In this paper, the impact of a veranda (attached sunspace) on energy consumption is analyzed by numerical simulations (Clim2000 software) for two different configurations : a (existing) residential individual house and a (new) apartment building. The simulations are run by October to May (warm season). The model of veranda used in these studies is described with a focus on the calculation of the sun patch location. The main parameters are the lodging type and insulation (bad, average or very good), the veranda type (projecting or built-in), glazing (classical, strong insulation or low emissivity) and size, the separation between the veranda and the lodging (type and surface of the glazing part). The utilization of a veranda allows energy savings from 4% up to 23% with the best parameters and adds a comfortable room for autumn, best days of winter and spring.