A systematic review of energy retrofit measures in the building sector : cost, carbon and policy perpectives under EU frameworks

Abstract

A systematic literature review regarding energy retrofit measures in the building sector, financial modelling of retrofit measures, the most used types of energy retrofit measures, and knowledge gaps that could inform future studies. This study used PRISMA methods to rigorously screened literature published between 2014 to 2025, ultimately selecting 42 high-quality publications including peer-reviewed articles, technical reports, conference papers, and academic thesis from an initial 55 sources. Quantitative trend analysis completed in Excel and SPSS, evaluated publishing dynamics and knowledge gaps of energy retrofit studies. Study found that the dominate studied category was "envelope retrofits" which had an energy performance increase between 10%-95% with an average payback of 13.4 years. Moreover, envelope and heating system retrofits produced most financially favourable outcomes with heating system retrofits yielding 40.9% energy savings, 46.7% CO₂ emissions reduction, and a payback of 9.2 years. Additionally, control systems were found to produce the best financial returns at 1.7 years while producing only moderate increases in efficiency. Because of the moderate efficiency gains, control systems are recommended for early-stage energy retrofit initiatives as part of a larger integrated energy retrofit package to achieve the best long-term reductions (about 70%) in energy usage and associated CO₂ emissions. Nearly Zero-Energy Building (NZEB) strategies produced 72% energy and 77.5% CO₂ emissions, but the costs were €600 - €1,050/m² and the associated paybacks are generally significant. The best approach for executing an energy retrofit for residential and commercial building is a sequential phase approach using the energy retrofit strategy of quick-wins, system upgrades, envelope improvement, and deep retrofit as the applicable best practice.