In terms of energy costs, the operation phase of the building is the most important. However, as buildings become ever more efficient in use, the construction and end-of-life stages grow in importance. To achieve Passivhaus standards of 15 KWh/m2/yr means employing large amounts of insulation and highly engineered construction products and sophisticated details. As a result, the construction and demolition im - pacts increase significantly compared to those of the building in use. Instead of the embodied energy required to manufacture the materials and construct the building accounting for 10 per cent of total energy use, the highly efficient green office may have 20 per cent of its total energy footprint contained in the construction and end-of-life phases. LCA allows these inter - actions to be better understood both at the initial stages of a building’s life and at any subsequent refit or major refurbish - ment.