Development of an advanced methodology for assessing the environmental impacts of refurbishments

The refurbishment of the building stock is one of the key tasks for reducing the future environmental emissions in building sector. The assessment of the environmental impacts (EI) of refurbishments with LCA methodology remains a challenge. In the current practice, the refurbishment is threated as the beginning of the new lifecycle and all the impacts associated with the previous life cycle are generally neglected. The exclusion of materials and components used prior to the refurbishment produces a data gap at the end-of-life since information about materials that remained in the building after the refurbishment are missing. Furthermore, no information about what impacts have already been considered in the past bears the risk that some of the impacts are double-counted. In order to overcome these problems, an advanced methodology for the assessment of the embodied impacts in the case of refurbishment was developed that combines two sub-methodologies that can also be used separately. The first sub-methodology is used for remodelling the input data in order to make them time corresponding. The second sub-methodology is used for the assessment of the EI in the residual value of building materials and components and is including the allocation of EI between the life cycle before and after the refurbishment. The combination of the two sub-methodologies enables a more realistic and accurate assessment of the environmental impacts. The methodology is illustrated on the case on the case of a façade refurbishment. Five different allocation approaches are investigated and the residual value is calculated after a selected time period before and after the refurbishment. For all the inputs time-corresponding data is modelled and used. The study showed that for the life cycle before the refurbishment the EI and the residual value are generally higher if time-corresponding data is used since the EI of the electricity mix are higher. It turned out that the use of different allocation approaches is favouring either the use of recycled or reused materials or the recycling of the materials at the end. The PEF and the cut-off approach with module D are both enhancing the circular economy. It can be assumed that they are likely to prevail in the future.