This study investigates the impact of varying waste dosages and temperature fluctuations on the thermal properties of lightweight concrete. Specifically, the research utilizes shredded plastic, polystyrene, and sawdust as partial substitutes for traditional aggregates, employing a central composite design methodology. This experimental approach involved the creation and testing of 14 different concrete mixes. One mix served as the control with no aggregate replacement, while the remaining 13 incorporated varying proportions of waste materials as partial aggregate substitutes. The analysis utilized nonlinear response surface methodologies to effectively evaluate the influence of each variable on thermal performance. The study found that the mix incorporating polystyrene granules as an aggregate substitute exhibited the lowest thermal conductivity coefficient, indicating superior insulative properties. Furthermore, specific thermal isolation performances were observed at high dosages: a 50% polystyrene mix achieved the maximum temperature difference (ΔT) under external temperatures of 55 ℃; a 70% shredded plastic mix showed maximum ΔT at 50 ℃; and a 50% sawdust mix was most effective at 40 ℃. Comparatively, 100% polystyrene mixes consistently outperformed other materials in terms of ΔT and had significantly lower thermal conductivity (λ), underscoring their effectiveness in high-temperature scenarios. The incorporation of waste materials as aggregates in all the mixes showed great potential for isothermal insulation, showing their suitability for construction purposes aimed at improving thermal efficiency.