This paper presents a system to incorporate the economic benefits of sustainability into the valuation of real estate project developments. The impact is provided through the consideration of quantified sustainable qualities of buildings in the determination of the interest rate in the valuation process. Furthermore, it highlights the added value that sustainable features and the relevant certification systems bring to a project development. Using a catalogue of parameters, key parameters are identified for the specific project development to be valuated. These parameters are then quantified by means of distribution functions and checked for interdependencies. This analysis, and with it the results of a sustainability valuation, are incorporated into the calculation of the market value and the internal rate of return. Results are communicated according to the input data through distribution functions. The valuation system makes investment decisions easier to understand and emphasises the positive impact that sustainable features can have on the economic success of real estate projects. (C) 2014 Elsevier B.V. All rights reserved.