Background Measures to increase the energy resilience of mountaineering tourism infrastructure are vital for the development of mountainous regions. Recent studies suggest important impacts of climate change on the energy sector and underpin the need for adaptation, notably in the electricity sector. Mountain huts are usually isolated from heating and electricity grids. They depend on fossil-fuel powered generators and boilers. Equipment and fuel is often supplied by helicopter, a costly means of transport and another source of CO2 emissions and pollution. The huts, being made of stone, are often highly energy inefficient. The development of energy-saving measures that significantly improve the sustainability and resilience of the off-grid mountain sector will contribute not only to the EU climate adaptation strategy but also to climate change mitigation, nature conservation and biodiversity objectives. In particular, achieving sustainable and nearly zero emissions mountain huts will bring biodiversity benefits due to the strategic zones where huts are located, including Natura 2000 network sites and biosphere reserves. Objectives LIFE SUSTAINHUTS aims to reduce CO2 emissions emanating from buildings in isolated environments, such as mountain huts. The project also aims to prevent air pollution, preserve mountainous forests, promote sustainable tourism and introduce environmentally-friendly methods for the production, distribution and use of energy. Specific project objectives are as follows: Creation of a resource assessment campaign adapted to extreme mountain conditions, measuring and evaluating the demonstration sites at micro level; Design and simulation of environmentally friendly off-grid renewable installations adapted to different mountain environments; Design of a complete off-grid hydrogen cycle, including an adapted electrolyser Balance of Plant (BOP), able to withstand critical water conditions of mountain environments, and a hybrid storage system; Integration of innovative and alternative technologies in mountain huts, such as hybrid storage systems and fuel cells to reduce fossil fuel dependency; Selection and installation of new-generation insulation materials that are more environmentally-friendly, have a low carbon cycle, increase the insulation capacity of the building by 10% of energy heat savings and are cost-competitive; Implementation and demonstration of nine nearly zero-emission demonstration mountain huts in four different European countries (involving different operational conditions of altitude and temperature):one demo-hut at low altitude (3,000m); Development of a life-cycle assessment of the huts to determine the environmental impacts of the new technologies compared with those currently used; and Development of guidelines for mountain huts and off-grid areas to promote the replication of results. Expected results: The project expects to achieve the following results: Transformation of nine mountain huts in four different European countries into sustainable, nearly zero-emission constructions powered by renewables: seven photovoltaic installations (35kW in total), three micro wind turbines (1.5 kW each), four micro hydro power plants (40 kW in total) and one hydrogen demonstration pilot system (3.3 kW off-grid electrolyser, high-pressure storage and 1.2 kW fuel cell); Carry out eight energy efficiency actions, including testing the thermal energy savings provided by three new insulation materials in the mountain huts; Reduce CO2 emissions by 21 tonnes/yr per hut; Reduce nitrous oxide (NOx) emissions by 500 kg/yr per hut; Reduce energy use by 20% per hut; Reduce by three the annual number of helicopter flights to the participating huts, saving 350 kg/yr of CO2; Reduce kerosene use by 1 tonne/yr per hut; A range of dissemination activities targeting high-level impact and international transferability, including a website, stakeholder awareness campaigns, participation in targeted events and four sets of guidelines (one containing project results and recommendations for policymakers, the other three being technical guidelines on the implementation of renewable energy systems and energy efficiency measures in mountain huts).