This paper is about the necessity to use Cash Flow Discounting (CFD) models integrated in Environment Systems for the appraisal of property over a specific period of time. The first part of the study develops, in a short, but rigorous manner, the concepts which recommend dropping the restrictions of estaticity of the dynamic variables which affect the future income flow of the assets to be valued, the quantification of errors which result, and the new methodology on which the new focus on CFD integrated in Environment Systems (ES) is based. The last part of the paper looks at a practical application using the CFD+ES model, developed by EUROVALÆ, to calculated the value and return adjusted for risk of housing developments that are for sale.