###### Abstract  
In line with the Paris Agreement, Norway aims for an up to \(55\%\) reduction in greenhouse gas (GHG) emissions by 2030 compared to 1990 levels and to be a low-emission society by 2050. Given that 85-90% of today's buildings are expected to still be in use in 2050, refurbishment and adaptive reuse of existing buildings can help in achieving the environmental goals. The aim of this work is to provide a holistic picture of refurbishment and adaptive reuse of existing buildings, including buildings with heritage values, seen from a life cycle perspective. The methods applied are a literature review of LCA studies and experiences from quantitative case study analysis of selected Norwegian case studies. The findings show that extending the service life of existing buildings by refurbishment and adaptive reuse has significant possibilities in reducing GHG emissions, keeping cultural heritage values, and saving scarce raw material resources. The findings show limited LCA studies, uncertainties in existing LCA studies due to variations in case-specific refurbishment or intervention measures, and a lack of transparent and harmonized background data and methodological choices. In conclusion, performing a holistic study covering the whole LCA and including socio-cultural values and economic aspects will enable supporting an argument to assert the sustainability of existing buildings. emological emission; existing building; LCA; heritage value; socio-cultural value +
Footnote †: journal: _Sci._  
Footnote †: journal: _Sci. building stock is expected to follow the same trend. The construction industry is seen as essential in the transition to a circular economy, as it consumes around 40% of the total material resources and generates over one third of the total waste in the world [7]. The Norwegian national statistical data show that waste from construction, refurbishment, and demolition (1.95 million tons in 2019) represented around 26% of the total national waste, an increase by 5.6% from 2018 [8]. Of this, about 76.3% of the waste is from demolition and refurbishment activities, and only 46% of the total waste was recycled in 2018, which is a decrease of 8% from the previous year. To achieve the 55% emission reduction target by 2030, the EU should reduce buildings' greenhouse gas emissions by 60%, their final energy consumption by 14% and energy consumption for heating and cooling by 18%. The COVID-19 crisis has clearly demonstrated the importance buildings play in our daily life, and also the unique opportunities that lie in refurbishment in terms of rethinking, redesigning, and modernizing existing buildings into more energy-efficient and less material-intensive buildings and sustaining economic recovery [6]. Further, this is sustainable from a holistic and cultural heritage perspective, due to upholding and continuing the socio-cultural values the existing buildings, in general, and heritage buildings, specifically, represent. With the growing carbon spike and climate change impacts, refurbishment and adaptive reuse of existing buildings, and heritage buildings, can be conducive to taking immediate action and achieving various emission reduction goals. The EU Green Deal started a new renovation initiative in 2020, the \"renovation wave\", with a target to doubling the current public and private renovation rate in the next 10 years [9]. Applying circularity principles would help conserve scarce raw material resources, reduce GHG emissions associated with carbon-intensive production processes (i.e., cement, steel, and glass), and boost economic crises resulting from the pandemic. The evaluation of the environmental performance of existing buildings in a life cycle perspective, using transparent and harmonized methods, will enable avoiding problem shifting, and evaluating and following up the fulfilment of emission reduction ambitions.