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Is it more environmentally friendly to replace an existing building with a new one or to renovate the existing property? This paper addresses how to frame and evaluate this question. Although several previous studies exist, their methods lack a harmonised set of practice. A new framework is introduced that adopts the concept of consequential replacement framework (CRF) for life cycle assessment (LCA) which had previously been applied to vehicles. The application of the CRF to buildings is demonstrated with case studies on school buildings in Finland. Three alternative cases are examined: the refurbishment of a 1950s school; extending it with an annex; and demolition and replacement with a new concrete or timber building. As the European environmental impact regulation of buildings pertains to CO2 emissions, the paper also focuses on CO2. The case studies demonstrate that refurbishment in Finland is a more climate-friendly alternative to demolition and new build. The studied new buildings' better energy efficiency is set off for decades by the carbon spike caused by the embodied CO2 in their materials. The CRF is shown to be a methodologically sound, easily approachable framework for evaluating immediate environmental consequences of decision-makers' retention or replacement choices, suitable to different contexts. [ABSTRACT FROM AUTHOR]

Distributed electric power production by small-scale customers is increasing continuously. Photovoltaic production is a popular method of producing self-energy for customers. Additionally, power systems require more flexibility when weather-dependent renewable energy production increases. Small-scale customers can increase the self-consumption of self-produced energy by using batteries or a demand response operation. However, batteries require high investment, and demand response operations induce a loss of comfort. Customers who heat their buildings using electric heaters are a good target for demand response operations because their heating can be controlled with limited changes in the indoor temperature. The demand response potential of a building can be defined by simply using customer load profiles and knowledge of the outdoor temperature. Any other information is not required in the proposed novel method. A tolerable variation in indoor temperature corresponds to considerably smaller battery capacity, though it is still a significant amount. With an optimally sized photovoltaic system, it is possible to use both methods simultaneously to increase self-consumption. Maximal benefits can be attained from both methods if the battery system is used as a primary control and the demand response is used as a secondary control. The defined novel method for determining the demand response potential of small-scale customers can also be used when estimating the flexibility of a large customer group. Small-scale customers together can provide significant flexible capacity when their electrical heating is centrally controlled. [ABSTRACT FROM AUTHOR]

• Combination of digital technologies and EGD goals in built environment was studied. • Several policy instruments promote new technology. • Existing policy mix does not set clear targets for the digital transition. • Several individual supporting technologies exist but combinations are lacking. • Markets are not mature for twin transition solutions. This paper studies the implementation of twin transition, i.e., the combination of digital technologies and European Green Deal goals, to achieve sustainable solutions supporting the creation of impactful, net-zero carbon and a resilient built environment with a focus on Northern Europe, specifically Finland. The subject was examined from policies, technology and market perspectives. Numerous European regulations and policies are driving the twin transition since many of them include obligatory requirements for the member states. Technologies and technology combinations exist to support the twin transition in the Nordic built environment. It was assessed that energy technologies are the most important and control, monitoring and automation technologies are the second most important technology category for the twin transition. In addition, individual technologies' maturity and relevance to the twin transition in the built environment in cold climates were evaluated. By analyzing case studies, it was found that the markets are not mature enough to lead the twin transition, but external boosts are needed. However, this can also be seen as an opportunity for service business. The results are focused on Northern Europe, but European legislation also supports the international SDGs. [ABSTRACT FROM AUTHOR]

• This paper conducts assessment of hybrid renewable systems for urban buildings. • A new demand model for heterogeneous building types is developed. • Time series forecast of electricity market is proposed. • Novel renewable supply and balance scenarios are developed. • Techno-economic assessment of hybrid renewable systems shows feasibility. This research conducts a technical and economic feasibility study of multi-energy hybrid systems (MEHS) combining different renewables for a northern climate city of Finland to address issues of replacing fossil energy by renewable energy sources (RES) to achieve zero carbon emissions. The renewable energy systems MEHS include geothermal, biomass and solar energy. The selected city-study site is the Olympic Training Center occupied by heterogeneous buildings which presents a good representative urban city for the assessment of the energy supply and demand. A generic and integrated modeling framework grounded in a combination of novel forecasting models for the heterogeneous building energy demands, the splitting of space heating and hot water use, the coupled renewable energy generation, and the time series electricity market is developed to investigate optimal MEHS configurations based on the technical and financial analysis. Innovative scenarios of MEHS are developed. The analysis results show that MEHS can flexibly meet the energy demand for the heterogeneous buildings and the optimal configurations can be realised by an innovative integration of geothermal and solar sources as well as electricity as complementary energy. Model uncertainty and its impacts on the analysis are also considered and discussed. [ABSTRACT FROM AUTHOR]