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June 17, 2026Open Access

Comparative Energy Consumption and Indoor Airflow Analysis of Four HVAC Systems in an Office Building Using Revit-Based Modeling and CFD Simulation

Key Points

To evaluate the energy performance and indoor environmental conditions of various HVAC systems in an office building.
Integrated framework using BIM, CFD, and energy simulation.
Analyzed four HVAC cases: VAV with DX, VAV with chiller, VRF, four-pipe FCU with chiller.
Annual energy simulations conducted as per ASHRAE Standard 90.1-2019.
Case 2 showed 41.5% lower energy consumption than Case 1, meeting ASHRAE benchmarks.
Case 4 demonstrated high operational flexibility with favorable performance.
Case 1 exhibited the highest energy consumption and lowest efficiency.

Abstract

Improving energy efficiency in office buildings is key to achieving net-zero carbon emissions targets, particularly in hot and humid subtropical regions where cooling demand dominates. This study suggests an integrated framework that combines building information modeling (BIM), computational fluid mechanics (CFD), and energy simulation to evaluate the energy performance and indoor environmental conditions of various heating, ventilation, and air conditioning (HVAC) system configurations in an office building in Taiwan. An office building was created with Autodesk Revit. Annual energy simulations were carried out in accordance with ASHRAE Standard 90.1-2019. Four HVAC cases were analyzed, including variable air volume (VAV) with direct expansion (DX), VAV with a chiller, variable refrigerant flow (VRF), and a four-pipe fan coil unit (FCU) with a chiller. The energy performance of the four HVAC systems was evaluated using energy use intensity (EUI), together with CFD analysis of airflow and temperature distribution in the occupied zones. The comparison showed that the system configuration had a clear influence on overall performance. Case 2 produced the lowest EUI, with annual energy consumption 41.5% lower than that of Case 1, and its performance met the ASHRAE benchmark. Case 4 also showed favorable performance with high operational flexibility, while Case 3 showed intermediate efficiency. Case 1 demonstrated the highest energy consumption and lowest efficiency. CFD results under the prescribed boundary conditions indicate that the simulated occupied zones maintained acceptable temperature and airflow distributions. The findings show that chiller-based HVAC systems perform more effectively than DX-based systems in subtropical office buildings. The BIM–CFD–energy simulation framework developed in this study provides a useful basis for early-stage HVAC system comparison and selection, particularly for energy-efficient building design in high-cooling-demand climates.

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