The objective of the research project LEKOECOS is to quantify the environmental and economic resources consumed by a building during planning, construction and in the utilisation and operation stage. The complexity of the utilisation process over the long life span requires a calculation model with well-orchestrated normative definitions and idealisations. The presented environmental-economical model is based on the life cycle costs model LEKOS, developed by the Danube University Krems, and the environmental assessment software ECOSOFT by IBO. A new consistent model architecture was built up in order to synchronise the different characters of the environmental and economic resources of the building along its life cycle. This new architecture enabled a holistic consideration of the consumption of the environmental resources from elements as well as from services over the whole life span.Purpose of the system integration is a combined economic and ecological life cycle model for buildings, realised in an easy-to-use tool for the evaluation of life span resource consumptions at different stages of the design process. In addition specific life cycle resource consumption parameters are defined. This allows to compare the environmental and economic impact of different building types of different sizes and of different planning variants.