquid transport in porous materials through 3D/4D observation thanks to image processing techniques. Therefore, this review has completed some limited knowledge in microstructural analysis and helped to understand the physical phenomena of liquid transfer in complex porous materials that were not fully exploited by experimental or simulation work. The paper also provides useful data for physical model simulation of imbibition and drying porous materials.

Integrating phase change materials (PCM) into building envelopes has shown promises in reducing building heat load and shifting peak energy demands. However, traditional passive (static) PCM systems have limitations, including inefficient use of latent heat and missed opportunities for outdoor free cooling and heating, as fixed thermal insulation between the PCM and environment restricts the thermal transition. In order to enhance the utilization of the PCM and maximize free cooling and heating for interior thermal comfort, this study introduces a dynamic strategy for moving PCM (DSMPCM) integrated in building walls. This method allows the PCM layer to shift position within the envelope by compressing an air layer, depending on weather conditions. In this study, we compared the dynamic system’s performance with static PCM wall and PCM-absent wall, demonstrating the DSMPCM’s better performance in both summer and winter, where the monthly reduction in heat gain and heat loss are from 135.53% to 535.73% and from 2.92% to 58.76%, respectively. Also, the study identifies optimal PCM key thermal properties, air layer, and wall thicknesses under various climates. Additionally, we explored control strategy optimization to minimize envelope heat loads. These results confirm that properly configuring building envelope properties makes dynamic PCM integration a feasible and effective solution for energy-efficient and sustainable building designs.

Passively integrating phase change material into the walls to enhance the thermal performance of the building has been a promising solution in recent years. As the PCM has a high latent heat capacity, it leads to damping the high variations of temperature and provides an obvious benefit in energy saving and indoor comfort. However, the traditional passive integration method of the PCM limited the utilization of the PCM. The thermal resistance between the PCM and the indoors restrains the thermal response of the PCM, and it between the PCM and the outdoors reduces the impact of outdoor heating or cooling on the PCM. In this study, a dynamic PCM integration in the building envelope method was proposed and experimentally investigated. A PCM layer and an air layer were combined to be integrated into the wall assembly, which allows the position of the PCM layer and the air layer could be changed to adjust the thermal resistance (air layer) between the PCM and indoors and outdoors. The results showed that this dynamic method can dramatically reduce the indoor temperature and the heat flux across the interior surface of the wall. Compared to the envelope with only static PCM layer configurations, the dynamic PCM provided a reduction of 9.1 % in the indoor average temperature and a reduction of 116.0 % in the peak heat flux during the experiment's three days, as well as the dynamic PCM, exploited more latent heat than the other static configurations. Considering the energy performance, the dynamic integration of PCM showed a 100 % reduction in heat gain through the interior surface compared to the envelope with only a static PCM layer under summer conditions.

This study focuses on the improvement of the thermal stability and flame-retardant performance of polyurethane (PU) foam by using effective flame-retardant additives and nano silica (nSiO2) particles from rice husk. The addition of non-halogen flame retardants (FRs) including aluminum trihydroxide (ATH), triphenyl phosphate (TPP), and diammonium phosphate (DAP) leads to markedly enhanced thermal stability and fire resistance of the PU/nSiO2/FRs nanocomposites, resulting in achieving UL-94 HB standard. In particular, the nanocomposites met the UL-94 V-0 criteria thanks to the inclusion of DAP at 25 phr. The LOI value of the nanocomposites reached 26% which is much higher than that of PU/nSiO2 nanocomposite, about 20%. In order to further understand the fire-proof mechanism, the residue char layer remaining of the PU/nSiO2/FRs nanocomposites after being burned was also investigated by scanning electron microscopy (SEM) and Fourier transform infrared (FTIR). In addition, the microstructure, thermal stability, thermal conductivity, and mechanical properties of nanocomposites were also evaluated in this study.

Phase change material (PCM) and hygroscopic material (HM) in building walls are promising passive technologies for temperature and humidity regulation, respectively. Integrating the two materials allows for hygrothermal environment regulation and energy savings. However, the joint effect of the temperature dependence of the HM's hygroscopic properties and the location dependence of the PCM's thermal properties has not been mentioned or demonstrated. This study experimentally assessed the hygrothermal and energy performance of a shell enclosed by a PCM-HM wall. Different wall scenarios were proposed to study the effect of the HM, PCM, and PCM's location. The results highlighted the dominance of temperature and the significance of the PCM on performance. For PCM walls, the thermal and hygric inertia were enhanced, the characteristic times of temperature/relative humidity were increased, and the variation was dampened. Under a sinusoidally varying climate, the peak temperature, thermal load, and fluctuations in temperature, relative humidity, and vapor pressure were reduced, and the peak temperature was delayed. Additionally, the repositioning of the PCM further improved the performance. When the PCM was repositioned from the outside to the middle, the temperature, relative humidity, vapor pressure fluctuations, and thermal load were reduced by 25.0 %, 45.8 %, 54.6 %, and 33.1 %, respectively, in warm to hot climates, and by 12.5 %, 63.6 %, 41.9 %, and 66.0 %, respectively, in cold to temperate climates. The PCM properties are important as the PCM in the PCM-middle wall has a higher melt fraction in the solid-liquid state, which utilizes more PCM latent heat energy and improves wall performance.

This paper deals with the experimental investigation of hygrothermal behavior of wooden-frame building envelope. The experiment was based on in-situ monitoring of a full size experimental monozone house built at the University of Lorraine. Variations in temperature and relative humidity inside and outside the envelope were logged simultaneously with local meteorological data. Results showed the high coupling between temperature and relative humidity variations within the envelope materials. An overall hygrothermal response of the wall highlighted an interesting hygrothermal dynamic behavior of the envelope which may contribute to mitigate variations of relative humidity inside the building. Nevertheless, relative humidity evolves within a range of values that can lead to mold growth at a certain position which may alter wooden envelope life.

This paper focuses on the FE analysis of the mechanical behavior of glued composite fiber-reinforced polymer (FRP) rods into glulam timber, using a 3D-continuum damage mechanics. The application of FRP to the glulam timber beams, despite the fact of limited investigations to date, offers an interesting and economic solution for strengthening in timber construction. In particular, the use of glued-in FRP rods for timber connections instead of steel is of great interest, due to the improved durability of the joint systems compared to their equivalent counterparts made of steel rods. For pull-out tests, the estimation of the mechanical response of glued FRP rods into glulam timber is very complex because of the combination of the three different materials: FRP rods, epoxy resin and glulam timber as well as the complexity of the expected brittle modes of failure of the timber. On the other hand, the existing prescriptive approaches (standard design codes) did not cover all the modes of failure expected within timber material and their predictivity is highly depending on the loading direction and on the rod material. There is, therefore, still a need to establish a general and predictive FE model to simulate accurately and cost-effectively the glued-in rod timber connections. In this study, a FE model combining 3D continuum damage mechanics (CDM) and cohesive zone modeling approaches is presented and its effectiveness was verified by comparison to experimental results available in the literature.

Phase change materials (PCMs) have high thermal inertia while hygroscopic materials have high hygric inertia. However, few studies have integrated the two materials and considered both hygrothermal behavior and energy performance. This study proposed a novel multilayer building envelope integrated by PCM and bio-based hygroscopic material (hemp concrete) to utilize the advantages of both materials. Four envelope configurations were experimental studied based on the presence and location of the PCM to study the effect of PCM and its location on the hygrothermal behavior and the energy performance of the integrated envelope. The results demonstrated the benefits of PCM in reducing the temperature/relative humidity (T/RH) amplitude and energy consumption as well as delaying the peak T of the envelope. Placement of the PCM in the middle of the envelope was recommended, with the PCM kept in a partially melted state. Compared to the configuration without PCM, the T/RH amplitude and energy consumption were reduced by 50%/60% and 15.3%, respectively, and the peak T was delayed by 70.4%. The PCM placed on the outdoor side had the highest efficiency and energy participation, but it absorbed the most heat and was prone to overmelting. The envelope with PCM placed on the indoor side lost the benefit of regulating RH. This study provides a reference for multilayer envelopes composed of PCMs and hygroscopic materials and dedicated to T/RH regulation.

Phase Change Materials (PCMs) have high thermal inertia, and hemp concrete (HC), a bio-based concrete, has strong hygroscopic behavior. In previous studies, PCM has been extensively combined with many materials, however, most of these studies focused on thermal properties while neglecting hygroscopic aspects. In this study, the two materials have been combined into a building envelope and the related hygrothermal properties have been studied. In particular, numerical studies have been performed to investigate the temperature and relative humidity behavior inside the HC, and the effect of adding PCM on the hygrothermal behavior of the HC. The results show that there is a high coupling between temperature and relative humidity inside the HC, since the relative humidity changes on the second and third days are different, with values of 8% and 4%, respectively. Also, the variation of relative humidity with temperature indicates the dominant influence of temperature on relative humidity variation. With the presence of PCM, the temperature variation inside the HC is damped due to the high thermal inertia of the PCM, which also leads to suppression of moisture evaporation and thus damping of relative humidity variation. On the second and third days, the temperature changes at the central position are reduced by 4.6% and 5.1%, compared to the quarter position. For the relative humidity change, the reductions are 5.3% and 5.4% on the second and third days, respectively. Therefore, PCM, with high thermal inertia, acts as a temperature damper and has the potential to increase the moisture buffering capacity inside the HC. This makes it possible for such a combined envelope to have both thermal and hygric inertia.

Bio-based materials have strong hygrothermal behavior and phase change materials (PCMs) have high thermal inertia, but they have usually been studied separately in most research. In this paper, the hygrothermal behavior of a multilayer building envelope integrating hemp lime concrete (HLC) and PCM was investigated at experimental level. The envelope was flanked by a climate chamber and the laboratory ambient to imitate the outdoor and indoor environments, respectively. Four envelope configurations comprising a reference (without PCM) and three configurations with PCM (PCM placed on the outdoor and indoor side, in the middle of the envelope) were considered in order to study the effect of PCM and its position on the hygrothermal behavior of the envelope. The results showed that the PCM had a significant effect on the hygrothermal behavior of HLC, based on the high coupling between temperature and relative humidity. The characteristic time was considered to quantitatively evaluate temperature and relative humidity trends, and their value was increased with the participation of PCM. Moreover, PCM increased the heat store/release capacity linearly with its position. The closer the PCM was to the outdoor, the higher the heat store/release capacity and the lower the heating/cooling load from the envelope to the indoor environment. These phenomena were closely related to the PCM's temperature distribution and its corresponding specific heat capacity. Therefore, due to the envelope's thermal and hygric inertia on the indoor environment and the building's energy saving potential, it was recommended that the PCM be placed close to the outdoor side.