Building stock renovation strategies for environmental and economic performance

Abstract

Building operation has a big impact on the environment, accounting for a large share of global final energy consumption and energy-related CO2 emissions. Renovation of the existing building stock is urgently required to achieve carbon neutrality by 2050.
The main goal of this study is the assessment of the current state of a Swiss residential building stock, provided by the Building Energy Performance Certificate of the Cantons (GEAK), and the identification of renovation strategies that are environmentally friendly and cost-effective. The proposed renovations concern building envelope renovation using conventional and bio-based insulation materials as well as substitution of oil and gas heating systems by more sustainable solutions, such as wood pellets boilers and heat pumps. Renovations are conducted gradually, based on the service life and previous renovations of building components and systems. A computational model is developed in python programming language that performs heating demand calculations as well as an integrated Life Cycle Assessment (LCA) and Life Cycle Cost Analysis (LCCA) for the renovated building stock. The proposed renovations are then assessed for compliance with the Swiss environmental targets stated by the 2000- Watt Society and by costs comparison with the non-renovated case. Finally, feasibility is examined in terms of resources availability for the possible heating system transformations.
The analysis shows that environmental targets are only achievable by elimination of oil and gas boilers, as replacement of those systems reduces substantially life cycle operational emissions. Implementation of bio-based insulation materials shows significant potential in reducing embodied emissions and is able to influence the LCA results if combined with appropriate heating system updates. From an economic perspective though, insulating the envelope as a sole measure is sufficient to reduce life cycle costs compared to the non-renovated case. Moreover, transition to wood boilers and particularly strategies involving complete envelope renovation are highly expensive solutions. Concerning resources availability for the proposed system transformations, the available wood in Switzerland is not sufficient to cover fossil supply, although substitution of oil and gas systems by heat pumps appears to be a feasible option. Overall, transition to heat pumps combined with sufficient envelope insulation demonstrates a good balance between environmental and economic performance of the building stock.