Renewable and energy efficient solutions for heating and/or cooling, and domestic hot water production in multi-apartment residential buildings Proposals should demonstrate the cost-effective, heating and domestic hot water production units (including cooling, and/or complementary electricity production, where appropriate) installed in a multi-apartment residential buildings (above 6 apartments) or in a group of few similar multi-apartment residential buildings. This should include an assessment of the challenges and possible solutions to mixed tenure blocks, or owner occupier blocks, where one or more owners can potentially veto a viable scheme. The building envelope should already be renovated. The cost-effective integration of high performance heating and domestic hot water production should be demonstrated, together with calculation of fossil fuel reduction and primary energy savings. It is expected that the proposed solutions with all support systems will already have been validated in an operational environment prior to submission of the proposal (finished TRL 6, please see part G of the General Annexes) and properly documented in the proposal.The challenge is therefore to apply a new heating and domestic hot water preparation systems (optionally with additional cooling or electricity production as appropriate) and demonstrate their real performance in existing multi-apartment residential buildings with insulated walls and energy-efficient windows. A system should cover at least 70% of the total yearly energy demand of a building from renewable energy sources. In the proposal, the consortium should indicate the percentage of the total yearly energy demand of a building covered by the proposed system.The competitiveness in the building value chain and its position in growth markets should be elaborated. Proposals should pay attention to providing solutions to eliminate the risk of legionella for domestic hot water supplying unit a part of activities.The costs and energy benefit calculations, economic analysis including the worst case scenario, return of investment, and the comparison of the alternative solutions (including fossil fuels if used at selected demo sites) should be developed in a user-friendly manner suitable for convincing potential end users for a new system and to guarantee the project outcomes. Proposals should also contain estimates of values of capital costs, operating costs (including maintenance and inspection), pay-back time and system energy consumption. The system investment costs should be expressed in EUR, EUR/kW, and in EUR/kWh.The system should be scalable for different types of multi-apartment residential buildings and it is expected that at least three demonstration sites are placed in at least two European countries with different climatic zones. The demo sites’ energy consumption and the number of families in buildings differ at least by 80% among each successive installations to demonstrate their scalability. After the commissioning, the system should be run and monitored, for a proper time within the project duration (preferable one whole year), to assess its performance, system energy production, annual efficiency (the ratio between total system energy production and related energy consumption), etc.The developed system should have facilities to enable remote access, control and parameter settings from end user level. A dedicated application should be available and easy accessible/installed for each family premises to control at least in-house temperature with the possibility to modify the setting points. The entire system, including its control and monitoring functionality, should already be validated in operational environment before the submission of the proposal (at least finished TRL 6, please see part G of the General Annexes)Proposals should prepare service and repair manuals to support system assembly and installation and further end user’s instructions, assuring high quality and reliability of proposed systems. Proposals should also take into account the need for high indoor environmental quality (thermal comfort, acoustics, air quality, etc.).Proposals should aim at moving technologies from TRL 7-8 to TRL 8 (please see part G of the General Annexes). In all cases, the activities are expected to be implemented at Technology Readiness Level (TRL) 8 by the end of project activities (please see part G of the General Annexes).The Commission considers that proposals requesting a contribution from the EU of between EUR 2.0 and 2.5 million would allow this challenge to be addressed appropriately. Nonetheless, this does not preclude submission and selection of proposals requesting other amounts.This topic contributes to the roadmap of the Energy-efficient Buildings (EeB) cPPP. Taking into account that almost 50 % of Union’s final energy consumption is used for heating and cooling, of which 80 % is used in buildings[[DIRECTIVE (EU) 2018/844 OF THE EUROPEAN PARLIAMENT AND OF THE COUNCIL of 30 May 2018 amending Directive 2010/31/EU on the energy performance of buildings and Directive 2012/27/EU on energy efficiency)]], the achievement of the Union’s energy and climate goals is linked to the Union’s efforts to renovate its building stock by giving priority to energy efficiency. Buildings are becoming a factor in the generation of renewable energy and energy storage, but still the process should be accelerated.Renewable energy supply systems are not generally applied to their full potential and their application should be considered as a great opportunity to reduce fossil fuel consumption for existing multi-apartment residential buildings, regardless of their size, pursuant to the principle of first ensuring that energy needs for heating and cooling are reduced to cost optimal levels.There is a need to demonstrate the real performance (including economic performance) of innovative renewable and energy efficient solutions for heating, cooling and domestic hot water production in multi-apartment residential buildings and to provide information on the overall system performance to the end user.The analyses of existing building stocks demonstrate the high potential of renewable system applications in multi-apartment residential buildings, in which heating and cooling energy is currently supplied mostly with high valued energy sources e.g. electricity and fossil fuels. The implementation of renewable systems is lower than in single-family buildings due to several barriers. Proposals are expected to demonstrate the impacts listed below, using quantified indicators and targets wherever possible:Renewable energy production (in kWh /year);Primary energy savings and GHG emission savings triggered by the proposed solutions (compared to best available solution existing today);Competitiveness of the heat delivered by the proposed solutions (compared to best available solution existing today);To increase return of investment and reduce the pay-back time;Scale of the replicability and scalability potential of the proposed solutions.