The ageing of buildings is associated with their degradation. By the end of a building's operative life, two solutions are provided: demolition and new construction, or renovation. New construction can cause higher greenhouse gas equivalent emissions than renovations, related to higher demand for building materials, processes, and waste management. Conversely, building renovation requires greater effort in planning and implementation. Moreover, when improperly planned, renovation might ensure only limited improvements in building performance. This study presents three renovation systems based on hybrid timber technologies for three common case-study building types in the Republic of Korea: apartment, low-rise residential, and mixed-use (industrial–commercial). Following analysis of the current regulations for building component performance in Korea, three modular building envelope renovation systems have been developed: (i) cross-laminated timber, (ii) glue-laminated frame with integrated timber stud panels, and (iii) steel frame with integrated timber stud walls. The development of the three systems focuses on designing modular self-supporting components that allow both horizontal and vertical extension, and the structural support of occupied buildings. The hybrid timber-based construction provides a low-carbon alternative to demolition and new construction, helping to solve spatial constraints to renovation determined by the high urban density of Korean cities. •Combining timber materials and BIPV facilitates carbon-neutral building renovation.•Research method addresses structural, technical, spatial, and environmental aspects.•Three modular building renovation systems with hybrid-timber technologies.•Load-bearing renovation and extension structures reinforce existing buildings.•Minimized Life Cycle Impacts and C02-equivalent emissions by extensive timber use.