Development and performance of phase change materials integrated envelopes for sustainable and energy-efficient building design

Abstract

Enhancing building energy efficiency is a key strategy for achieving sustainable development and combating climate change. One innovative approach involves the use of Phase Change Materials, which demonstrate significant potential in thermal performance. These materials absorb and release substantial amounts of latent heat during phase transitions, helping to stabilize indoor temperatures fluctuation. By integrating PCMs into building envelope and design, construction practices can be transformed, leading to reduced energy consumption, lower carbon emissions, and more sustainable solutions. PCMs can store significant latent heat during phase transitions, making them ideal for passive design strategies aimed at reducing space cooling demands in hot climates. Roofs, as key building envelopes exposed to sunlight, transfer significant heat indoors, increasing space cooling needs. PCMs can enhance thermal mass and reduce heat transfer, yet research on integrating large macroencapsulation of PCM into roofs for effective thermal management in hot climates is largely lacking. A need to develop roof designs with enhanced PCM integration and thermal mass to improve indoor thermal management under hot climatic conditions motivates the present work. This dissertation presents a comprehensive experimental investigation into the integration of macroencapsulated and microencapsulated phase change materials to enhance the thermal and energy performance of building envelope systems, with a particular focus on roof structures and fly ash bricks. PCM modules spherical, cylindrical truncated spherical, and hollow clay tile compatible were developed for seamless integration into hollow concrete roofs. A range of rooftop configurations, including single-layer, dual-layer, and multi-PCM assemblies, were designed to optimize thermal resilience across diverse climatic conditions. Advanced characterization methods evaluated the thermal, physical, chemical and morphological properties of various PCMs, including MePCMs synthesized from waste shell materials. Multiple design approaches such as zone-based, dual-layered, and strip-based approaches were evaluated to optimize PCM performance. Thermal performance metrics including indoor temperature reduction (up to 25.4 °C), heat flux suppression (up to 79.8%), thermal buffering capacity, key performance index, thermal efficiency and thermal damping demonstrated the effectiveness of PCM enhanced roof systems, with significant improvements in thermal load levelling and energy savings. Furthermore, thermal storage performance measures such as heat gain, time lag, and decrement factor are evaluated. Notably, Dual-layer PCM-integrated roof system proved highly effective for hot climates, while a novel zone-based design facilitated the simultaneous evaluation of multiple variables. The thermal performance of multi-PCM-integrated roof strips varied with ambient conditions throughout the testing period. Particularly, strip OM30 demonstrated pronounced phase change activity during March, indicating strong responsiveness to transitional seasonal temperatures. By June, all PCM strips had become fully active, with pairs such as OM35 and OM37 exhibiting comparable thermal behavior, which significantly contributed to the improvement of the roof's thermal performance. Among the tested materials, strip OM30 yielded the greatest reduction in interior surface temperature, while OM35 consistently showed superior thermal efficiency across all seasons. During winter, OM35 achieved thermal efficiency values ranging from 64.39% to 66.47%, outperforming other strips, which ranged between 50.15% and 55.35%. This high performance was sustained through spring and summer, with OM35 reaching a peak efficiency of 67.22%. Microencapsulation using expanded polystyrene and nano silica successfully encapsulated the PCM and established a suitable synthesis template. The MePCM integrated fly ash brick demonstrated daily maximum temperature reduction of up to 18.23 °C, with a minimum of 8.18 °C and an average of 13.76 °C. Furthermore, it exhibited enhanced thermal inertia, resulting in a peak temperature reduction of up to 7.04 °C and a decrease in peak heat flux by 30.6%. The study further revealed the economic viability of PCM integrated systems through reduced energy costs, shortened payback periods, and decreased carbon emissions. Key innovations include integration multi PCMs into hollow concrete roof with complete PCM leakage prevention using PCM modules, embedding of MaPCMs within concrete matrices, and the introduction of new encapsulation typologies. New MePCMs synthesised, characterized and thermal performance evaluated integrated in to fly ash brick. The findings offer a robust foundation for climate-adaptive, energy-efficient building design and highlight the significant role of PCMs in passive thermal regulation. From the study, it can be concluded that the proposed PCMs integrated roofs and MePCM integrated fly ash brick is promising and commercially viable.