The European Commission’s Renovation Wave strategy  states that “The Commission will introduce Digital Building Logbooks that will integrate all building related data provided by the upcoming Building Renovation Passports Smart Readiness Indicators, Level(s) and EPCs to ensure compatibility and integration of data throughout the renovation journey”.
A digital building logbook is a common repository for all relevant building data. Functioning as a dynamic tool that allows a variety of data, information and documents to be recorded, accessed, enriched and organised under specific categories . The purpose of this novel concept is to ensure all relevant data is stored and made available to various stakeholders to support their decision-making process. For the building owner, it can enrich a Building Renovation Passport (i.e. a renovation plan for the specific building) and improve the likelihood the renovation decision is well-informed in terms of economic, environmental and social parameters. It can improve circularity by enabling construction and waste companies to identify certain materials and effectively dismantle the building at the end of its lifetime. Furthermore, it can help local authorities to plan for carbon neutral (or positive energy) districts as the logbook comprises detailed information on all the buildings. The logbook can therefore allow the local authorities to more accurately match local energy demands with energy supply (e.g. how many buildings must be renovated for low-temperature district heating to be feasible in a specific district). The instrument can also be used to drive local collective decarbonisation efforts. For example, by aggregating demand for energy renovation solutions or renewable energy installations. Furthermore, the digital building logbook can also help local authorities to more easily and accurately monitor the mitigation progress of the building stock.
(Source: BPIE for Horizon 2020 project X-tendo, 2021 )
The sub-type benefits the Digital Building Logbook can bring to enable smart and sustainable cities, are several including,:
Drive local collective decarbonisation efforts. The decarbonisation efforts of buildings and cities need to become more harmonised for the EU to reach its long-term objectives. The Digital Building Logbook could be used to aggregate demand for renovations in a district, where renovation needs more easily could be identified. The Digital Building Logbook could be a useful tool in the transformation towards positive energy districts. 
Support local authorities. The Digital Building Logbook can be used to monitor the progress towards climate and sustainability goals. For example, it is used in Flanders (Belgium) to monitor the progress of the building stock towards the long-term target. Furthermore, the Digital Building Logbook could be used to support local authorities to develop better energy and climate plans, where the logbook provides detailed information about every buildings, including which measures are required in the future. 
Support local one-stop shops for energy renovations with data. Deep renovation is a complex process that involves a complete overhaul of a building. Most people are aware that better insulation of walls, roofs and basements will lower the energy consumption of the household but they have little information on what the benefits entail, who to contact, what measures to prioritise or which order they should be implemented. Digital Building Logbooks can enrich one-stop shops with data, enabling them to provide a stronger case for why the building owner should invest in an energy renovation. 
Facilitate circularity in the building sector. The Digital Building Logbook can enable circularity in construction and buildings through deconstruction, reuse and recycling of materials. The logbook can include information on which materials the building comprise and where these are places, which will facilitate a more effective recycling process. Furthermore, it can improve traceability of materials and chemical substances. 
Support the development of Building Renovation Passports. A building renovation passport provides a long-term, tailored renovation roadmap for a specific building, following a calculation based on available data and/or an on-site audit by an expert. The available data in the Digital Building Logbook allows for a more precise and cost-effective Building Renovation Passports to be developed. 
(Source: VEKA – Flemish Energy and Climate Agency. Illustration of their operational Woningpas, which is the main inspiration for the digital building logbook)
MATURITY: Look at sub-types of solutions.
The core of the Digital Building Logbook is the technical solution allowing it to integrate data from several different sources (existing databases, smart thermostats etc.) and enable different stakeholder to access sections of this data. The technological innovations are related to data governance issues, including data matching, storage and security. EU projects and frontrunner cases have shown it is possible to establish a logbook interconnecting different data sources. The Digital Building Logbook concept will be further developed under Horizon Europe (2021 call). Activities are expected to start at TRL 5 and achieve TRL 7 by the end of the project. The main hampering barriers relate to data governance issues (privacy, security etc.) and data ownership limitations.