This is the first volume of the conference proceedings of the 31st eCAADe conference, held from 18-20 September 2013 at the Faculty of Architecture of Delft University of Technology in Delft, the Netherlands. Both volumes together contain 150 papers that were submitted and accepted to this conference.The theme of the 31st eCAADe conference is the role of computation in the consideration of performance in planning and design. Since long, a building no longer simply serves to shelter human activity from the natural environment. It must not just defy natural forces, carry its own weight, its occupants and their possessions, it should also functionally facilitate its occupants’ activities, be aesthetically pleasing, be economical in building and maintenance costs, provide temperature, humidity, lighting and acoustical comfort, be sustainable with respect to material, energy and other resources, and so forth. Considering all these performance aspects in building design is far from straightforward and their integration into the design process further increases complexity, interdisciplinarity and the need for computational support.One of the roles of computation in planning and design is the measurement and prediction of the performances of buildings and cities, where performance denotes the ability of buildings and cities to meet various technical and non-technical requirements (physical as well as psychological) placed upon them by owners, users and society at large.This first volume contains 75 papers grouped under eleven subthemes that vary from Design Decision-Making over Spatial Performance and Space Syntax to Digital Fabrication.