Energy Performance of Ventilated Façades: Assessment of the Steady-State and Transient Calculation Approaches

The ventilated façade is a construction system that can prevent sunny façades from overheating. It can also be used on existing buildings as an energy rehabilitation system, which is so necessary to make the built environment more climate resilient. The usual systems used by architects to calculate the energy performance of the architectural enclosures consider the façade in nearly steady-state conditions, with an energy balance. In addition, they disregard the particularities of the ventilated façade. Therefore, they cannot give accurate information about the actual thermal performance of the façade. Thus, architects lack the tools to know, in a straightforward way, the real energy performance of the designed façade and how it is affected by different design decisions. The daily evolution of temperatures has been measured at different points of a ventilated façade. Also, a calculation system has been developed. It considers the defining parameters of the measured façade, the geometry of the environment, and the meteorological conditions. It can compute the ventilation of the cavity and the thermal performance, both in steady-state and transient conditions. In this presentation, the measured temperatures are compared with those resulting from the two types of calculation: steady-state and transient. The objective is to check which one is more appropriate in order to provide a reliable design tool for architects and designers.