Shovadan is the underground room which, for a long time, has been used in several areas of Iran for heating and cooling purposes. In the present work, Shovadan heating and cooling performance is experimentally investigated during a year. In the sample studied, when the ambient temperature is 7 degrees C in January and 47 degrees C in July, Shovadan average temperature is 17 degrees C and 23 degrees C, respectively. The suitable Shovadan temperature range proves the ability of this space in architecture optimization for saving energy. Next, in order to save time and cost to study more Shovadans in other locations, a three-dimensional model is simulated in real size. Then, Navier-Stokes and energy equations have been numerically solved and the temperature distribution within a Shovadan has been calculated. Numerical results are in good agreement with the experimental data. Finally, ventilation effectiveness was evaluated in the coldest and warmest months. (C) 2012 Elsevier Ltd. All rights reserved.