Visualisation, the representation of data in visual form, is at the core of our ability to communicate information. Without clear representation, data would remain in its raw form thus greatly hindering the communication process. This is especially the case when the data source is large, complex and subject to change. One such area is related to the use of computer based simulation tools for thermal analysis. This research investigates the potential of visualisation to improve the ways in which thermal analysis data are presented to building services engineers, with a view to increasing the accuracy and efficiency of its interpretation. The approach taken throughout followed a pattern of research, development, demonstration and evaluation. The research phase included a detailed review of existing visualisation theory and an extensive user requirement survey. The development phase produced three working visualisation software prototypes, each of which was demonstrated or evaluated within the sponsoring company. Whilst the initial emphasis of the research was advanced Three-Dimensional (3D) visualisation, extensive user requirement analysis indicated that comparing multiple datasets in an intuitive manner was more important. In response, the research focused on combining techniques in ways which supported the rapid comparison of multiple files and the data contained within. The final prototype combines techniques for data storage and manipulation with information visualisation techniques and advanced 3D graphics. These elements are tightly integrated within a single application that facilitates the management and interpretation of data from multiple analysis models. Evaluation of the prototype showed high levels of user satisfaction and improvements in the accuracy and efficiency of data interpretation. The techniques demonstrated by the prototype were also understood and liked by the users of thermal analysis tools. Several of the techniques, such as the new Force Directed Difference Diagrams, have potential applications outside of building services engineering. The research has demonstrated it is possible to improve the representation and interpretation of building performance data using visualisation techniques.