Cost-optimized energy-efficient building envelope measures for a multi-storey residential building in a cold climate

In this study we analyse cost-optimal building envelope measures including insulation for attic roof, ground floor and exterior walls, and efficient windows and doors for new buildings. The analysis is based on a multi-storey building in south of Sweden with an expected lifetime of at least 100 years. We integrate dynamic energy simulation, total and marginal economic analysis, and consider different scenarios of real discount rates and annual energy price increases. Our analysis shows that cost-optimal thicknesses of insulations for the building envelope elements are significantly higher than those required to meet the current Swedish building code’s minimum energy requirements. For windows, the cost-optimal U-value is about the same as required to fulfil the minimum requirement of the Swedish building code. Overall, large energy and cost savings are achieved when the cost-optimal measures are cumulatively implemented. Compared to the reference, annual space heating reduction of 28-43% is achieved for the building with the cost-optimal measures under the analysed period of 50 years. The cost savings varied between 21 and 188 k€.