Advancing energy savings and CO₂ emission reductions in lightweight concrete with bio-based polyurethane phase change material for sustainable building applications

Improving the energy efficiency of building materials is critical for reducing environmental impacts. This study develops and evaluates bio-based polyurethane composites (BPUCs) incorporating lauryl alcohol (LA) as a phase change material (PCM) for lightweight cementitious systems. The composites were synthesized from modified castor oil (MCO), commercial polyether polyol (CPP), and methylene diphenyl diisocyanate (MDI), and systematically characterized to assess their thermal, mechanical, microstructural, and environmental performance. Differential scanning calorimetry, thermogravimetric analysis, hardness, tensile, and thermal conductivity tests were performed, followed by outdoor thermal regulation testing using a full-scale cabin setup. Results show that increasing LA content improves bulk density (38.9–67.6 kg/m³), hardness (7.1–15.2), and thermal conductivity (0.026–0.038 W/m·K), while moderately reducing tensile strength (243–138 kPa) and strain (89–43 %). The optimized composite, BPUC-LA-6, achieved a latent heat storage of 127.8 J/g and enhanced thermal stability, with activation energy increasing from 108.47 to 164.13 kJ/mol. When incorporated into lightweight cementitious composites (BLWC3), the system reduced peak surface temperatures by up to 6.5 °C and maintained nighttime warmth by approximately 2 °C, confirming its effective thermal energy storage behavior. Energy simulations across different Turkish climate zones indicated heating energy reductions up to 60 % in severe climates, accompanied by proportional decreases in CO₂ emissions. The economic analysis showed annual savings between $0.65 and $4.39 per square meter depending on the heating source, with a payback period of 2–15 years. This work presents a scalable bio-based polyurethane–PCM system that integrates renewable materials with high PCM loading, offering a practical route to energy-efficient and low-carbon building materials.