Heating from geothermal doublets might contribute to the adaptation from fossil energy into greener methods for a CO2-neutral future. Recently, P. van Nieuwkerk (2022) has demonstrated how a new upscaling method developed by Tang et al. (2022) produces more accurate predictions of production temperature over time when an increase in the vertical thermal conductivity parameter (kz) is implemented in simulations. The results of Van Nieuwkerk's research might be used in optimising geothermal doublet performance. This thesis explores whether a justified physical reason for increasing kz exists. Concretely, this study compares analytical solutions and modelled solutions, based on a simplified layer-cake model, of a situation of conductive heat transfer for which analytical solutions already exist. A technique called superposition has been applied to both solutions in order to match the in situ situation more accurately. Results of the most realistic cases that have been investigated show that the modelled and analytical solutions do not vary considerably in temperature predictions over time. Therefore, this research has not identified any physical grounds that justify an increase in kz. Nevertheless, since this report has only considered a simplified model that bears limited resemblance to the in situ situation, it does not mean that there is none. Based on these results, future research is necessary to make more specific evidentiary claims.