Sustainable architecture searches for methods to lessen the adverse environmental burdens of buildings by efficiently and moderately using materials, energy and space. Ensuring sustainable development in multiple dimensions requires an essential factor such as sustainable architectural practice that inculcates assessment framework. Life Cycle Energy Assessment (LCEA) is a key component of Life Cycle Assessment (LCA) in which energy use at different life cycle stage of buildings is the only parameter analysed. In developing countries, defining sustainable architecture and environmental sustainability assessment in buildings remains a herculean task. The aim of the study was to examine the theoretical challenges associated with defining what we mean by calling a building "green" or sustainable architectural design and a post-positivism viewpoint on sustainability assessment of architectural design. The objectives are to review the criteria for sustainable architecture and conduct an LCEA of an existing residential apartment building in Abakaliki-Nigeria, using process-based Life Cycle Energy Assessment. The embodied energy intensity was found to be high at 6.10GJ/M 2 , while cement-based component was 8.8% by mass but accounted for 67.6% of the embodied energy. Consequently, it is imperative to carry out LCEA at the early stage of design and employ strategies to reduce embodied energy instead of focusing only on lessening the operational energy. Environmental and energy efficiency approaches should be prioritized on a life cycle energy basis.