A Critical Analysis of Research Gaps in Nearly Zero Energy Buildings

Nearly Zero Energy Buildings (nZEBs) are essential in sustainable construction, aiming to significantly reduce energy consumption and enhance the integration of renewable energy sources (RES). Given their critical importance in achieving global sustainability targets, this paper thoroughly reviews the existing literature on nZEBs, identifying notable gaps that may hinder their broader effectiveness and implementation. Through the application of cosine similarity and Term Frequency–Inverse Document Frequency (TF-IDF) methodologies, the exploration of research gaps in nZEBs reveals significant thematic intersections and divergences across five main research domains: renewable energy integration and optimisation; retrofitting and rehabilitation for energy efficiency; sustainable materials and technologies; analysis, optimisation, and modelling; and policy, economic, and social considerations. Demonstrating a general consensus regarding their significance, the findings indicate a high degree of thematic congruence concerning regional applicability, climate-driven optimisation, and incorporating advanced sustainable technologies. However, topics such as heat pump optimisation, ventilated roof desiccant systems, embodied energy considerations, nano-insulation technologies, and fuzzy cognitive mapping exhibit lower thematic congruence, indicating these as specialised and emerging areas that require further investigation and multidisciplinary integration. While lower cosine similarities reveal specialised and underrepresented subjects that present opportunities for future exploration, higher cosine similarities underscore critical, widely acknowledged research domains. This comprehensive examination of the subject emphasises the need for holistic, integrated strategies to achieve global sustainability objectives within the built environment while offering clear recommendations for forthcoming academic pursuits and policy formulation.