In the EU, there is a huge energy efficiency (EE) potential in the residential multi-apartment building stock. 1/3 of the EU’s buildings are over 50 years old with only very few (ca. 1%) being renovated each year. These buildings are not, in general, professionally managed. The renovation decision is complicated due to multiple apartment owners, insufficient information on the current energy profile and potential benefits of the renovation. The concept of EE renovation support exists in a form of one-stop-shop (OSS), which is a virtual and/or physical place where building owners can find all information and services they need to implement an ambitious global energy renovation project. Project partners identified that in their countries OSS as a complete system rarely exists, but different services that belong to the OSS are offered in a fragmented way. It means that the flow of OSS services that would otherwise engage and support the homeowner step by step from the start to the end of the process, is not provided according to the logic of the renovation journey, and the homeowner either stops in the middle of the journey or finds it difficult to even start it. The project develops One-Stop-Shop (OSS) extended model specifically designed for the multi-apartment buildings in BSR countries. The OSS model includes traditional and additional OSS services that cover all the steps that are necessary to initiate and implement EE renovation projects in multi-apartment buildings.