The European ageing and inefficient residential building stock needs to be refurbished to achieve the targets relevant to energy efficiency and to secure healthy and comfortable living conditions. RECO2ST addresses the challenges of nZEB refurbishment through a systemic 3 step approach: Initially a Refurbishment Assessment Tool (RAT) will be deployed to create refurbishment scenarios, empowering the decision making of the building owner, public or private. Second, Action Plans for the renovation will be formed through Integrated Project Delivery (IPD) and finally a refurbishment package of innovative and customizable technologies will be installed (Retrofit-Kit) for personalized renovation. The Retrofit-Kit features cost efficient and modular technologies: Vacuum insulation (VIP), Modular Photovoltaics, Smart Windows with heating and cooling capacity, Wireless Sensor Networks (WSN), Intelligent Energy Management (IEMS), Nature Based Technologies (NBT) and optionally Cool Materials and Solutions. Their integration into personalized refurbishment packages for four demonstration sites will be conducted and validated. The renovation assessment tool and associated technologies will be demonstrated in four apartment block buildings (Spain, Switzerland, UK and Denmark) capturing climatic and construction variability across Europe, in total 67 apartments and 4900m2 of build space. The renovation assessment tool will tested on early adopter sites during the project. The modularity and adaptability of the RECO2ST Retrofit-Kit is key to achieving the expected performance and the Least-Cost method developed in the project will facilitate achieving this performance for the right price with a personalized renovation Action Plan developed quickly and accurately for each site under renovation. The demonstration sites will be refurbished into nZEBs achieving savings between 71 and 99%, with excellent internal environmental quality and payback in less than 15 years.