Energy consumption in buildings represents 40% of the final energy demand in Europe – and they consume more energy than any other sector of the European economy [1]. About half of the energy consumed in building operation is invested into heating, ventilation and air conditioning (HVAC) [2], whereby in the US ventilation represents about 61% of the total electric power consumption in office HVAC systems [3]. In many modern buildings the air conditioning system does not contribute significantly to heating or cooling, but shall rather condition the indoor air to be at the right level of CO2 and within the comfort zone in the Mollierh-x diagram. In this work, the authors therefore focus on energy optimizations based on volume flow reductions and disregard the energy needed for heating or cooling the air as well as the energy for adjusting the humidity – based on the valid assumption that ∗ Corresponding author. E-mail address: gerhard.zucker@ait.ac.at (G. Zucker). reduced volume flow will in parallel also save energy for heating, cooling, humidification and dehumidification. At the same time, buildings need to balance between maximum energy efficiency and optimal indoor air composition and quality (IACQ). IACQ has gained great importance due to the significant increment of illnesses reported by building occupants, referred as sick building syndrome (SBS) [4,5]. Z. Lin et al. [6] suggest that multiple factors are involved in this syndrome, including indoor air quality (IAQ) such as microbiological and chemical exposures not adequately characterized by current assessment approaches. This study also shows that with proper design, installation, maintenance and operation, the ventilation mechanisms of buildings can maintain satisfactory levels of IAQ and therefore reduce the SBB incidence. Today there is no real integration of IACQ and energy efficiency, being mainly the domains of different communities working independently. Different studies [7,8] have shown that some energy efficient buildings reduce the conventional energy consumption by means of reducing volume flow with a number of ventilations below the standards, and therefore a reduction on IACQ. By observing how HVAC designers commonly address the above 40% of energy use for space heating and cooling, it is found out that the design focuses on minimizing energy use/cost, which often leads to unhealthy indoor comfort conditions.