The paper presents low-tech and low-cost solutions such as, in particular, self-help retrofitting technologies, to improve the quality in spontaneous settlements (favelas) which arise close to the major Brazilian towns. In particular, a critical analysis of the favela Vila Novo Ouro Preto in Belo Horizonte has been elaborated, highlighting both social, cultural and technical aspects to design suitable technological components to be a dopted in order to improve environmental comfort.