The main goal of the project is to develop and validate a design solution, including construction technology, for carbon-neutral, modular apartment buildings that adhere to the principles of the circular economy. The project outcome will be a unique prototype of a modular apartment building and a validated construction technology. The baseline solution will be a timber structure, optimized and thoroughly evaluated in terms of environmental impact, supplemented with necessary technologies. In the final year of the project, all energy flows will be monitored and analyzed.