Commercial Air Conditioning: Duct, Rooftop, VRF and Air Handlers
Commercial air conditioning is not one product but several architectures, and choosing the architecture matters more than choosing a brand. This article compares duct, rooftop, VRF, cassette and air handler systems, and explains what each one needs from the buyer.
Duct systems: hidden, central, flexible
A duct system hides the indoor equipment in a ceiling void or plant space and delivers air through ductwork to outlets in each room. That makes it attractive for buildings where visible indoor units would clash with the interior — hotels, high-end offices, restaurants — and for buildings where one system should serve several rooms with a shared control strategy. The cost of that invisibility is ductwork: design, space, insulation, balancing and maintenance all become part of the project, and a poorly designed duct system can waste more energy than it saves. The commercial duct titles in this range are presented at title level only, with no airflow, pressure or dimension figures listed, so a duct buyer should send the building layout, the outlet count and the longest duct run in the first inquiry, and let the reply confirm whether a listed duct model fits. A capacity figure alone cannot confirm a duct system.
Duct systems also raise a zoning question. A single duct system with one thermostat serves all its rooms at one temperature, which suits open-plan spaces but frustrates buildings where rooms have different loads — a sunny side and a shaded side, for example. Zoned duct systems solve that with dampers and multiple thermostats, but they add cost and complexity. A buyer should decide the zoning strategy before choosing a duct model, because it changes the equipment and the controls, not just the duct layout.
Rooftop packages: one box, whole building
A rooftop package puts compressor, coils and fan in one box on the roof, with ductwork carrying air down into the building. That packaging simplifies the plant room — there is no separate indoor equipment to house — and it simplifies servicing, because the whole system is in one accessible location. It suits single-storey and low-rise buildings with flat roofs and available roof loading capacity, such as retail parks, warehouses with offices, and schools. It suits them less well when roof loading is limited, when roof access for a large unit is difficult, or when the building is tall and the duct runs from roof to ground floor become long and lossy. The rooftop title in this range is presented at title level only, with no capacity or dimension listed, so a rooftop buyer should send roof loading limits, duct routes and the capacity band in the inquiry.
Rooftop packages also concentrate noise and vibration on the roof, which matters for buildings with neighbours close by or with noise-sensitive rooms below the roof. The buyer should check local noise rules and the building's acoustic design before specifying a rooftop unit, because a rooftop location that looks convenient on a plan can become a noise problem in use.
VRF: many rooms, one outdoor system
VRF — variable refrigerant flow — connects many indoor units to one outdoor system and varies the refrigerant flow to each room independently. That architecture suits hotels, offices and apartment buildings where rooms have different loads at different times, because each room can call for its own cooling or heating without affecting the others. Some VRF systems also recover heat, moving heat from rooms that need cooling to rooms that need heating, which can save energy in buildings with simultaneous heating and cooling needs. Those are real advantages, but they come with design complexity: piping lengths, indoor unit combinations, diversity factors and control strategies all need careful design, and a VRF system designed badly performs worse than a simpler system designed well. The VRF title in this range is presented at title level only, with no combination table or piping figure listed, so a VRF buyer should send the room schedule, the simultaneous use pattern and the electrical supply, and should expect the design conversation to take longer than a single-unit selection.
VRF also concentrates risk: one outdoor system serves many rooms, so an outdoor failure affects the whole building rather than one room. A buyer should therefore ask about redundancy, service response and spare parts availability for a VRF system, and should weigh those answers against the flexibility advantage. A building that cannot tolerate a whole-system outage may need a different architecture, or a VRF design with redundancy built in.
Air handlers and cassettes: the remaining types
An air handler unit is the central air mover in a water-based or ducted system: it houses fans, coils and filters, and it delivers conditioned air to the building through ductwork. The R454B air handler unit in this range carries a full listed specification table, including capacities as listed, a 60 Hz supply, wired control and a thermostat, which makes it the most specified commercial model on this site. A buyer considering it should confirm the capacity steps — including the flagged capacity figure that is reproduced exactly as listed and must be confirmed before ordering — and should send the duct layout and control requirements with the inquiry. Ceiling cassettes, by contrast, suit open-plan rooms where a central ceiling panel serves the space from the middle, and the cassette category in this range is presented on the basis of the store's categories, with model details confirmed during inquiry. The choice among air handler, cassette, duct, rooftop and VRF is ultimately a building choice, not a catalogue choice: send the building facts, and the architecture will usually choose itself.