Multi-objective optimization analysis for high efficiency external walls of zero energy buildings (ZEB) in the Mediterranean climate

Abstract \{ZEBs\} in Europe adopt a technology of light multi-layered walls by using structural materials with low density, thermal isolation, wide thickness, low specific weight, low mass accumulation, to achieve very low steady thermal transmittance. These techniques work toward bringing down winter heating costs. In the Mediterranean area, the thermal overload is irreversible when radiation is not controlled and the free supply of heat indoors is mismanaged. The characteristics of multi-layered walls do not yield typical passive heating system benefits because there are not large surfaces with thermal accumulation mass that are capable of storing heat when necessary, and discharge it once the effect of solar radiation is exhausted. A multi-objective analysis is key to obtaining several types of high energetic efficiency external walls for \{ZEBs\} in the Mediterranean climate, through the combination of various materials. The analysis is carried out in terms of steady thermal transmittance, periodic thermal transmittance, decrement factor, time shift, areal heat capacity, thermal admittance, surface mass, thickness. The results show that the superficial mass of the external wall has important to obtain the best performance in the warm climate. It is possible to reach high performance in the summertime also by lighter and thinner walls.