In this work, the above room temperature heat capacity for different polymorphs of alkali and alkali-earth (i.e. Na, K, Rb, Cs, Mg, Ca) borohydrides has been measured by DSC as a function of temperature. The above room temperature measured C_p values have been compared with available extrapolated literature data, and they have been modelled as a function of temperature according to the Calphad method. The variations of C_p values for different polymorphs were studied in details and they have been related to the corresponding crystal structures, considering the mobility of the BH₄⁻ group. From the whole set of assessed thermodynamic data, possible correlations with dynamics and structural properties have been estimated.