This project renovated a multi-dwelling building in Bulgaria from 1947, improving energy efficiency by 50% and comfort. Flexible financing allowed owners with low incomes to participate. Key renovations included insulating the exterior walls and roof, replacing windows, and improving the heating system. Monthly loan payments are partially covered by rents from new apartments created in the attic. Occupants are satisfied with reduced energy costs and improved living conditions extended the building's lifespan by 40 years.