Mixed convection in a porous layer with a superposed fluid layer heated over a finite length of the lower boundary has been investigated over a large parameter space. The numerical solution uses a one-domain model and avoids the need to explicitly define interface conditions at the fluid-porous sublayer interface. Additional variable porosity terms have been derived to model interfacial effects in the momentum and energy equations. The measurement of overall Nusselt numbers on the heated surface has been conducted for a wide range of Rayleigh number, Péclet number, and porous sublayer height. The numerical results are found to generally fall within the bounds of experimental uncertainty. The following paragraphs summarize the key findings of this investigation.