Integrating solar collectors as building elements is one of the most promising way to decrease the cost of the delivered energy and to increase the architectural acceptance of energy self-supplying buildings. For that purpose, steel-made coloured unglazed solar absorbers as facade elements were investigated. Besides the questions of building integration, selective layer, durability and industrial production, it is essential to study the potential yield of such devices and to optimize the design and sizing of the complete heating system. Simulations were carried out using the TNRSYS program in different European climates. Results show that the absorbers reach appreciable efficiency for domestic water preheating but rather low yields when connected to the space heating circuit. Sensitivity of the quantity of saved energy towards the sizing parameters (absorbance, emissivity, orientation, wind, surface, radiator outlet temperature) was analysed. Based on a large set of simulations, general formulas completed by a European map of constants required by said formulas were established that allow calculating the absorbers yield without running complete simulations. General conclusion is that the best use of facade absorbers is water preheating in urban (wind-sheltered) environment. (C) 2008 Elsevier Ltd. All rights reserved.