Eco-Friendly Building Envelopes: Thermal, Energy, Cost and Time Performance of Prefabricated Lightweight MRC Panels in Residential Construction

The construction sector remains one of the largest energy users worldwide, with a significant portion of its demand coming from space heating and cooling. Since the building envelope controls the transfer of heat between indoor and outdoor spaces, improvements in wall, roof and floor systems are key to increasing energy efficiency and reducing operational emissions. In this context, traditional reinforced concrete (RC) frame buildings with brick infill walls continue to dominate residential construction in many Mediterranean countries. Although common and readily available, these systems often rely on multiple separate layers to provide structural stability and thermal insulation, which can increase construction complexity, thermal transition risks and variability during construction. At the same time, industrialized prefabricated systems, including lightweight micro-reinforced concrete (MRC) panels are emerging as promising alternatives for both structural and envelope functions. This study evaluates the thermal, energy, cost, and construction-time performance of prefabricated lightweight micro-reinforced concrete (MRC) panels – a type of EPS-core shotcrete sandwich system – as an alternative to traditional RC frame construction with brick infill walls. A comparative case study of a two-storey residential villa is conducted, combining energy analysis, cost assessment, and construction time evaluation. Results show that the MRC system reduces wall U-values by nearly 50% and lowers annual primary energy demand by approximately 14.7%. Construction time is reduced by about 19%, while initial costs increased moderately (≈2.8%). The findings highlight that while MRC panels improve envelope performance and construction efficiency, overall energy gains remain constrained by other envelope components, particularly the ground floor. The study supports a system-level approach to building design, where prefabricated solutions are integrated within a broader optimization framework.