The present work numerically investigates the influence of partitions on buoyancy induced convection with thermal radiation in a differentially heated cubical enclosure. Four distinct arrangements of partitions from the top-bottom and front-back walls are examined by adopting a symmetric (inline) and asymmetric (offset) configuration of partitions. An in-house three-dimensional numerical solver based on low-Mach number formulation is employed for the numerical simulations of high-temperature natural convection as well as combined convection with surface and gas radiation. Comparative analysis of average and local Nusselt number variation at the isothermal walls and temperature variation inside the enclosure is presented for all configurations of partitions considered. Irreversibilities associated with conduction, convection, and radiation heat transfer with viscous dissipation are studied to investigate the role of partitioning walls in overall volumetric entropy production. This study also aims at determining the optimum design (higher heat transfer rates with minimum entropy production) among all partition configurations. The simulation results reveal that heat transfer irreversibility is the dominant mechanism of entropy production. Furthermore, offset configuration of front-back partitions could be a preferred choice in the practical design of buildings where the impact of combined convective-radiative heat transfer is significant. © 2018 Elsevier Ltd