In the early stages of building renovation projects, the lack of information on the existing building and an unclear definition of project objectives have been identified as critical bottlenecks. An early decision support tool has been developed to mitigate or overcome these barriers. The tool provides initial estimates tailored to the specific building and climate being assessed, and can be used to guide the renovation design at an early stage, even from very limited information. It includes the automatic generation of potential renovation scenarios, a dynamic energy simulation of existing and renovated cases, integrated economic and environmental assessments from a life cycle perspective, and a multicriteria analysis that ranks renovation alternatives to meet the interests of the stakeholders involved. The user obtains an initial indicative budget and the expected potential benefits of several renovation projects over comfort, energy consumption, economic cost and environmental performance. One of the main assets of the tool is the reduction in time and cost at initial phases of the renovation process, avoiding the need of site visits and the use of more laborious simulation tools.