Retrofit Challenge: Decarbonizing the Italian Residential Stock A replicable national strategy to accelerate renovation rates, depth and investment in existing residential stock applied to the case of Italy.

According to the IPCC and the science community in general, there is an urgent need to decarbonize the built environment in order to keep alive the possibility of achieving the goals of the Paris Agreement. Since 2015 when the targets were set, there have been different approaches and studies that show how decarbonization can be achieved, and many solutions exist nowadays to convert an existing building to net-zero and to design a new building as net-zero from the beginning. In the case of existing residential buildings, homes, the biggest problems still without solutions as of 2022, are related to accelerating the renovation rates, the depth of the renovations and solving how to incentivise the investment on retrofitting. The European Commision in October 2020, started a program called ‘The renovation wave’ as part of the ‘European Green Deal. It, established that in Europe buildings should reduce their emissions by 55% in 2030 and become net-zero by 2050. They set three priorities on their program: energy poverty and worst performing buildings, renovation of public buildings and decarbonisation of heating and cooling. Also determined that the average price of building renovation is around €100.000 per building. In Italy there are around 14 million residential buildings and so the total cost of retrofitting the existing residential stock will supposedly be roughly €1,4 trillions by 2050, of which €770 billions should be invested by 2030 if the 55% target is to be maintained. This investment will in most cases fall on the home owners, and so different strategies are already in place in terms of incentives by the Italian government, and many laws and regulations are currently being discussed to be updated in the near future. In the meantime, this research aims to create a national strategy based on the vulnerabilities that municipalities are facing, that could be replicated in other countries and focuses on tackling the three main problems mentioned: acceleration, depth and investment. Results aim to be useful for future local mitigation and adaptation action plans that need to be developed. The proposed methodology creates a comprehensible understanding of the climate projections by 2050; of the potential of small, under 5MW, solar and eolic power plants by municipality; of the stranding risk, the market value depreciation risk, that homes are facing in the country, by province; it creates an index of climate risk that rank vulnerability of all the municipalities; and explores also for each municipality, the optimal size for individual acceleration projects in order to fulfil the objective of decarbonization of the residential stock.