Energy life-cycle approach in net zero energy buildings balance: operation and embodied energy of an Italian case study

The paper starts from the results of one of the six case-studies of the SubTask B in the International EnergyAgency joint Solar Heating and Cooling Task40 and Energy Conservation in Buildings and CommunitySystems Annex 52, whose purpose is to document state of the art and needs for current thermo-physicalsimulation tools in application to Net Zero Energy Buildings.The authors extend the Net Zero Energy Buildings (Net ZEB) methodological framework, introducingthe life-cycle perspective in the energy balance and thus including the embodied energy of building andits components. The case study is an Italian building, tailored to be a Net ZEB, in which the magnitude ofthe deficit from the net zero energy target is assessed according to a life-cycle approach. The annual finalenergy balance, assessed with regard to electricity, shows a deficit which makes the case study a nearlyNet ZEB, when the encountered energy flows are measured at the final level. Shifting from final to primaryenergy balance the case-study moves to a non-Net ZEB condition, because of the large difference betweenthe conversion factors of photovoltaics generated electricity and imported electricity. The adoption of alife cycle perspective and the addition of embodied energy to the balance causes an even largest shiftfrom the nearly ZEB target: the primary energy demand is nearly doubled in comparison to the primaryenergy case.