Sustainability assessment of nearly zero energy renovation of dwellings based on energy, economy and home quality indicators

A case study of a Norwegian detached house is used to evaluate the sustainability of two nearly zero energy renovation strategies. Energy demand, life cycle cost and home qualities are assessed as sustainability indicators. The Façade renovation strategy is an energy upgrade of the façade supplemented with high renewable energy production on site. The Ambitious renovation strategy is a total building envelope upgrade using passive house components and a lower on site renewable energy production. Both renovation strategies result in a 50–85% reduction of the heating requirement depending on the renewable energy production. The sustainability assessment was done as an iterative process including qualitative and quantitative parameters. The Ambitious renovation strategy is more costly than the Façade alternative over a 30 year period. However, homeowners do not base their decisions to renovate strictly on cost evaluations and homeowner categories influence the assessment. The Façade strategy is suitable for homeowners that do the retrofit themselves and homeowners prioritizing to keep the existing architectural qualities of their house. The Ambitious strategy is more suitable for the homeowners seeking to change the aesthetics of their home as well as for the homeowners emphasizing the overall technical performance after renovation.

► Zero energy budget is possible after moderate renovation of the building envelope.
► Quantitative and qualitative sustainability indicators are used for the evaluation.
► The optimal sustainable renovation strategy depends on home qualities priorities.