VRF vs Ducted Split System for Commercial Buildings

What You Need to Know

For commercial buildings that need air conditioning, the two most common system types are VRF (Variable Refrigerant Flow) and ducted split systems. Both use refrigerant to move heat, both connect outdoor units to indoor units, and both can cool and heat a building effectively. The difference is scale, zoning capability, and complexity.

A ducted split system connects one outdoor unit to one indoor fan coil unit, which distributes air through ductwork to the space. It serves a single zone with one thermostat. Capacity ranges from 7 kW to 28 kW per system, making it suitable for spaces up to approximately 200 to 300 sqm per unit. Multiple ducted splits can serve larger buildings, but each operates independently with no communication between systems.

A VRF system connects one outdoor unit to multiple indoor units through a network of refrigerant piping and branch controllers. Each indoor unit has its own thermostat and operates independently. A single VRF outdoor unit can serve 10 to 64 indoor units simultaneously, with total capacities from 14 kW to over 150 kW. Heat recovery VRF systems can heat one zone while cooling another at the same time, recovering energy that would otherwise be rejected.

The practical crossover point is around 300 to 500 sqm and 3 or more zones. Below that, ducted splits are simpler and cheaper. Above that, VRF delivers better comfort, lower running costs, and easier tenant or zone management.

• Refrigerant charge limits apply to both systems, but VRF carries significantly more refrigerant. A ducted split system typically holds 3 to 8 kg of refrigerant. A VRF system serving 20 indoor units may hold 30 to 60 kg. AS/NZS 5149 sets maximum allowable charges based on room volume, refrigerant type (R410A or R32), and occupancy classification. VRF systems in occupied spaces may require gas detection and mechanical ventilation interlocks where charge limits are exceeded. (AS/NZS 5149:2016)
• Minimum outdoor air ventilation rates must be provided regardless of system type. Neither ducted splits nor VRF indoor units introduce outdoor air on their own. A separate outdoor air system, whether a dedicated outdoor air unit, energy recovery ventilator, or ducted fresh air connection, must supply 10 L/s per person in offices, or the rates specified for other occupancy types. (AS 1668.2:2024)
• Economy cycles are mandatory for systems above 40 kW serving a single zone. Ducted split systems rarely exceed 28 kW individually, so this requirement typically does not apply. VRF systems commonly exceed 40 kW total capacity, and a dedicated outdoor air system or economy cycle provision is required to comply. (NCC 2025 Section J)
• Section J energy efficiency requirements apply to both systems. Pipe insulation thickness, ductwork insulation, fan power limits, and time switch controls must comply regardless of whether you install ducted splits or VRF. VRF refrigerant piping must be insulated to the same thermal resistance standards as chilled water pipework of equivalent diameter. (NCC 2025 Section J)
• All systems above 2 kW cooling must have programmable time switches. Both ducted splits and VRF must include time-based scheduling. VRF central controllers provide this natively. Ducted splits typically need a separate programmable thermostat or BMS connection. (NCC 2025 Section J)
• Refrigerant piping must be installed by licensed refrigeration mechanics. Both systems require an Australian Refrigeration Council (ARC) licensed technician for refrigerant handling. VRF installations are more complex due to longer pipe runs, multiple branch joints, and higher total refrigerant charges. Nitrogen pressure testing and vacuum holding tests are mandatory for both. (AS/NZS 5149:2016)

Consider a 1,200 sqm two-storey commercial office building in Sydney with six tenancies. The ground floor has a reception area, two separate office suites, and a server room. The first floor has three open-plan offices. Total cooling load is approximately 144 kW at 120 W/sqm. Here is how the two systems compare for this building.

Ducted split approach: You would install six to eight separate ducted split systems, one per zone. Each outdoor unit sits on the ground or roof, connected by refrigerant piping to its indoor unit in the ceiling void. Ductwork distributes air from each indoor unit to its zone. The server room gets its own dedicated system running 24/7 while the office systems run on business hours only. Total installed cost would be approximately $180,000 to $300,000, or $150 to $250 per sqm. Each system is independent, so a failure in one zone does not affect the others. The downside is eight separate outdoor units taking up space, eight sets of ductwork runs, and no ability to share capacity between zones.

VRF approach: You would install two or three VRF outdoor units on the roof, connected via a refrigerant piping network with branch controllers to 12 to 16 indoor units (cassettes, ducted, or wall-mounted) across both floors. Each indoor unit has its own thermostat and can be individually scheduled. The VRF central controller manages all zones from a single interface. Total installed cost would be approximately $300,000 to $540,000, or $250 to $450 per sqm. The system costs 60 to 80% more upfront, but you get individual zone control, centralised scheduling, and heat recovery.

Energy efficiency: The VRF system with heat recovery can transfer rejected heat from zones that need cooling (south-facing offices in winter, server room year-round) to zones that need heating (north-facing offices on cold mornings). This heat recovery capability can reduce energy consumption by 15 to 30% compared to ducted splits running independently. A ducted split rejecting heat from the server room wastes that energy entirely, while a VRF heat recovery system redirects it to warm other zones at almost no additional energy cost.

Zoning and comfort: With ducted splits, each system serves a single zone controlled by one thermostat. If one office suite is 200 sqm with both perimeter and interior spaces, the thermostat averages the temperature across the zone. Perimeter spaces near windows may be too warm while interior spaces are too cold. VRF places an indoor unit and thermostat in each discrete area, so the perimeter cassette ramps up while the interior unit modulates down. In a multi-tenant building, this granularity is essential for tenant comfort and energy billing.

Ceiling void requirements: Ducted split systems need ductwork from the indoor unit to every supply and return air grille in the zone. For a 200 sqm zone, the main supply duct may be 400 to 600mm wide and 250 to 300mm deep, plus branch ducts to each diffuser. This requires a minimum ceiling void of 350 to 450mm. VRF ducted indoor units also need ductwork, but because each unit serves a smaller area, the duct sizes are smaller (200 to 400mm wide). VRF cassette units need no ductwork at all, requiring only 250 to 300mm of ceiling void for the unit itself. In buildings with limited ceiling height, VRF cassettes can recover 100 to 150mm of usable space compared to ducted splits.

Multi-storey considerations: VRF refrigerant piping can run from a rooftop outdoor unit down through a riser to indoor units on each floor. Maximum piping length from outdoor unit to the furthest indoor unit is approximately 165 metres, with a maximum height difference of 50 to 90 metres depending on the manufacturer. This makes VRF suitable for buildings up to about 10 to 15 storeys. Branch controllers are typically located in the ceiling void on each floor, requiring access panels for maintenance. Ducted splits are limited to shorter pipe runs, typically 30 to 50 metres maximum, which means outdoor units must be located on the same level or one floor above/below the indoor unit. For multi-storey buildings, this often means outdoor units on each floor's balcony or louvred enclosure rather than consolidated on the roof.

Maintenance and lifecycle: Ducted split systems are simple to maintain. Each unit has one compressor, one fan motor, and a filter. Any refrigeration mechanic can service them, and replacement parts are widely available from multiple manufacturers. A ducted split system has a typical lifespan of 12 to 15 years. VRF systems are more complex. The outdoor units contain variable-speed compressors and sophisticated controls. Branch controllers, electronic expansion valves, and centralised management systems all require manufacturer-trained technicians. Replacement parts are manufacturer-specific and lead times can be 4 to 12 weeks for compressors. VRF systems have a typical lifespan of 15 to 20 years, partly because the variable-speed compressors run at part load most of the time rather than cycling on and off.

Section J compliance: Both systems must meet the same energy efficiency requirements under NCC 2025 Section J. However, VRF systems generally achieve better energy performance due to inverter-driven variable-speed compressors operating at part load, heat recovery between zones, and precise zone-by-zone temperature control. For JV3 energy modelling assessments, VRF systems typically demonstrate 10 to 25% lower annual energy consumption than equivalent ducted split configurations, which can help achieve compliance in buildings that are marginal under the Deemed-to-Satisfy pathway.