Advancing building decarbonization via electrified thermal management: A VRF heat recovery system with domestic hot water integration

The building sector is responsible for a substantial share of global greenhouse gas emissions, making electrification with high-efficiency technologies a critical pathway toward achieving net-zero targets. Heat pump systems with heat recovery capability offer significant opportunities to reduce both energy consumption and carbon emissions by reutilizing waste heat within building thermal systems. This study evaluates a heat recovery–enabled Variable Refrigerant Flow (VRF) system integrated with a domestic hot water (DHW) loop through a hydraulic heat exchanger (VRF-Hy), designed to support fully electrified space conditioning and water heating. A quasi-steady system-level evaluation framework is developed and coupled with whole-building energy simulations using the DOE mid-rise apartment prototype model to quantify energy and decarbonization performance. The framework is applied to six representative U.S. climate locations, Miami (1 A), Tucson (2B), San Diego (3 C), New York (4 A), Seattle (4 C), and Denver (5B), to compare climate-dependent performance under a consistent building and control framework. Results show that integrating the DHW loop provides a stable heat sink, substantially increasing the frequency and magnitude of simultaneous heating and cooling operation and thereby maximizing heat recovery potential. Compared to a conventional baseline system, the proposed VRF-Hy configuration achieves simulated total annual site energy savings ranging from 31.1% to 50.4% and reduces equivalent CO 2 emissions by 31.0–50.3%, while completely eliminating on-site fossil fuel combustion. These findings suggest that heat recovery–enabled VRF systems with DHW integration offer a potential framework for building electrification and decarbonization. Unlike prior VRF-HR studies focused on component-level performance, this work provides a simulation-based system-level assessment of electrification and decarbonization impacts for the multifamily building prototype across multiple U.S. climate zones using a consistent whole-building modeling framework.