The Energy Conservation Center Japan (ECCJ) conducted a workshop (ECAP 17) on the energy efficiency and conservation (EE&C) of buildings on 5–9 November 2018 in Tokyo, Japan. ECAP 17 was under the ASEAN Japan Energy-Efficiency Partnership (AJEEP), where Association of South-East Asian Nations (ASEAN) member states (AMSs) shared their knowledge and ideas to develop and implement building energy codes (BECs)/green building codes (GBCs) effectively in their home countries. This report summarizes the presentations, discussions, recommendations, and outcomes of the workshop.