One of the major challenges of building industry today is to provide indoor spaces allowing the occupants to make themselves comfortable while achieving low energy consumption. Considering the observed increasing temperatures and a more extreme climate, this becomes even more urgent and difficult to accomplish. It is therefore necessary to rely on approaches than contribute to sustainable building design, such as the adaptive approach to thermal comfort which postulates that people are not passive recipients of their environment but adapt behaviourally, physiologically and psychologically. The concept of adaptive thermal comfort was formulated many decades ago and has been validated in numerous field studies. Temperature thresholds based on adaptive models have been included in international and national standards. However, the overall understanding of how to translate the adaptive principles into design practice and concepts for operating buildings is still limited. Subtask B of IEA Annex 69 addresses this gap: “Strategy and practice of adaptive thermal comfort in low energy buildings”. The subtask aims to develop guidelines for low energy buildings that include the principle of adaptive comfort. This paper discusses the challenges and gaps identified in using the principles of adaptive thermal comfort in building design and operation and outlines the contents of the imminent guideline.