This study evaluates the environmental performance of an industrial ventilation system by conducting a lifecycle assessment (LCA) in accordance with ISO 14040/44 standards. Environmental impacts were quantitatively determined using the ReCiPe 2016 midpoint (H) method and cumulative energy demand (CED) indicators. System boundaries include raw material extraction, fabrication of galvanized steel ducts, transportation, installation, operation, maintenance, and end-of-life disposal. The results clearly demonstrate that the operating phase dominates the overall environmental footprint, particularly due to the electricity consumption associated with fan operation. Experimental measurements also reveal a direct link between duct airtightness, pressure losses, and operating energy demand. Improvements in joint sealing reduced air leakage by up to 55% in rectangular ducts and up to 75% in spiral-clamped ducts, especially when subjected to high static pressure. These reductions lead to lower fan power requirements, resulting in reductions in lifecycle energy use and environmental impacts. The findings confirm that duct sealing performance is a critical factor in the energy-environmental performance of ventilation systems. Improving duct airtightness is proposed as a cost-effective way to reduce operating energy consumption and associated emissions, and to improve system-level environmental performance in line with ASHRAE energy efficiency targets.