Laser additive manufacturing, and specifically laser powder bed fusion (PBF-LB) enables the production of complex geometries with optimized features that provide unique features to components. One of the main advantages of PBF-LB is its capability to produce reticular or lattice-type geometries that considerably reduce the weight of the components. Lattice geometries are widely used to optimize components mechanically, but, to date, their thermal capabilities have not been studied in depth. Therefore, in the present work, the thermal behavior of lattice structures is analyzed experimentally and correlated with finite element models. Nevertheless, the simulation of lattice structures is highly costly from a computational point of view. In order to solve this issue, the present work develops a novel methodology based on fictitious solid materials that behave thermally as the lattice structure. The results show strong resemblance between the thermal behavior of fictitious solid and lattice structures, with temperature errors below 2%, and it reduces the computational cost required for their simulation by up to 90%. Moreover, the obtained results open the door to the design of anisotropic components based on lattice structures, as well as increasing the design capabilities for this type of structure.