Heating experiments have been performed during 1.5-18 days in a confined room of volume about 300 m 3 in an underground quarry near Paris (France). During heating, a thermal stratification of the atmosphere is observed. After a time depending on the presence or not of ventilation, this stratification reaches a stationary state during which the temperature difference between the rock and the atmosphere is constant. During this stationary phase, both temperatures increase linearly with time. We propose here a new model of filling box with radiative heat exchanges and cooling by direct contact at the boundaries, which accounts for the observed vertical profiles of temperature in the atmosphere, and for the temperature variation with time. Such contributions of heat transfer at the boundaries are important in situations such as fire in confined cavities, presence of visitors in a painted cave, or in the study of building ventilation. (c) 2006 Elsevier Ltd. All rights reserved.