In this study, we focus on a French program, named Mur Mur, introduced in the urban district of Grenoble in 2010 to increase the number of thermal retrofits in condominiums. This program (i) provides an energy assessment of the condominium and advices in terms of retrofitting to the co-owners and (ii) gives substantial subsidies to co-owners of condominiums that vote for a retrofit. To benefit from those subsidies, the majority of the co-owners of the condominiums simply have to vote in favour of and apply to the program, without any selection process. The only condition to be part of the program relates to the construction year of the building: condominiums must have been built between 1945 and 1975, i.e. before the first French thermal regulation. In this report, we have two objectives: first, identify the key variables in the decision to apply to the Mur Mur program; second, find out the main drivers of the decision to invest or not in thermal retrofitting for condominiums that applied to the program.