Abstract The paper aims to discuss the adaptation of a brazilian social housing project to the Passive House standard, by defining the thermal envelope construction fabric for different climates of southern Brazil, from a base line according to the Brazilian performance standard. The study was developed in 4 steps, where a numerical model was set up and runned in a transient regime, using EnergyPlus® software. In the first step, the thermal and energy performance of the reference base model was assessed. In the second step, a sensitivity analysis was performed, varying the thermal envelope parameters of the building case study, in order to satisfy the minimum performance of the classification level A, according to the Brazilian Energy Efficiency Regulation (RTQ-R). In a third step, the external envelope of the building was optimised, through a multi-objective evolutionary algorithm. In a last step, the numerical model defined according to the Passive House standard was optimised, in order to obtain optimal solutions. Thermal and energy performance and economic viability of the solutions were analysed. Solutions attending to RTQ-R presented additional investment between 26% and 27% and solutions attending to Passive House standard presented additional costs of 39% and 42% for the three bioclimatic zones.