The article presents environmental analysis of a detached house in terms of its life cycle. The analysis is simplified in order to compare the built and operational energy of the building whereas the operational energy is described using computer aided building performance simulation. The input data related to the built (embodied) energy are based on information from classical works on life cycle analysis. The article also justifies the simplification of environmental analysis, which aims to build pragmatically on existing standardization and legislation on energy performance of buildings. The final section provides some considerations concerning the environmental assessment of buildings.