Thermal insulation plays an important role in efficiency enhancement of heat transfer units by minimizing the loss of energy. However, the choice of insulation material determines the insulation value per unit thickness which in turn affects the total material thickness to gain the desired benefit. Therefore, the thermal properties of polyurethane (PU) rigid foam, which is the most effective insulation material, have been improved by introducing suitable Phase Change Materials (PCMs) to minimize the material thickness for a specific temperature application. Differential scanning calorimeter (DSC) has been intensively used to determine the thermal properties of the composites and reference foam. The thermal properties are given in terms of phase change temperature, enthalpy and total absorbed heat with related statistical data. The thermal stability of the PCM has also been investigated to clarify the leakage behavior throughout the matrix. The DSC analyses indicate that the total heat absorption capacity of reference foam is improved by ~ 21 % in the composite with respect to the total heat absorbed between 4°C and 87°C. The results show that (PU-PCM) composites are suitable for insulation of low temperature heat transfer units such as hot transfer lines and reactor or heat exchanger jackets with less material thickness than conventional PU rigid foams.