Natural ventilation of buildings has the potential to significantly save cooling and fan electrical energy. However, it is still not widely applied, because only limited information is available on the thermal comfort and indoor air quality of office buildings without air conditioning. Steady state ventilation air flow rates were therefore systematically simulated using both analytical and airflow network methods for different boundary conditions such as temperature and pressure differences across openings for different opening types. Coupled airflow network and dynamic building simulations were carried out to determine the annual thermal comfort and energy savings. The results for the three moderate climate locations Germany, Italy and Turkey show that while indoor air quality can be easily maintained for all opening typologies, the summer cooling potential and thermal comfort strongly depends on the natural ventilation strategy. Control over the openings is crucial for all cases, as otherwise the office rooms tend to cool down too much even in summer conditions. (c) 2012 Elsevier B.V. All rights reserved.