The starting point of the research is the need to refurbish existing residential building stock, in order to reduce its energy demand, which is a necessary step to reach the ambitious energy and decarbonisation targets for 2020 and 2050 that require an eventual reduction up to 90% in CO2 emissions. In this context, the rate and depth of refurbishment need to grow. The early design phases are particularly important, as decisions taken during this stage can determine the success or failure of the design. Even though the design decisions made earlier can have bigger impact with lower cost and effort, most existing tools focus on post-design evaluation. Therefore, the thesis aims at integrating the energy upgrade potential of residential façade refurbishment strategies in the early design phase, in order to support decision-making. Having available an assessment of the energy performance results in informed decisions that improve the efficiency of the strategy and the final refurbished building. This thesis concludes with an approach to enable informed and energy-efficiency conscious decisions in the early stage of the design of refurbishment strategies. To improve the design process, the Façade Refurbishment Toolbox (FRT) facilitates the development of strategies in different cases and for different specifications, without limiting or dictating designers’ choices. It consists of three different types of information that can support the decision-making of residential façade refurbishment strategies. Firstly, retrofitting measures for each building envelope component are proposed, composing the Façade Refurbishment Toolbox. Secondly, the measures are quantified in terms of energy upgrade potential. Finally, a roadmap to the key decision aspects in the refurbishment strategy development indicates when the toolbox information can be used. Designing is deciding. Knowledge and information can lead to better understanding of a decision consequent and, therefore, result in better design solutions. In this way, refurbishment strategies that take into account the building improvement, occupants’ comfort and efficient energy use can be designed, contributing to the greater society’s goals of CO2 emissions reduction and sustainable development.