Investigating Thermal Performance of Building Materials for Improved Comfort and Energy Efficiency

This research investigates the mixed proportions of cement, sand, water, superplasticizer, and waste materials, like recycled concrete, recycled rubber, recycled wood, tea-leaf residue, and recycled plastic, with their replacement levels clearly reported for reliability. Eight mixes were manufactured and tested at the Kuwait Institute for Scientific Research (KISR). The samples were then cured for 28 days, and compressive strength and thermal conductivity were measured. The control mix (Mix 1) showed a thermal conductivity of 0.788 W/m·K, while the wood and plastic mix (Mix 7) showed the lowest value of 0.266 W/m·K, which is equivalent to good insulation performance. Thermal conductivity (k) and thermal resistance (R) were reported together to provide a complementary insulation assessment for 50 mm (R = 0.05/k). Relative to the control (k = 0.788 W/m·K, R = 0.063 m²·K/W), Mix 7 (wood + plastic) achieved the best insulation (k = 0.266 W/m·K, R = 0.188 m²·K/W), representing a 66.27% reduction in k and a 196.45% increase in R. Mix 2 also showed strong insulation gains (k = 0.316 W/m·K, R = 0.158 m²·K/W, −59.95% k, +149.67% R), whereas strength results indicate these highly insulating mixes are most suitable for non-load-bearing applications. Compressive strength varied significantly across mixes, ranging from 0.38 MPa in wood-plastic composites to 19.30 MPa in the control, highlighting the trade-off between strength and insulation. The outcomes of this research are the demonstration of the capacity of the recycled and organic additive options to create energy-efficient, eco-friendly building materials fit for Kuwait's hot climate.