Computational Fluid Dynamic Simulations of Natural Convection in Ventilated Facades

Abstract

The European Directive 2002/91/EC (Energy Performance of Buildings) aims to achieve minimum standards on the energy performance of new buildings and existing buildings that are subject to major renovation. To evaluate the energy performance of a building is necessary to calculate the energy required to satisfy the various services related to the standard usage of the building. In order to achieve the minimum standards for energy certification should be an approach to design alternative to the traditional one which allows to reduce significantly the building's energy requirements maintaining the level of indoor comfort. The energy needs of the building depend on the efficiency of envelope: when it was not designed and constructed correctly, the heat fluxes through the structures (vertical, horizontal, transparent, opaque) cause a large increase in final energy consumption. The heat exchanges depend on the temperature difference between the inner and the outer faces of the boundary element (horizontal or vertical) and the thermal resistance of the material (or combination of materials) that constitute the envelope and the contribute of solar radiation. In summer, especially during the days with high values of temperature and solar radiation, the building envelope should be designed and constructed so as to ensure adequate environmental conditions for thermal comfort in the indoor environment, even in absence of conditioning systems.