C30 -- Sustainable Retrofit of Existing Buildings: A Comparative Study Between nZEB and Passive House Retrofitting Scenario PDF

Considering the ambitious goal for Climate-neutral building stock by 2050, the urgent need to decarbonize the built environment leads to sustainable retrofit measures for existing buildings. As carbon dioxide is emitted throughout a building’s lifespan, particular attention should be given to selecting the retrofit measures with regard to their environmental impact and their impact on the building’s energy performance. Within this framework, the current study investigates two retrofitting scenarios applied to an existing residential building that are shaped in order to satisfy the nZEB and Passive House requirements. The two frameworks were considered in order to compare the environmental impacts before and after the retrofitting of the examined building. A single-family building, located in Thessaloniki (Greece), was chosen as a case study. Initially, the energy performance of the existing building is assessed in order to draw conclusions about selecting the retrofit solutions. Two alternative retrofitting scenarios were developed, through a series of energy upgrading interventions. The nZEB retrofitting scenario includes the addition of thermal insulation on the building envelope, the replacement of windows with new ones, the replacement of the heating and DHW production systems with a heat pump, the installation of a cooling system and exploitation of renewable energy sources. Corresponding interventions are also proposed according to the requirements of the Passive House standard. The environmental impacts assessment based on the life cycle assessment method, including the retrofitting process, is conducted according to the considered scenarios. The comparison of the environmental impacts when the Passive House and nZEB retrofitting scenarios are applied provides an insight on how different frameworks affect the building’s environmental and energy performance. The results indicate that in the retrofitted building, the energy-based carbon dioxide emissions are reduced by 92.7% in the Passive House scenario and by 89.9% in the nZEB scenario, as compared to the existing building emissions.