%X To meet statutory carbon reduction targets in the UK, a radical transformation of existing building stock is needed. To achieve this, engagement of the practitioners involved in the Repair-Maintain-Improve (RMI) subsector – small builders and tradespeople - is essential. Previous attempts at investigating this topic have been atheoretical, presenting lists of drivers and barriers. Such lists are frequently arbitrarily categorised, limiting their usefulness to programmes of change. This study makes a novel contribution by applying an established model of behaviour change, the Capability, Opportunity, Motivation – Behaviour (COM-B) model, to a data set of 31 interviews with RMI practitioners in the UK. COM-B proposes that behaviour results from individuals possessing the capability to take action as well as the opportunity and the motivation to do so. The analysis identified capabilities including knowledge and co-ordination of people and resources; opportunities including state action and customer demand; and motivations including pride in work, maintaining a viable business, and co-worker and customer relationships. Recommendations are presented on the implications for policy. For successful transition to zero carbon homes, initiatives are needed to address the multiple factors which determine engagement in energy-efficient retrofit: capacities, opportunities and motivations. %A N Murtagh %A AM Owen %A K Simpson %J Proceedings of the Sixth International SEEDS Conference 2020 %O This version is the author accepted manuscript. For information on re-use, please refer to the publisher’s terms and conditions. %I Leeds Beckett University %L discovery10122873 %V 6 %S International SEEDS Conference %D 2020 %C Leeds, UK %B Proceedings of the Sixth International SEEDS Conference 2020 %T Beyond drivers and barriers: a theoretical framework addressing the engagement of UK construction practitioners in retrofit for energy efficiency