Brasilia is the designed capital city of Brazil inaugurated in 1960. Its plane like form has in its wings the residential sectors. Initially it was in its south wing the concentration of the residential buildings during its first years. Years later the building regulations changed and allowed for the newer residential buildings in the north wing sector to be larger and with a higher occupation. Consequently the urban building density of the north sector became higher than the opposite south sector. This reflected directly in the reduction of open spaces and greenery and consequently causing urban heat island effects. This paper compares both residential sectors and sheds a light on how new building regulations and construction are affecting the more recent buildings and interfering on the local microclimate and environmental comfort. Research included analysis of climatic data collected locally, urban morphologic studies, and computer simulations. The objective of this investigation was to see the effects caused by changes in design permitted by modified regulations in the two main residential areas of the urban plan of Brasilia. For two years, Romero’s research group analyzed 42 residential buildings, 22 in the north wing and 20 in the south wing. The data collected allows us to state that the later buildings constructed from the 90's are altering the local microclimate with a negative impact to its users, in contrast with the initial units built in the 60’s to the 80’s according to the original plan and regulations, with greater percentage of greenery.