Residential buildings represent 60% of the building stock and the area where most of the potential to drastically reduce energy use and CO2 emissions lies. New directives push for deep retrofitting efforts, in order to achieve energy efficiency and RES adoption targets for 2020 and beyond. These require acting both on envelope and on energy use systems, mainly heating and DHW equipment that representing 51% of energy use in this sector. Frequently the upgrade of the envelope insulation is subject to constraints (i.e. historical centres, availability of space, need to relocate the tenants, costs and time issues) and acting on the heating plant is the only viable option. Currently solutions are not always suitable or cost effective in existing buildings (radiators, DHW, solar radiation in winter). Therefore to accelerate the improvement in energy efficiency and in the use of renewable energy in the residential building, a specifically designed solution needs to be made available. HEAT4U is an Industry led project whose main objective is to develop a Gas Absorption Heat Pump (GAHP) solution with efficiency on primary energy of 165% (EN12309) to allow a cost-effective use of renewable energy in existing residential building for heating and DHW services. The project is conceived to overcome a number of technological and non-technological barriers which currently prevent GAHP application in single family houses or small multi-storey buildings. HEAT4U main objectives are: -i) Development of Appliance with specifications suitable for the residential market (10 - 25 kW), ii) integration of the technology in existing heating and DHW architectures, iii) Development of a decision support system, enabling the optimal design in different building operating conditions, iv) Dissemination activity to promote the awareness of the benefits of the GAHP technology. The results will be demonstrated in 5 real cases'