Demonstrations serve an important role in the promotion of sustainable technologies. This paper analyzes sustainable building demonstration from the strategic niche management perspective. It studies how demonstration sequences conducted over a long time span gradually contribute to niche development for clean energy technologies at the national level. Our empirical analysis focuses on solar building demonstrations in Finland, an unfavorable context for the technology. Our findings show that the demonstrations leveraged sporadic windows of opportunity for the technology resulting from international developments. The projects supported three niche development processes: the building of networks, different types of learning and the creation of visions and expectations, thereby softening the ground for solar technology uptake in new buildings. However, they have also struggled to make an immediate impact on mainstream practices due to weak continuity and the challenging socio-technical environment. The paper concludes with implications for carrying out demonstrations projects that provide continuity in unfriendly environments.