Environmental impacts (EIs) of building stocks have been receiving significant attention in recent decades as they consume more than 40% of the world's energy, release one third of total greenhouse gas emissions, and account for 30% of global landfill waste. Prior efforts have focused on mitigating EIs during the operation stage of buildings, while the environmental performance of other stages is relatively overlooked. Addressing this, whole-building life cycle assessment (WBLCA) has gained prominence from a life-cycle perspective to ensure the best environmental performance. However, there is an array of factors that can affect WBLCA results, and such uncertainties render decisions made for sustainable development untenable. Aiming to understand the comprehensive uncertain sources of WBLCA (what) and their corresponding solutions (how), this paper systematically reviews existing publications on WBLCA, presents its status and challenges, and analyses the taxonomy of uncertainties and eight uncertainty methods and variants thereof. Accordingly, a framework is developed that enables LCA practitioners to readily understand the correlation between WBLCA uncertainties and solutions, and conveniently locate and appraise them throughout the WBLCA process. Upon answering the known-what and known-how questions, this study contributes to the body of knowledge of LCA by providing a comprehensive and systematic methodology to evaluate the EIs of buildings.