Impact of the natural ventilation on the building depends on the design of the several components of the building like facade, HVAC and control system. Paper presents several tests of the building with different selection of the components. The double skin facade is compared to the single skin facade with the external or internal shading device and with climate wall. Furthermore, impact of the mechanical or natural night cooling, predictive control is discussed. Final solution represents the possible reduction in HVAC system to balance the costs of the double skin facade. The tests were carried out with the simulation program built in Simulink(TM) validated with the measurements taken in Test cell at TU Delft as well as in the real office building. Each solution is qualified based on differences in capacities, energy consumptions and costs for various solutions of facade, HVAC system and control. As a final solution optimization of the HVAC system is presented (C) 2004 Elsevier B.V. All rights reserved.