Shape stable phase change materials (SSPCMs) based on paraffin wax (PW) and high density polyethylene (HDPE) can be used as energy storage materials for utilization of renewable energy in buildings. An SSPCM could be formed by selecting a suitable wax in terms of melting temperature (T m) and a HDPE in terms of viscosity. However, the impact of waxes with different T m and HDPEs with different viscosities on the manufacture of SSPCMs and their thermo-physical properties has not been studied thoroughly. Therefore, the aim of the research reported in this thesis is to understand the effect of different waxes and HDPEs on the processing of SSPCMs typically used in buildings and the quantification of their thermal and mechanical propelties. SSPCMs based on a higher (H-PW, Tm = 56-58°C) and a lower (L-PW, Tm = 18-23 0c) Tm wax with a higher (hv-HDPE, MFI = 0.18) and a lower (lv-HDPE, MFI = 25) melt viscosity HDPE were prepared by an extrusion method and their thermal and mechanical properties investigated. The effect of addition of thermally conducting multi-walled carbon nanotubes (MWCNTs) to enhance thermal conductivity and other properties of these SSPCMs was also studied. Such understanding would thus help to assess and inform the design of SSPCMs as wall panels suitable for domestic applications.