Increasing energy efficiency is a fast-track roadmap for carbon mitigation and improving buildings’ energy performance for achieving sustainable buildings. In Australia, the minimum energy efficiency standards have increased from 6 to 7 stars for new housing through the Nationwide House Energy Rating Scheme (NatHERS), which has progressively become mandatory for most states since 2023. Notwithstanding this policy effort, the latest data shows that most new houses (79.76%) have been still designed at the minimal compliance level without going 7 stars and higher, risking the industry blocking the pathway towards a sustainable future. Among other reasons, recent studies elucidate that this difficulty in going beyond minimal compliance is caused by building practitioners’ various compliance behaviours (i.e., attitudes towards going beyond minimal compliance, subjective norms, perceived behavioural control, and personal norms). This chapter investigates this compliance behaviour in Victoria—a pioneering Australian state in promoting sustainable buildings. From a questionnaire survey of 73 residential architects/draftspersons, builders, and thermal performance assessors, the chapter finds that building practitioners’ attitudes generally exhibit the lowest score while personal norms display the highest. Significant differences in attitudes and perceived behavioural control between building practitioners who work on volume homes and those who work on custom homes are shown. Strong variations in attitudes and personal norms are also demonstrated between thermal performance assessors and other occupations. Furthermore, distinctions in subjective norms among building practitioners with various lengths of work experience are presented. To facilitate the sustainable transition, interventions at improving attitudes should be introduced in the first place.