To mitigate environmental impact and optimize energy consumption, it is imperative to construct buildings that are energy efficient. Despite this, many building defects compromise energy performance, resulting in higher energy demands, increased running costs, and higher carbon emissions. The objective of this study is to identify the major building defects that cause energy inefficiency and analyze the core causes of these defects. This study was done by a qualitative method that focuses on key point searching, analyzing, and synthesizing pertinent research data. Databases such as Scopus and Web of Science were analyzed through descriptive and content analysis methods. The key to searching for the major defect includes inadequate insulation, air leakage, thermal bridging, low-quality construction materials, and improper HVAC system installation. According to this key search data, the poor workmanship, noncompliance with building regulations, and inadequate quality control during construction are the primary factors contributing to the current defect issue. Furthermore, this investigation highlights the importance of enhancing stakeholder awareness, adopting innovative construction practices, and implementing stricter regulatory enforcement to improve the sustainability and energy efficiency of buildings. The outcomes of this study provide a foundation for future studies and regulatory changes that might lead to stricter building codes and encourage more environmentally friendly building practices.