The presentation describes development of a model to predict the macroscopic thermal resistance of mechanically contacting surfaces — a capability that is important for modeling thermal management in many industrial processes. Contacting interfaces are fractally rough, with small islands of locally intimate contact separated by regions with a wider gas filled boundary gap. Heat flow across the interface is therefore heterogeneous and thus the contact model is based on a network of thermal resistors representing boundary resistance at local contacts and the Sharvin resistance for transport laterally to contacts. In this work, we present the results of molecular dynamics simulations to characterize boundary resistance of silicon alumina interfaces, testing the sensitivity of thermal resistance to contact opening, and the influence of adsorbent layers. In addition, we report on Boltzmann transport simulations of Sharvin resistance in Si in the ballistic transport regime.