The exterior envelope of some social housing scheme buildings constructed at the beginning of the 1970s without thermal insulation has proved to be the cause of great thermal loss and condensation. At the start of the 1980s, in order to resolve these problems, our research group carried out a study which led to the introduction of external thermal insulation (on the basis of previously developed performance specifications) and verification of the thermal performance achieved. With the aim of verifying the efficacy of the intervention after 20 years and in order to assess the thermal-hygrometric performance and the state of conservation of the exterior envelope we carried out a two stage study: 1. Performance analysis carried out through monitoring and laboratory tests. 2. Formulation of hypotheses for retrofitting, assessed through simulations and parametric analysis. The results showed the efficacy and durability from the thermal-hygrometric and mechanical point of view of the external insulation applied in the 1980s. It was also possible to verify energy saving for the different types of retrofit scenarios and to identify the correct positioning of the thermal insulation on the brickwork and on the floors so as to increase the surface temperatures in winter phase. (c) 2009 Elsevier B.V. All rights reserved.