- The current research explores both experimentally and theoretically the thermal performance of transported insulated cold storage packages that can keep products at a low temperature. In order to sustain the product cold as long as possible, it is suggested to combine a conventional insulation with a phase-change material (PCM), thus taking advantage of its latent heat. A number of useful modelling approaches are suggested and tested for an insulation-PCM system. First, a rather simplified, but still preserving the main physical traits of the problem, analytical model is developed. This model reveals the dimensionless groups that govern the problem. It also shows the existence of an optimal insulation thickness that maximizes the melting time of the PCM, and thus keeps the product at a low temperature for a longer period. Then, a more exact, yet fast and computationally inexpensive, numerical model is introduced. This conduction-based model, which takes into account the three-dimensional structure of the insulation and natural convection, is validated against experiments performed on two packages, with different dimensions and PCMs. Both experimental and numerical results show that the heating process can be divided into five different physical stages. The good agreement between the experiments and the numerical model makes it possible to use the latter in design of similar systems.