Electric lighting energy consumptions of buildings and consequences in life cycle assessment

The paper, thanks to a significant case-study, discusses in details the influence of electric lighting consumptions on the entire life-cycle impact of a building. Energy, lighting and LCA simulations are carried out on a typical Italian office building during all its lifetime, considering both the design conditions and an alternative scenario, with a reduction of transparent surfaces. To avoid the shifting of the environmental impacts from one phase to another of the building life cycle, all the following aspects are being evaluated: the embodied energy of the construction materials and systems, their transportation and assembly energy consumptions; lighting, appliances, cooling, heating consumptions during the operating phase; energy consumptions related to materials and components end of life. The results show that the reduction of transparent surfaces increases electrical lighting consumption and the corresponding environmental impact, but moreover reduces the energy demand for air-conditioning, with the result that the overall life cycle impact decreases. Moreover the importance of materials choice is highlighted, since a different WWR (Window-Wall Ratio) may affect significantly the impacts due to the construction phase.