As successful products of the recent developments in the building industry aimed at increasing the energy efficiency of buildings, the hollow clay brick blocks with complex systems of internal cavities present a prospective alternative to the traditional solid bricks on the building ceramics market. Determination of their thermal properties, which are essential for any energy-related calculations, is though not an easy task. Contrary to the solid bricks, the application of sophisticated methods is a necessity. In this paper, a fast computational approach for the determination of equivalent thermal conductivity of hollow brick blocks with the cavities filled by air is presented, which can be used as an integral part of energy-related calculations. The thermal conductivity of the brick body is the main input parameter of the model, the convection and radiation in the cavities are taken into account in a simplified form. The error range of the designed method is identified using a thorough uncertainty analysis. A direct comparison of the calculated equivalent thermal conductivity with the results obtained by two different experimental techniques for the same hollow brick block shows a satisfactory agreement, making the designed computational approach a viable alternative to the currently used methods. (C) 2015 Elsevier Ltd. All rights reserved.