LCE analysis of buildings – Taking the step towards Net Zero Energy Buildings

• LCE analysis of net zero energy buildings.
• The changing role of embodied energy.
• Important parameters to address in the context of a life cycle energy analysis.
• Annual energy savings achieved for Net ZEBs, clearly exceed the increase in embodied energy.

The basic concept of a Net Zero Energy Building (Net ZEB) is that on-site renewable energy generation covers the annual energy load.The main objective of this study is to analyse the increase of embodied energy compared to the decrease of the energy use related to building operation; partly by a literature review, partly by detailed analysis of eleven case studies; taking the step from a low energy building to a Net ZEB. The literature review shows that the metric of evaluation, assumed life-span, boundary conditions, age of database and the origin of database differ in different studies and influence the result of embodied energy. The relationship between embodied energy and life cycle energy use is almost linear for all cases studied herein. During the last two decades, embodied energy in new buildings has decreased slightly. However, the relative share of embodied energy related to life cycle energy use has increased. The detailed life cycle energy analysis show that taking the step from a low energy building to a Net ZEB results in a small increase of the embodied energy. However, the energy savings achieved in the annual operating energy balance clearly exceed the increase in embodied energy.