Plug-and-Play Cartridge Facades: Assessing Energy, Carbon, and Cost in Office Renovations

Renovating existing office buildings is crucial to reducing energy demand and achieving carbon-neutral targets. Among retrofit options, building envelope renovation remains a highly effective way to improve efficiency. However, conventional renovation strategies generally emphasise basic façade improvements, such as window replacement, which may limit the achievable energy reduction. This study evaluates a modular plug-and-play (PnP) cartridge façade system developed to enable rapid installation, easier maintenance, and integration of building technologies in ageing office buildings. A representative office building in Seoul, completed in 1997, was analysed using five years of measured operational data (2020-2024). A calibrated simulation model was developed in OpenStudio and validated in EnergyPlus 24.1, achieving a 2.71% deviation from measured annual energy consumption. Two renovation pathways were compared: (1) a conventional sequential upgrade approach and (2) a smart façade-integrated renovation strategy incorporating modular cartridge systems. Performance was assessed in terms of energy use intensity, carbon emissions, operational energy cost, and life-cycle cost (LCC). The conventional pathway including insulation enhancement, window replacement, solar shading, lighting upgrades, and high-efficiency HVAC systems achieved a maximum energy reduction of 5.6%, lowering annual energy use from 305 to 288 kWh/m2yr. Carbon emissions decreased from 102.9 to 98.5 kgCO2e/ m2•yr (4.3%), and annual energy costs declined from 40.9 to 39.0 thousand KRW/m2•yr (4.7%). In contrast, the smart renovation approach produced greater reductions. A conventional double-skin façade reduced energy use by 18.1%, whereas the cartridge frame system achieved a 26.0% reduction. With adaptive louvre control, system upgrades, and integration of an air-handling cartridge with a Floor Terminal Unit (FTU), total energy reduction reached 36.8%, reducing consumption to 193 kWh/m2yr. Carbon emissions decreased to 71.4 kgCO2e/ m2•yr (30.6%), while annual energy costs declined by 29.1%. Although the cartridge façade required 14% higher initial investment than a double-skin façade, it achieved 29% lower maintenance costs and a payback period of approximately 12-13 years. These findings indicate that modular façade systems can provide a practical pathway for achieving deeper energy savings and improved long-term adaptability in existing office buildings.