In a context of fuel poverty, the application of cost-effective methodology for energy retrofitting of buildings is ineffective. In these situations, there is no energy consumption reduction and thermal comfort is hardly achieved. This paper introduces a methodology to choose the most appropriate retrofit measure in a context of fuel poverty. This methodology is based on thermal comfort as the main criterion, and secondarily, it is based on the budget for paying monthly energy bills and initial costs. This study demonstrates how thermal comfort and monthly available income of households must be the first criterion for decision-making process. The methodology has been applied in four buildings. Results demonstrate why active retrofit measures are ineffective when monthly budget to pay energy bills is reduced. In conclusion, recommendations are made to promote efficient public policies in energy retrofit. The study was supported by the European Regional Development Fund (ERDF) and carried out within the research project '{Re}Programa. (Re)habitation +(Re) generation +(Re)programming' during 2013-2015.