The prediction of energy use, air flows and temperatures in different rooms of a building andat different climatic conditions is very important, especially when evaluating new conceptsfor heating and ventilation systems in combination with different building envelopeconstructions. A thorough system analysis considering coupled air flow and thermalcalculations becomes very complex if e.g. thermal bridges and dynamic conditions areconsidered. The substance of this paper is to describe a relatively simple methodology forsystem analysis that has been applied to a house and to compare obtained results frommeasurements and calculations.The methodology consists of initial calculation of air flows using the multi-zone model IDAMAEfor different configurations and climatic conditions. The air flows are then included in aTSBI3 computer model for temperature and energy use calculations.User-friendly computer tools that combine multi-zone air flow and thermal calculations aredesired to simplify a sensitivity analysis, and this will also increase the precision in thepredictions. This development is in progress internationally. Further development of fieldmethods to measure the air leakage characteristics of building components and individual airleakage paths would be useful to increase the knowledge of especially interior air leakagepaths in buildings.The evaluated building concept, called TEEG, uses a heated crawlspace to distributeventilation and heating air through gaps in the floors along the external walls. As the systemrelies on distribution of warm air through gaps in the floors, it becomes very sensitive touncontrolled air leakage paths. Measurements of air leakage become an important qualitycontrol tool for buildings using this concept.