Abstract
The energy performance of buildings depends on the behaviour of the different components under transient conditions, as it happens in particular for the opaque envelope both through its stationary and through its dynamic response to the external solicitations. Some attempts to improve especially the summer performance of such elements are related to the insertion of air cavities, both still air or naturally ventilated through external openings. In those cases the annual performance evaluation becomes quite difficult, in particular when quasi steady state approaches are considered. A large number of papers in the literature consider theoretical and experimental analysis of different ventilated components (opaque ventilated walls, roofs, double skin facades, ventilated floors). Daily and annual variations of boundary conditions and their dependence on the specific climatic context further increase the generalization of the results. Summer improvement of comfort conditions and the reduction of cooling energy needs should be compared with the possible drawbacks during the heating season. This evaluation requires us to consider the entire building envelope and can be generalized only by means of a parametric analysis of the cavities impacts in relation to the composition, geometry, orientation and climatic context both of the cavities and of the building envelope. In the present paper a thermal and fluid-dynamic analysis of ventilated air cavities is performed under different flow patterns and external conditions. The aim is to analyse the impact on the energy performance of the opaque building components. The values calculated by means of the enhanced model are compared with the predictions obtained with the reference standards.