A better understanding of general hindrances to the diffusion of innovations in the construction sector may help to improve the energy efficiency of buildings. This study uses a web-based questionnaire to collect information on Swedish architects’ perceptions of hindrances to the adoption of innovations in building construction. The responding architects characterise the Swedish construction industry as having a low level of innovativeness. The most influential hindrances to innovativeness were perceived as the focus on project costs instead of life-cycle costs, the economic risks that innovations imply, the focus on traditional engineering models, the construction industry’s tendency to use proven materials and methods, and contractors’ inability to adjust processes. In terms of the involved actors, construction clients were perceived to have the greatest influence on innovativeness, and stronger cooperation between the architect and construction client was recognised as important to facilitate innovativeness.