Life cycle energy performance evaluation

The majority of energy used in buildings has been traditionally linked to their operation (heating, cooling, lighting, etc.). Much attention has been directed to assess and reduce this energy use, and future refurbishment projects might aim for 'zero-energy' buildings. As this goal is progressively approached, buildings generally often employ an increasing amount of materials and systems, to the point that the energy associated with these, the so-called embodied energy, can constitute an important part of the building's life cycle energy use. For buildings achieving 'zero-energy' use in operation, the embodied energy is indeed the only life cycle energy use. Despite this, current building energy assessment methods, and strategies from approaching 'zero-energy buildings' or 'nearly-zero-energy buildings', frequently ignore the embodied energy component of building life cycle energy use. This chapter presents the concepts and methodology to evaluate life cycle energy performance of buildings, including embodied energy of the different components, systems and processes. It also introduces the concept of 'net energy ratio' (NER) to the built environment, presenting it as an indicator to support optimization of building refurbishment strategies from a life cycle energy perspective. A practical application is shown for the refurbishment of an Irish typical house.