This paper describes the application of a building simulation program to construct a decision-support tool for use by policy makers addressing the needs of the Scottish domestic housing sector. The process of tool formulation is described and an example given of its use to identify best-value retrofit options while taking factors such as future climate change and improved standard of living into consideration. It is argued that the process of tool formation renders it applicable to the cumulative roll-out of upgrade measures in the long term, both within and outwith the UK
