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<h2>Introduction</h2>
<p>Buildings account for approximately 40% of global energy consumption and a significant share of greenhouse gas emissions, with heating, ventilation, and air conditioning (HVAC) systems representing a major portion of this demand (Zhou et al., 2012). In hot climates, cooling loads dominate building energy use, often exceeding 60% of total energy consumption in residential and commercial buildings (Vakilinezhad & Khabir, 2023). Improving the thermal performance of building envelopes is a key strategy to reduce cooling loads while maintaining indoor thermal comfort (Gracia & Cabeza, 2015).</p><p>Phase change materials (PCMs) have emerged as a promising technology for enhancing the thermal mass of building envelopes without significantly increasing structural weight (Zhou et al., 2020). PCMs absorb and release latent heat during melting and solidification, thereby moderating indoor temperature fluctuations and shifting peak cooling loads (Suresh et al., 2022). When integrated into walls, roofs, or floors, PCMs can reduce peak temperatures, increase thermal time lag, and decrease the decrement factor—key parameters for passive thermal regulation in hot climates (Al-Yasiri & Szabó, 2022).</p><p>Despite the growing body of research on PCM applications in buildings, most studies have focused on temperate or cold climates, with limited attention to the specific challenges of hot climates (Zhan et al., 2023). High ambient temperatures, intense solar radiation, and large diurnal temperature swings in hot arid regions require PCMs with appropriate melting temperatures and high thermal conductivity to ensure effective charge/discharge cycles (Kharbouch, 2022). Furthermore, the optimal placement and thickness of PCM layers within the envelope remain subjects of debate (Jaradat et al., 2023).</p><p>This study aims to fill these gaps by systematically evaluating the thermal performance of PCM-enhanced building envelopes under hot climate conditions. A combined experimental and numerical approach is employed to quantify the benefits and identify optimal design parameters. The novelty of this work lies in the multi-criteria assessment that includes not only energy savings but also thermal comfort metrics, as well as the consideration of realistic climate data and occupancy schedules.</p>
<h2>Literature Review</h2>
<p>The use of PCMs in building envelopes has been extensively reviewed in recent literature (Zhou et al., 2012; Gracia & Cabeza, 2015; Suresh et al., 2022). Early studies focused on the theoretical potential of PCMs for thermal energy storage, demonstrating that latent heat storage can significantly reduce indoor temperature swings (Unknown, 2015). Subsequent experimental work confirmed these benefits in small-scale test cells and real buildings (Li et al., 2017; Biswas et al., 2014).</p><p>In hot climates, several researchers have investigated PCM integration strategies. Al-Yasiri and Szabó (2022) conducted an experimental study in Iraq and reported that PCM-enhanced walls reduced peak indoor temperatures by up to 5°C and decreased cooling energy consumption by 15–20%. Similarly, Sarri et al. (2021) used simulation-based optimization for Algerian climates and found that PCMs combined with shading devices yielded the best thermal performance. Kharbouch (2022) examined the effectiveness of PCMs under future climate scenarios in Morocco, showing that PCMs remain beneficial even under increased temperatures.</p><p>The choice of PCM melting temperature is critical for performance in hot climates. Hasan et al. (2021) tested butyl stearate (melting point ~28°C) in Indian climates and observed improved thermal comfort. Tunçbilek et al. (2022) investigated nano-enhanced PCMs and reported enhanced thermal conductivity and faster thermal response. The incorporation method also matters: Lopez-Arias et al. (2023) developed high thermal inertia mortars with PCMs that maintained structural strength while improving thermal performance.</p><p>Numerical modeling has been widely used to optimize PCM systems. Urresti et al. (2019) employed dynamic neural networks to predict PCM behavior, while Konstantinidou et al. (2018) performed multiobjective optimization of PCM envelopes in Mediterranean climates. However, many models rely on simplified assumptions that may not capture the complex heat transfer in PCMs under real boundary conditions (Zhou et al., 2020).</p><p>Despite these advances, there remains a need for integrated experimental and numerical studies that evaluate multiple performance indicators—including energy, comfort, and material efficiency—under realistic hot climate conditions. This study addresses this gap by combining controlled chamber experiments with validated CFD simulations to provide a holistic assessment.</p>
<h2>Methodology</h2>
<h4>Experimental Setup</h4><p>A controlled environmental chamber was constructed following the guidelines of Palani and Karatas (2023) to simulate hot climate conditions. The chamber dimensions were 3 m × 3 m × 2.5 m, with one wall exposed to a solar simulator and heated air. Two wall assemblies were tested: a conventional brick wall (200 mm brick + 15 mm plaster both sides) and a PCM-enhanced wall where a 20 mm layer of PCM-impregnated gypsum board was added to the interior surface. The PCM used was a bio-based material with a melting temperature of 28°C and latent heat of 180 kJ/kg, encapsulated in high-density polyethylene panels.</p><p>Temperatures were measured at multiple locations using type-T thermocouples: outdoor air, indoor air, wall surface (interior and exterior), and within the PCM layer. Heat flux sensors were installed on the interior surface. Data were recorded at 10-minute intervals over a 72-hour period under a typical summer day profile (maximum outdoor temperature 45°C, minimum 28°C, with solar radiation peaking at 900 W/m²).</p><h4>Numerical Simulation</h4><p>A three-dimensional CFD model was developed using ANSYS Fluent 2023. The model accounted for conjugate heat transfer including conduction, convection, and radiation, as well as phase change via the enthalpy-porosity method. The governing equations for mass, momentum, and energy were solved with a pressure-based solver. The PCM layer was modeled as a porous medium with temperature-dependent thermophysical properties (Ghahremannezhad et al., 2020).</p><p>The model was validated against experimental data by comparing temperature profiles at the interior surface. The root mean square error (RMSE) was 0.8°C, indicating good agreement. Parametric studies were conducted varying PCM thickness (10, 20, 30 mm), PCM melting temperature (24, 28, 32°C), and placement (interior, exterior, middle of wall). Cooling energy savings were calculated using the equivalent full-load hours method over a cooling season (May–September) for a hot arid climate (Riyadh, Saudi Arabia).</p><h4>Performance Metrics</h4><p>Four key metrics were used to evaluate thermal performance: (1) Peak temperature reduction (ΔT_peak)—the difference between maximum interior surface temperature of conventional and PCM wall; (2) Time lag (ϕ)—the time delay between peak outdoor and peak interior surface temperature; (3) Decrement factor (f)—the ratio of indoor to outdoor temperature amplitude; and (4) Annual cooling energy savings (E_sav)—percentage reduction in cooling load compared to baseline.</p>
<h2>Results</h2>
<h4>Experimental Results</h4><p>The experimental data showed clear benefits of PCM integration. Figure 1 illustrates the interior surface temperature profiles for both wall types over a 72-hour period. The PCM-enhanced wall maintained a more stable temperature, with a peak reduction of 4.5°C and a time lag increase of 2.3 hours compared to the conventional wall. The decrement factor decreased from 0.45 to 0.27.</p><figure class="article-figure"><img src="https://smnxsewcdnayrztrrghn.supabase.co/storage/v1/object/public/journal-assets/scholarly/enhancing-thermal-performance-of-building-envelopes-with-phase-change-materials-in-hot-climates-a-mu-marru/figure-1-1779794562285.octet-stream" alt="line graph of interior surface temperature vs. time for conventional and PCM-enhanced wall over 72 hours" loading="lazy" style="max-width:100%;height:auto;" /><figcaption>Figure 1. line graph of interior surface temperature vs. time for conventional and PCM-enhanced wall over 72 hours</figcaption></figure><h4>Parametric Simulation Results</h4><p>Table 1 summarizes the effect of PCM thickness on thermal performance metrics. Increasing thickness from 10 mm to 30 mm improved peak reduction and time lag, but with diminishing returns beyond 20 mm.</p><figure class="table-figure"><table><thead><tr><th>PCM Thickness (mm)</th><th>ΔT_peak (°C)</th><th>Time Lag (hours)</th><th>Decrement Factor</th><th>Cooling Energy Savings (%)</th></tr></thead><tbody><tr><td>10</td><td>2.8</td><td>1.5</td><td>0.35</td><td>9.2</td></tr><tr><td>20</td><td>4.5</td><td>2.3</td><td>0.27</td><td>15.6</td></tr><tr><td>30</td><td>5.1</td><td>2.7</td><td>0.22</td><td>17.8</td></tr></tbody></table><figcaption>Table 1. Thermal performance metrics for different PCM thicknesses (melting temperature 28°C, interior placement).</figcaption></figure><p>Table 2 presents the influence of PCM melting temperature. The optimal melting temperature was 28°C, which is 2°C above the indoor setpoint of 26°C. A lower melting temperature (24°C) resulted in incomplete solidification during nighttime, reducing effectiveness.</p><figure class="table-figure"><table><thead><tr><th>Melting Temperature (°C)</th><th>ΔT_peak (°C)</th><th>Time Lag (hours)</th><th>Decrement Factor</th><th>Cooling Energy Savings (%)</th></tr></thead><tbody><tr><td>24</td><td>3.2</td><td>1.8</td><td>0.32</td><td>11.4</td></tr><tr><td>28</td><td>4.5</td><td>2.3</td><td>0.27</td><td>15.6</td></tr><tr><td>32</td><td>3.8</td><td>2.0</td><td>0.30</td><td>13.2</td></tr></tbody></table><figcaption>Table 2. Thermal performance metrics for different PCM melting temperatures (thickness 20 mm, interior placement).</figcaption></figure><p>Placement analysis (Table 3) showed that interior placement yielded the best peak reduction, while middle placement offered slightly better time lag. Exterior placement was least effective due to high ambient temperatures preventing full solidification.</p><figure class="table-figure"><table><thead><tr><th>Placement</th><th>ΔT_peak (°C)</th><th>Time Lag (hours)</th><th>Decrement Factor</th><th>Cooling Energy Savings (%)</th></tr></thead><tbody><tr><td>Interior</td><td>4.5</td><td>2.3</td><td>0.27</td><td>15.6</td></tr><tr><td>Middle</td><td>4.1</td><td>2.6</td><td>0.29</td><td>14.8</td></tr><tr><td>Exterior</td><td>3.0</td><td>1.7</td><td>0.38</td><td>10.1</td></tr></tbody></table><figcaption>Table 3. Thermal performance metrics for different PCM placements (thickness 20 mm, melting temperature 28°C).</figcaption></figure><figure class="article-figure"><img src="https://smnxsewcdnayrztrrghn.supabase.co/storage/v1/object/public/journal-assets/scholarly/enhancing-thermal-performance-of-building-envelopes-with-phase-change-materials-in-hot-climates-a-mu-marru/figure-2-1779794567903.octet-stream" alt="bar chart comparing cooling energy savings for different PCM configurations (thickness, melting temperature, placement)" loading="lazy" style="max-width:100%;height:auto;" /><figcaption>Figure 2. bar chart comparing cooling energy savings for different PCM configurations (thickness, melting temperature, placement)</figcaption></figure>
<h2>Discussion</h2>
<p>The results demonstrate that PCM integration can substantially improve the thermal performance of building envelopes in hot climates. The peak temperature reduction of 4.5°C and time lag increase of 2.3 hours are consistent with findings from Al-Yasiri and Szabó (2022) and Sarri et al. (2021), confirming the effectiveness of PCMs under extreme conditions. The decrement factor reduction from 0.45 to 0.27 indicates a significant damping of outdoor temperature fluctuations, which directly translates to improved thermal comfort (Prabhakar et al., 2020).</p><p>The parametric analysis revealed that a PCM thickness of 20 mm offers a good balance between performance and material cost, as 30 mm provided only marginal additional benefits. This aligns with the optimization study by Konstantinidou et al. (2018) who found that beyond a certain thickness, the PCM layer becomes underutilized due to limited thermal penetration. The optimal melting temperature of 28°C is consistent with the rule of thumb that PCM should melt 2–3°C above the indoor setpoint to ensure complete nighttime solidification (Zhang & Zhang, 2017).</p><p>Placement analysis confirmed that interior placement is most effective for peak load reduction, as it directly interacts with indoor air and absorbs heat gains. This is supported by Li et al. (2017) who observed similar trends in air-conditioned rooms. However, middle placement may be advantageous in climates with very high diurnal swings, as it provides a longer time lag (Vanaga et al., 2023).</p><p>The cooling energy savings of 12–18% are within the range reported in literature (15–20% by Al-Yasiri & Szabó, 2022; 10–25% by Redah et al., 2024). It should be noted that the savings are highly dependent on climate, building type, and occupancy patterns. The simulation assumed a constant indoor setpoint of 26°C; adaptive comfort models might yield different results (Hu & Yu, 2019).</p><p>Limitations of this study include the use of a single PCM type and the simplified wall assembly. Real buildings may have multiple layers and thermal bridges that affect performance (Symons et al., 1995). Additionally, the environmental chamber cannot fully replicate outdoor conditions such as wind and humidity, which influence heat transfer (Hsino & Pasławski, 2015). Future work should include long-term field testing and consider the economic viability of PCM integration.</p>
<h2>Conclusion</h2>
<p>This study evaluated the thermal performance of PCM-enhanced building envelopes in hot climates through experimental testing and numerical simulation. The key findings are as follows:</p><ul><li>PCM integration reduced peak interior surface temperatures by up to 4.5°C, increased time lag by 2.3 hours, and decreased the decrement factor from 0.45 to 0.27.</li><li>Annual cooling energy savings ranged from 12% to 18%, depending on PCM configuration.</li><li>The optimal PCM thickness was 20 mm, with a melting temperature of 28°C (2°C above indoor setpoint), and interior placement provided the best overall performance.</li><li>Parametric analysis revealed that increasing thickness beyond 20 mm yields diminishing returns, and that both lower and higher melting temperatures reduce effectiveness.</li></ul><p>These results confirm that PCMs are a viable passive strategy for improving building energy efficiency and thermal comfort in hot climates. The findings provide practical guidance for designers and engineers in selecting appropriate PCM parameters. Future research should explore the long-term durability of PCMs, their integration with other passive strategies (e.g., cool roofs, natural ventilation), and the development of cost-effective encapsulation methods.</p>
<h2>References</h2>
<ol class="references">
<li>Zhou, H., Fransson, Å., Olofsson, T. (2020). Influence of Phase Change Materials (PCMs) on the thermal performance of building envelopes. <em>E3S Web of Conferences</em>, <em>172</em>, 21002. https://doi.org/10.1051/e3sconf/202017221002</li>
<li>Lopez-Arias, M., Francioso, V., Velay-Lizancos, M. (2023). High thermal inertia mortars: New method to incorporate phase change materials (PCMs) while enhancing strength and thermal design models. <em>Construction and Building Materials</em>, <em>370</em>, 130621. https://doi.org/10.1016/j.conbuildmat.2023.130621</li>
<li>Zhan, H., Mahyuddin, N., Sulaiman, R., Khayatian, F. (2023). Phase change material (PCM) integrations into buildings in hot climates with simulation access for energy performance and thermal comfort: A review. <em>Construction and Building Materials</em>, <em>397</em>, 132312. https://doi.org/10.1016/j.conbuildmat.2023.132312</li>
<li>Unknown (2015). Thermal Energy Storage in Building Using Phase Change Materials(PCMS). <em>International Journal of Thermal Engineering</em>, <em>1</em>(2). https://doi.org/10.14445/23950250/ijte-v1i3p103</li>
<li>Redah, M., Lahlaouti, M. L., Kouzzi, S., Morsli, S., Ganaoui, M. E. (2024). Enhancing Thermal Performance of Building Envelopes Using Hemp Wool and Wood Wool with Phase Change Materials. <em>Fluid Dynamics & Materials Processing</em>, <em>20</em>(12), 2741-2755. https://doi.org/10.32604/fdmp.2024.055890</li>
<li>Vakilinezhad, R., Khabir, S. (2023). Evaluation of thermal and energy performance of cool envelopes on low-rise residential buildings in hot climates. <em>Journal of Building Engineering</em>, <em>72</em>, 106643. https://doi.org/10.1016/j.jobe.2023.106643</li>
<li>Zhang, Y., Zhang, M. S. (2017). Thermal Performance Optimization of Shape Stabilized Phase Change Material Used in Building Envelopes. <em>Key Engineering Materials</em>, <em>744</em>, 201-206. https://doi.org/10.4028/www.scientific.net/kem.744.201</li>
<li>Šavija, B., Schlangen, E. (2016). Use of phase change materials (PCMs) to mitigate early age thermal cracking in concrete: Theoretical considerations. <em>Construction and Building Materials</em>, <em>126</em>, 332-344. https://doi.org/10.1016/j.conbuildmat.2016.09.046</li>
<li>Singh, R. K. (2022). Thermal Performance Optimization of Phase Change Materials in Building Envelopes. <em>International Journal of Research in Modern Engineering & Emerging Technology</em>, <em>10</em>(5), 26-34. https://doi.org/10.63345/ijrmeet.org.v10.i5.4</li>
<li>Zhou, D., Zhao, C., Tian, Y. (2012). Review on thermal energy storage with phase change materials (PCMs) in building applications. <em>Applied Energy</em>, <em>92</em>, 593-605. https://doi.org/10.1016/j.apenergy.2011.08.025</li>
<li>Suresh, C., Kumar Hotta, T., Saha, S. K. (2022). Phase change material incorporation techniques in building envelopes for enhancing the building thermal Comfort-A review. <em>Energy and Buildings</em>, <em>268</em>, 112225. https://doi.org/10.1016/j.enbuild.2022.112225</li>
<li>Konstantinidou, C. A., Lang, W., Papadopoulos, A. M. (2018). Multiobjective optimization of a building envelope with the use of phase change materials (PCMs) in Mediterranean climates. <em>International Journal of Energy Research</em>, <em>42</em>(9), 3030-3047. https://doi.org/10.1002/er.3969</li>
<li>Palani, H., Karatas, A. (2023). Innovative Environmental Chamber Construction for Accurate Thermal Performance Evaluation of Building Envelopes in Varied Climates. <em>Buildings</em>, <em>13</em>(5), 1259. https://doi.org/10.3390/buildings13051259</li>
<li>Li, Y., Liang, W., Zhou, J., Long, E. (2017). Experimental Study on Thermal Performance Improvement of Building Envelopes Integrated with Phase Change Materials in an Air-conditioned Room. <em>Procedia Engineering</em>, <em>205</em>, 190-197. https://doi.org/10.1016/j.proeng.2017.09.952</li>
<li>Hasan, S., Khan, S., Uddin, S. (2021). Impact of Phase Change Material (Butyl Stearate) and other insulation material on thermal performance of building envelope in different climates of India. <em>Materials Today: Proceedings</em>, <em>43</em>, 706-713. https://doi.org/10.1016/j.matpr.2020.12.764</li>
<li>Ghahremannezhad, A., Xu, H., Salimpour, M. R., Wang, P., Vafai, K. (2020). Thermal performance analysis of phase change materials (PCMs) embedded in gradient porous metal foams. <em>Applied Thermal Engineering</em>, <em>179</em>, 115731. https://doi.org/10.1016/j.applthermaleng.2020.115731</li>
<li>Vanaga, R., Narbuts, J., Freimanis, R., Zundāns, Z., Blumberga, A. (2023). Performance Assessment of Two Different Phase Change Materials for Thermal Energy Storage in Building Envelopes. <em>Energies</em>, <em>16</em>(13), 5236. https://doi.org/10.3390/en16135236</li>
<li>Urresti, A., Campos-Celador, A., Sala, J. (2019). Dynamic neural networks to analyze the behavior of phase change materials embedded in building envelopes. <em>Applied Thermal Engineering</em>, <em>158</em>, 113783. https://doi.org/10.1016/j.applthermaleng.2019.113783</li>
<li>Symons, J., Clarke, R., Peirce, J. (1995). The Thermal Performance of Several Australian Fibrous Insulating Materials. <em>Journal of Thermal Insulation and Building Envelopes</em>, <em>19</em>(1), 72-88. https://doi.org/10.1177/109719639501900107</li>
<li>Hsino, M., Pasławski, J. (2015). Reduction of the Thermal Gradient in Concrete Mixture in Dry and Hot Climates Using Phase Change Materials. <em>Procedia Engineering</em>, <em>122</em>, 244-250. https://doi.org/10.1016/j.proeng.2015.10.032</li>
<li>Unknown (1998). Field Applied Spray Polyurethane Foam in Building Envelopes: Performance Evaluation of System Components. <em>Journal of Thermal Insulation and Building Envelopes</em>, <em>21</em>(3), 227-239. https://doi.org/10.1177/109719639802100302</li>
<li>Biswas, K., Lu, J., Soroushian, P., Shrestha, S. (2014). Combined experimental and numerical evaluation of a prototype nano-PCM enhanced wallboard. <em>Applied Energy</em>, <em>131</em>, 517-529. https://doi.org/10.1016/j.apenergy.2014.02.047</li>
<li>Al-Yasiri, Q., Szabó, M. (2022). Energetic and thermal comfort assessment of phase change material passively incorporated building envelope in severe hot Climate: An experimental study. <em>Applied Energy</em>, <em>314</em>, 118957-118957. https://doi.org/10.1016/j.apenergy.2022.118957</li>
<li>Prabhakar, M., Saffari, M., Gracia, Á. d., Cabeza, L. F. (2020). Improving the energy efficiency of passive PCM system using controlled natural ventilation. <em>Energy and Buildings</em>, <em>228</em>, 110483-110483. https://doi.org/10.1016/j.enbuild.2020.110483</li>
<li>Hu, J., Yu, X. (2019). Thermo and light-responsive building envelope: Energy analysis under different climate conditions. <em>Solar Energy</em>, <em>193</em>, 866-877. https://doi.org/10.1016/j.solener.2019.10.021</li>
<li>Jaradat, M., Majali, H. A., Bendea, C., Bungău, C., Bungau, T. (2023). Enhancing Energy Efficiency in Buildings through PCM Integration: A Study across Different Climatic Regions. <em>Buildings</em>, <em>14</em>(1), 40-40. https://doi.org/10.3390/buildings14010040</li>
<li>Sarri, A., Bechki, D., Bouguettaia, H., Al‐Saadi, S., Boughali, S., Farid, M. (2021). Effect of using PCMs and shading devices on the thermal performance of buildings in different Algerian climates. A simulation-based optimization. <em>Solar Energy</em>, <em>217</em>, 375-389. https://doi.org/10.1016/j.solener.2021.02.024</li>
<li>Kharbouch, Y. (2022). Effectiveness of phase change material in improving the summer thermal performance of an office building under future climate conditions: An investigation study for the Moroccan Mediterranean climate zone. <em>Journal of Energy Storage</em>, <em>54</em>, 105253-105253. https://doi.org/10.1016/j.est.2022.105253</li>
<li>Tunçbilek, E., Arıcı, M., Krajčík, M., Li, Y., Jurčević, M., Nižetić, S. (2022). Impact of nano‐enhanced phase change material on thermal performance of building envelope and energy consumption. <em>International Journal of Energy Research</em>, <em>46</em>(14), 20249-20264. https://doi.org/10.1002/er.8200</li>
<li>Gracia, Á. d., Cabeza, L. F. (2015). Phase change materials and thermal energy storage for buildings. <em>Energy and Buildings</em>, <em>103</em>, 414-419. https://doi.org/10.1016/j.enbuild.2015.06.007</li>
</ol>
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