Microencapsulated phase change materials (MPCM) incorporated in buildings walls can reduce indoor temperature fluctuations, conserving energy and enhancing thermal comfort. MPCM were incorporated in calcium sulphoaluminate cement (CSA) at high concentrations to achieve a significant effect on the thermal properties. The cement hydration development was studied by isothermal calorimetry and laboratory X-ray powder diffraction (LXRPD). The hydration mechanism was not affected by the addition of MPCM. In order to obtain homogeneous mortars in the presence of MPCM, a superplasticizer (SP) was used. However, the SP causes a significant delay of the hydration. Although the mineralogical composition of the hydrated pastes did not change with the addition of MPCM, the mechanical strengths decrease dramatically. This decrease is well described by the Bolomey equation, assuming MPCMs act as air voids. This is a physical effect due to the high volume of MPCM, and not due to a change in the hydration chemistry.