The paper presents a study on the behaviour of solar walls in a residential building under a Mediterranean climate, in terms of energy performances and thermal comfort all year round. The aims of this study are: the investigation of Trombe wall's thermal behaviour; the evaluation of solar wall's influence on heating and cooling energy needs and indoor thermal comfort; the analysis and optimization of solar wall's behaviour in an accommodation varying the envelope insulation level. In order to do that, various activities were carried out: a series of monitoring campaigns in different seasons; dynamic simulations with software EnergyPlus; calibration of the model with experimental data; parametric analyses on the interaction between solar walls (on the southern side) and different types of building envelopes (on the other exposures) varying the insulation level according to recent standards. The results demonstrated that solar wall provides heating energy savings and thermal comfort in winter and intermediate seasons. A significant improvement of the solar wall's performances can be obtained using double glazing. In summer solar walls determine an increase in cooling energy needs and risk of overheating. The use of solar wall's shading and ventilation reduces such drawbacks and leads to indoor conditions within comfort range. (C) 2011 Elsevier B.V. All rights reserved.