The aim of this paper is to investigate the effects of convection and radiation from a high-temperature heat source on the thermal environment in an industrial building. The relevant control parameters include the Grashof numbers, which range from 107 to 1011, and the surface emissivity with values of 0.2, 0.5 and 0.8. The ratio between radiation and convection from the heat source is proposed as an important parameter for predicting the effects of heat transfer. Detailed results are discussed regarding the temperature and flow distributions, the heat transfer on the heat source surface and the ventilation rate. The dimensionless temperature and velocity profiles above the heat source are presented for different Grashof numbers. In addition, the Nusselt numbers on the heat source surface and the ventilation rate are investigated. It is observed that the ratio between radiation and convection is a decreasing function of the Grashof number and an increasing function of the surface emissivity. The total Nusselt number and the ventilation rate are both increasing functions of the Grashof number and the surface emissivity. (C) 2014 Elsevier B.V. All rights reserved.