Enhanced Roofs for Passive Building Design: A Systematic Review of Thermal and Energy Performance

ABSTRACT

Global building energy consumption continues to rise, with roof systems playing a critical role in uncontrolled heat gain and associated cooling loads, particularly in hot and humid climates. Although phase change materials (PCMs) and nano‐enhanced PCMs (NePCMs) have been widely explored for passive thermal regulation in roofs, the reported findings remain fragmented, with inconsistent performance due to variations in material properties, encapsulation techniques, roof configurations, and climatic conditions. This lack of a consolidated understanding limits their reliable implementation in energy‐efficient building design. To address this gap, this study presents a systematic review and critical synthesis of PCM‐ and NePCM‐integrated roof systems, integrating insights from experimental, numerical, and analytical investigations. The review specifically evaluates the influence of thermophysical properties, encapsulation strategies, geometric design of roof elements, and environmental conditions on thermal and energy performance. In addition, hybrid configurations combining PCMs with auxiliary cooling strategies such as night ventilation, reflective coatings, and radiative cooling layers are comparatively assessed to identify performance enhancement pathways. The findings indicate that while PCM‐integrated roofs consistently reduce peak indoor temperatures and dampen thermal fluctuations, their effectiveness is strongly governed by conductivity limitations and melting/solidification dynamics. Macroencapsulation remains the most widely adopted approach due to structural feasibility, though heat transfer limitations persist. NePCM systems demonstrate improved thermal response and faster energy exchange; however, trade‐offs in reduced latent heat storage capacity, long‐term stability, and cost are evident. Overall, hybrid and multilayered roof systems exhibit the greatest potential to enhance passive cooling.