GAIA Architects has been pioneering ecological design in Scotland since the early 1990s. Their philosophy, named eco-minimalism by their chief architect Howard Liddell, rejects the greenwashing of contemporary sustainable architecture in favour of simpler, more effective solutions. Through detailed scientific assessments of their projects, they were able to design buildings that aim to solve today’s most pressing issues of sustainable construction with the use of extremely low-technologies rather than the high-technologies commonly associated with “green” architecture. The first part of this thesis provides a description of the main aspects of eco-minimalism, useful to understand GAIA’s design choices and project outcomes. The second section outlines a selection of their most important and exemplificative projects, illustrating both the evolution and the recurrent sustainable features of their work.