A life cycle energy perspective on the passive house concept

When low-energy houses are being built the focus is often to minimize the final (purchased) energy in the operation phase. However, the primary energy is more relevant when evaluating buildings from an environmental perspective. As the. energy for operation decreases, the relative importance of the other life cycle phases increases and influences an optimization aiming at minimizing the life-cycle energy use. We have studied the primary energy use for production and operation of four types of buildings, when using different types of energy supply systems for the heating. We show that a house from the 1970s after refurbishment and change of heating supply system had about the same primary energy use as a so-called passive house. The CO2 emissions were 64% lower, when a biomass-based heating system was used. We also illustrate the higher relative importance of the production phase for a building with low energy demand and efficient heat supply systems for operation.