Energy efficiency - a key to sustainable housing

Energy efficiency in buildings is amongst the economically most interesting options for the reduction of greenhouse gas emissions. So-called Passive Houses have proven to be able to reduce the heating demand of buildings in central European climates by approximately 90% as compared to the existing building stock, at reasonable cost. This is mainly achieved by reducing, to a large extent, all heat losses from the building. The present contribution focuses on some physical aspects of the Passive House principle. It shows how physical reasoning contributed to accurate tools for the prediction of energy consumption and to actual energy savings.