Energy retrofit of a single-family house: life cycle net energy saving and environmental benefits

When a building undergoes a retrofit project, the goal of assessing energy and environmental performances of retrofit actions is a complex matter. Building and its environment are complex systems in which all sub-systems are strongly interdependent and influence the overall efficiency performance. In the following paper, starting from a literature review of building life-cycle studies, the authors highlight that there is a strong interplay among all the phases of a building life-cycle, as each one can affect one or more of the others. In detail, starting from the results of a "cradle to grave" life cycle study of an existing Mediterranean single-family house, a set of retrofit actions voted to reduce the energy consumption during the operation is analysed. The proposed actions are addressed to improve the thermal performance of the building envelope and the energy efficiency of technical equipment. Performance assessment of these actions has been carried out not only considering the related effects on energy saving for building operation, but also taking into account other phases of the life cycles. In fact, these measures will cause an increase in the building embodied energy, which is the energy embedded in building materials, utilised in transportation and construction processes, in maintenance and demolition. Thus, a balance between the energy saving during operation and the avoided environmental benefits due to the other phases has been done. In particular, the embodied energy and the environmental impacts related to production, transportation and installation phases of the required material/components for retrofit implementation are assessed. In other terms, LCA allows to estimate the reduction of the operation energy and the increase of the embodied energy within the building life-cycle, and to understand whether the achieved energy benefits could be supported in a life cycle perspective or were overcome by the environmental burdens of the actions.