Simulations of the flow of heat through porous thin films by the three-dimensional microstructural thin film simulation framework 3D-Films are discussed in this paper. For each simulation, the film structures are generated by the thin film growth model 3D-Films and then used to generate a finite difference based thermal model by the program 3D-Films/Thermal. This program creates a block based data structure using a 3D quadtree mesh and subsequently solves for the steady state heat Row through the film structure. In this paper the film growth and thermal models are used to analyze and suggest optimization of porous thermal barrier coatings produced by glancing angle deposition techniques. The paper also deals with the determination of the accuracy and efficiency of the thermal model. Studies on the effect of reducing the resolution of the simulated film for less memory intensive thermal simulations are presented, indicating that a reduction of the resolution by a factor of 3 and the number of solution variables by as much as a factor of 27 is feasible. The simulations Of ZrO2 thermal barriers are compared to experimental results with a relatively close match being obtained. Finally, the simulator is used to analyze the effectiveness of a number of potential thermal barrier structures produced by glancing angle deposition techniques. These results suggest that the most effective thermal barrier film microstructures will be porous films consisting of slanted posts or large pitch helices.