In analysing parallels between sustainable and inclusive design, the paper investigates reasons for architects' disappointing uptake of these approaches so far. A common reason seems to be the lack of knowledge that has the applicability required by architectural practice. Researchers produce knowledge on why and how we should accomplish more sustainable practices in building, which hardly filters down to practicing architects. Vice versa, the knowledge developed through architects’ design experiences hardly feeds back into academic research. Moreover, in case of inclusive design, the user side represents a valuable body of knowledge as well: through their specific interaction with buildings/spaces, users with disabilities appreciate qualities and detect misfits most architects are unaware of. If the uptake of sustainability and inclusiveness in architecture is to be improved, the major challenge thus seems less a need to generate more knowledge than a need to make more effective use of what is already available.