The importance of individual temperature control in offices was established in the 1980s and 1990s. Unfortunately, the advantages of individual temperature control have not been realized well in practice, largely because of problems in the usability of thermostats. In this article, user interface prototypes for room temperature control were developed with a user-centred approach. Usability tests were conducted several times during the development process. As the definitive result of the work, usability guidelines for room temperature controls were developed. The usability guidelines help to design highly usable room temperature controls. The usability guidelines are: keep occupants in the loop; visibility, identification and reachability of temperature controls; shared temperature controls with heating and cooling systems; acceptable default settings; simplicity of interface; clear way to adjust room temperature; advice on comfortable room temperatures; clear and sufficient feedback after adjustment; fast effect on room temperature; adequate effect on room temperature; informative help; and aesthetic design.