Strategies for cost efficient refurbishment and solar energy integration in European Case Study buildings

•Comparison between energy efficiency by refurbishment and renewable energy.•Real European building projects under different climatic conditions.•Optimal measures in terms of energy savings and specific energy costs.•Higher specific energy costs for refurbishment in Southern European locations.•Solar thermal can be even cheaper than photovoltaics for southern locations.

There are numerous residential building typologies in Europe, which require differentiated strategies for building rehabilitation to obtain the lowest payback and highest energy savings. Building integrated renewables can provide some or most of the building energy demand with a strong dependency on climatic conditions. Within the project “holistic energy-efficient retrofitting of residential buildings” (HERB) in the European Union seventh framework program, the most appropriate way of saving energy and supplying building integrated renewables in 7 European countries is sought. This study presents an energetic and economic comparison between energy efficient refurbishment of the building envelope and the integration of renewable solar energy technologies for different climatic conditions.A range of dynamic multi-zone simulation runs were done in EnergyPlus increasing the thermal resistance of the building envelope elements from the national reference energy standard up to a low energy standard. For the given energy demand, the solar energy integration potentials providing electricity and heat are investigated using the simulation environment INSEL. Finally, cost analyses are done to find the financially optimum strategy for saving energy with building rehabilitation or producing energy with renewable technology integration.It could be shown that building rehabilitation becomes less cost and energy efficient with decreasing geographical latitude while renewable integration increases in relevance. Building insulation measures offer much higher savings than renewable production in more Northern locations even though with slightly higher specific costs. The measures suggested are now implemented in 12 building projects within the European project focusing especially on innovative materials and renewables.