Renovation wave of the residential building stock targets for the carbon-neutral: Evaluation by Finland and Türkiye case studies for energy demand

The recent EU energy efficiency goals and renovation wave have called attention to the building stock's energy-demand-saving potential. Finland and Türkiye, with two contrasting perspectives on climate zones and building typologies in the EU, were chosen to analyse energy-demand potential. The study's scope was restricted to the residential building stock, a significant portion of the overall building stock. The latest residential building stock data and regulations history was gathered via a bottom-up approach. Then three representative buildings for each typology were energy demand simulated for climatic regions and periods. Thirdly, the area-weighted energy needs difference values for each decade (1960–2020) and climatic zone were multiplied with the building stock data to predict saving potential. Fourth, the impact of factors on energy demand was assessed using full-factorial analysis. Lastly, the main factors were parametrically simulated and compared with mandatory limits. The substantial energy-demand-saving potential existed in both countries. The findings highlighted the following: (1) the energy demand saving potential for the Finnish and Turkish building stocks were calculated as 10,176.9 GWh/year (30 %) and 124,889.3 GWh/year (50 %), respectively; (2) energy demand in Finland is dependent strongly on the climatic zone; (3) the optimum thermal insulation thickness for Finnish buildings is likely to be at the current level or even below it, while Türkiye's insulation limits are climatic zone based but not sufficient for carbon neutral; (4) Surprisingly for both countries, the most important factors to consider when renovating buildings were the thermal insulation level of the walls and roof in single-family buildings and the thermal insulation level of the walls in multi-family buildings and the airtightness of the building envelope. It should be noted that for Finland, building energy efficiency regulations will differ on the climate zone. Türkiye's newly published NZEB values should become mandatory lower limits for all residences because current legislative limits are insufficient and date back to the 2000s.