Sustainable interventions in historic buildings: a developing decision making tool Chiara Bertolin 1* and Arian Loli 1 1 Norwegian University of Science and Technology (NTNU) - Department of Architecture and Technology, 7491 Trondheim, Norway * chiara.bertolin@ntnu.no Abstract Integrating multi-criteria approaches for reducing greenhouse gas emissions while, at the same time, ensuring long-term maintenance of existing buildings, is a challenge that needs to be faced by both the present and future generations. The core objective of this paper is to integrate a life cycle approach within the framework of building conservation principles to help decision makers dealing with “green” maintenance and adaptation interventions of historic buildings. The proposed approach identifies conservation principles to respect, it considers low, medium, high levels of intervention, and it analyses the impact of interventions in term of emissions and energy consumptions that should be compensated - while the historic building is in use - with on-site renewables. The method, in the whole, allows the comparison of different intervention scenarios and the selection of the most sustainable one over a long-term management perspective of the historic building. The benefits are twofold: under the conservative perspective, for helping in choosing the right time of interventions, in reducing the decay rate, in using materials that endure longer and are compatible with existing fabrics; under the environmental perspective, for helping in reducing the carbon footprint, in supporting conservation needs through a minimal intervention approach, and in encouraging materials reuse and renewable energy systems. Keywords: zero emission, historic buildings, maintenance, conservation, refurbishment 1 – Introduction Nowadays, the imperative to limit globally the concentration of Greenhouse Gases (GHG) in the atmosphere to 450 ppm [1], the Paris agreement [2] and the review of the Directive 2010/31/EU [3] on Energy Performance of Buildings by the European (EU) Commission, ask for larger reduction of the emissions in the building sector. In the cultural heritage sector, a historic building is defined as a single manifestation of immovable tangible cultural heritage in the form of an existing building that in addition manifests significance (i.e. historic, artistic, cultural, social and economic value). Historic buildings do not all have legislation protection or heritage-designation [4]. The heritage- designation of a building can be in the form of legislation protection i.e. “listing”, “scheduling” or inclusion in conservation areas or UNESCO World Heritage Sites. Depending on the form of designation, a heritage building can be referred to as “monument”. The majority of historic and heritage buildings has at least twice as long life spans of an existing building with no or low significance estimated in 60 years (i.e. standard life span (SLS)). They need appropriate high quality interventions to ensure satisfactory long-term performance and aesthetic continuity and are demanding sustainability mainly driven by environmental and economic reasons. Nowadays, efforts to achieve a “green label” for historic buildings in use, partially reflect the initiative of the individual heritage institutions, the national laws on the categorization of protected buildings, and the policies for implementing the use of renewable energy sources in different countries. In the future, cumulatively, for the stock of existing and historic buildings exceeding the SLS, the potential for reducing the CO2 emissions by systematically adopting decisions based on selection of environmental sustainable intervention options is huge.