Polyurethane (PU) foam is a material that has long been regarded as a good thermal insulator for building purposes due to many advantageous attributes, such as cost and feasibility. Yet, to further develop its performance, many studies have focused on the potential of using the micro-structure of PU foam as an encapsulation for PCMs. Despite the apparent advantageous outcome of this premise, from the perspective of thermal performance, fire-retardation issues may pose as a threat. PU foam is known for its inherent poor fire-retardation properties. With the addition of PCMs, especially wax-based, it is possible that the fire-retardation would worsen. This would translate into additional costs in terms of application of treatments to counter the disadvantageous hazardous properties. In this study, an empirical investigation is carried out with the aim of determining whether addition PCMs to PU foam would influence its retardation, and to which extent. In this context, granules of wax-based PCMs are encapsulated in to closed-cell rigid PU foam via a simplified amalgamation method. Two concentrations of PCM content are presented in this paper. Then, fire-retardation testing is performed on specimens to compare the performance of the created PU/PCM specimens with this of regular PU specimens. The outcome of this empirical investigation further confirms that addition of PCM to PU foam is disadvantageous in terms of fire-retardation, and that the amount of added PCM is of considerable influence on this.