The renovation of a building, instead of raising a new structure, is being scrutinized more closely at present as a sustainable alternative for reaping the benefits of improving a building's energy performance and mitigating its physical deterioration. The extent of the benefits would be dependent on the optimal renovation time determined through the building owner's decision-making process. Unfortunately, only a few studies have explored improvement of the decision-making process for determining an appropriate renovation time, making it difficult for building owners to conduct reliable cost-effective renovation planning. A model that estimates the optimal cost-effective renovation time of a building therefore would be a valuable tool, and the model introduced in this paper addresses this need. By applying the model to an actual renovation project as a case study, this model yielded 24 renovation alternatives for achieving a cost-effective renovation time, from which the optimal alternative was identified based on an economic analysis from the building owner's perspective.