Effort estimation is a long faced problem, but, in spite of the amount of research spent in this field, it still remains an open issue in the software engineering community. This is true especially in the case of renewal of legacy systems, where the current and well established approaches also fail. This paper presents an application of the method named Dynamic Calibration for effort estimation of renewal projects together with its experimental validation. The approach satisfies all the requirements of the estimation models. The results obtained applying dynamic calibration are compared with those obtained with a competitor method: estimation by analogy. The results are shown to be promising although further experimentation on field is needed.