Our paper presents research on the development of technologies and methodologies to support preliminary design phases through data based modelling. A digital parametric model informs costs evaluations and supports iterative and visual space exploration solutions. Thanks to associative modelling, the architectural conception is renewed and digital tools support design decision-making in a creative way. We propose to make project cost a design parameter through an interactive handling of a 3D geometric model that is relevant to strategic architectural intentions. In our experimentation, cost calculation spreadsheets are linked to a parametric models. An initial substructure of the building cost is defined based on the architectural concepts. The parametric tool directly informs the evaluation spreadsheet and a real time cost analysis is afforded to the designer. The tool supports the design process by displaying immediate feed back to the designer who can consider and control the financial implications of his hypothesis.