This four-part series by Eamonn Ryan explores how Variable Refrigerant Flow (VRF) systems are transforming HVAC design amid the global shift to low-GWP refrigerants and stricter energy standards. Drawing insights from ASHRAE experts featured in the ASHRAE Journal Podcast #52: ‘VRF Systems in an A2L World’, the series examines how innovation, safety standards, and international collaboration are shaping the future of climate control in commercial and residential buildings. This is article part two.
VRF systems have evolved in parallel with refrigerant technology. In North America, the widespread adoption of A2L refrigerants – a category of mildly flammable, low-global warming potential (GWP) substances – has presented both opportunities and challenges. Panelist Christopher William, an expert involved in revising ASHRAE Standard 15, explained that these refrigerants, such as R-32, feature low burning velocity and slow flame spread, which make them significantly safer than earlier perceptions suggested. Laboratory research and field trials have demonstrated that, even under ignition conditions, the refrigerants absorb heat and resist rapid combustion, which addresses safety concerns for occupied spaces.
The transition to A2L refrigerants has required careful updates to safety standards. ASHRAE Standard 15, originally established more than a century ago, governs the safe use of refrigerants in buildings. The standard has undergone a significant transformation, expanding from 18 pages to over 80 in recent years to accommodate modern refrigerants and systems like VRF. The revisions specifically address low-flammability refrigerants, detailing how they can be used safely in large-scale and distributed HVAC systems. “It took roughly 12 to 15 years to refine the language and safety protocols for A2L refrigerants,” William noted, highlighting the meticulous consensus-building process behind the standard.
The ASHRAE standards process involves multiple stages, including continuous maintenance proposals, committee and subcommittee debates, and public review periods. Public review allows stakeholders across the industry to comment, challenge or endorse proposed changes, ensuring that standards are robust, defendable and applicable in real-world scenarios. For VRF systems, this process has led to innovations in leak detection and safety. Modern fan coil units now feature refrigerant leak detectors and upstream safety shutoff valves. In the event of a leak, these mechanisms can isolate small amounts of refrigerant, preventing widespread loss, simplifying troubleshooting and ensuring safe, continuous operation.