The presentation of information to help homeowners make retrofit decisions has been identified as a major problem. While homeowners often depend on energy auditors and trade contractors as retrofit experts, information provided by them based on their knowledge, can be incomplete and even inaccurate. To the expert, knowledge is often implicit, usually committed to automaticity, and difficult to articulate. This research attempts to establish the determinants of expert knowledge in the home energy retrofit industry. Using literature review, Delphi, and nonprobability sampling techniques, 23 participants participated in the study. The findings identified key attributes of home energy retrofit experts. Based on these attributes, an expertise identification system, suitable for the selection of home energy retrofit experts was developed. The study contributes to understanding the role of expert knowledge generally and the home energy retrofit domain specifically and provides an effective metric for determining industry experts.