A rooftop unit packages the compressor, coils, gas heat and blower into one cabinet that sits on a curb on the roof and drops a single duct connection through it. A split system separates the condensing unit outside from the evaporator and air handler indoors, joined by refrigerant lines. For a single-tenant box with a structurally sound flat roof, the RTU is the default and usually the cheapest path. Where the roof can't take the load, where tenants need independent zones, or where noise near occupants matters, a split or VRF system wins.
Rooftop Unit (RTU) — At a Glance
- All components (compressor, evaporator, gas heat, blower) packaged in a single cabinet on the roof
- Single duct connection through the roof penetration
- Typical capacity: 5 to 25+ tons cooling, 100k to 400k BTU heating
- Common in: strip malls, retail boxes, warehouses, single-tenant offices, light industrial
- Lifespan: 15–20 years
- Replacement cost: $14,000 – $48,000+ per unit installed, depending on capacity and roof access
Split System — At a Glance
- Compressor and condenser outside (ground or roof), evaporator and air handler inside (typically mechanical room)
- Refrigerant lines connect the two — installed by professionals only
- Typical capacity: 1.5 to 30 tons cooling depending on configuration
- Common in: multi-tenant offices, restaurants needing zone control, hotels, residential-converted-to-commercial buildings
- Lifespan: 15–20 years
- Replacement cost: $9,000 – $40,000 depending on size
The comparison in one place
- Where the equipment lives — RTU: entirely on the roof · Split: condenser outside, air handler in a mechanical room or ceiling space
- Floor area consumed inside the lease — RTU: none · Split: a mechanical room or a ceiling plenum
- Zoning — RTU: one zone per unit, so multi-tenant means multiple units · Split and VRF: several zones from one outdoor unit
- Heating — RTU: an integrated gas section in the same cabinet · Split: a separate furnace, boiler coil, or heat pump operation
- Service access — RTU: roof access for every filter change and every fault · Split: ground or interior access for most work
- Failure exposure — RTU: a major component failure often takes the whole packaged unit · Split: components replaced individually
- Free cooling — RTU: economizer dampers are standard on most commercial models · Split: rarely available without a separate ventilation system
- Replacement day — RTU: a crane and a curb adapter · Split: no crane, but line-set and interior work
That last-but-one row deserves a note, because free cooling is the RTU's quiet advantage in Ontario. Most commercial rooftop units carry an economizer: motorised outdoor-air dampers that bring in cool outside air instead of running the compressor when conditions allow. In a Toronto or Hamilton retail box with heavy interior lighting and refrigeration load, the building calls for cooling deep into the shoulder seasons — and an economizer covers a meaningful share of those hours on fan power alone. It is also the component most often found stuck, disconnected or seized during a first maintenance visit, which is why a building's energy numbers sometimes improve after nothing more than a linkage repair.
When RTUs Win
- Building has flat roof with structural capacity for HVAC equipment
- Single zone or simple multi-zone setup acceptable
- Want all equipment outside the leased space (frees up tenant area)
- Preference for simpler service access (everything on the roof)
- Short-term lease with multiple tenants — RTUs make zone changes simpler
When Split Systems Win
- Roof can't support an RTU (sloped, lightweight construction, heritage building)
- Multi-zone requirements with VRF (variable refrigerant flow) capability
- Lower noise requirements (compressors can be ground-mounted away from tenants)
- Custom airflow needs (industrial process cooling, server rooms)
- Heritage facade preservation — outdoor units can be ground-mounted out of sight
Free quotes, written pricing.
Variable Refrigerant Flow is the modern evolution of the split system: one outdoor unit serving 8–32 indoor units, each with independent zone control and inverter-driven capacity modulation. It costs more up front, delivers far better part-load efficiency, and gives every tenancy its own thermostat — which is why it keeps showing up in newer GTA office buildings and hotels. The lines to know are Daikin VRV, Mitsubishi City Multi and LG Multi V.
What replacement costs, and what the quote leaves out
- Single 10-ton RTU: $22,000 – $35,000 installed
- Equivalent split system (10-ton condenser + air handler): $18,000 – $32,000 installed
- 10-ton VRF with 8 indoor heads: $35,000 – $60,000 installed (higher capability)
- Crane mobilization for RTUs: $1,500 – $5,000 per crane day
The curb is the variable nobody budgets for. An RTU sits on a roof curb, and replacement units almost never match the footprint of the one they replace — manufacturers change cabinet dimensions and duct opening locations between generations. The usual answer is a fabricated curb adapter, built to bridge the old opening to the new unit, plus new roof flashing where the membrane is disturbed. That work is quoted separately from the equipment and it is where a cheap number turns into a realistic one.
The other schedule item is the crane. On a plaza off the QEW with open parking, a crane lift is a morning's work. On a downtown Toronto street or a tight Hamilton industrial site, it can mean a lane closure permit, an early Sunday, and traffic control — planned weeks ahead, not on the day the unit fails. Our commercial RTU replacement guide walks a property manager through the sequence.
What maintenance looks like on each
- RTU: every filter change, belt check and fault call means roof access, fall-protection tie-off in winter, and a technician carrying parts up a ladder or hatch
- RTU: cabinets sit exposed — condenser coils near the QEW and Red Hill corridors collect road salt and grit, and coils clog with cottonwood seed in June
- RTU: older units run belt-driven blowers, so belts and sheaves are a scheduled item; newer units are direct-drive with an ECM
- Split: the outdoor unit is at grade where a technician can work on it in February without a harness, and a bad condenser fan motor is a part rather than a capital decision
- Both: new equipment is shipping with A2L refrigerants, which brings leak-detection requirements and different service procedures — see the A2L refrigerant transition
Whichever configuration you own, scheduled service is what keeps a commercial system out of the emergency queue — our commercial preventive maintenance guide covers what a proper visit includes.
The decision rule
- Flat roof with capacity, one tenant, simple zoning — RTU. It is the cheapest to install and the simplest to replace.
- Roof can't take the load, or the building is heritage or sloped — split system, with the condenser at grade
- Multiple tenants who each want their own thermostat and their own bill — VRF, or one RTU per tenancy if the roof allows
- Restaurants, server rooms or process cooling with an unusual load profile — split, sized to the actual load rather than to the floor area
- New construction or a gut renovation of a multi-tenant building — VRF is increasingly the default, and the time to decide is at design, not after the ducts are in
ZK Mechanical designs, installs and services all three configurations across the GTA and Hamilton. See our commercial HVAC services for scope, or tell us about the building and we'll price the options side by side.
Frequently asked questions
What is a rooftop unit (RTU)?
A rooftop unit is a self-contained commercial HVAC system that combines the compressor, condenser, evaporator, gas heating section, and blower in a single cabinet installed on the roof. A single duct penetration connects it to the building below. RTUs are common in strip malls, retail boxes, warehouses, and single-tenant offices because they keep all equipment outside the leased space and simplify service access.
What is a split HVAC system?
A split HVAC system separates the outdoor components (compressor and condenser) from the indoor components (evaporator coil and air handler), connecting them with refrigerant lines. Split systems are common in multi-tenant offices, restaurants, hotels, and buildings where the roof can't support a heavy rooftop unit. They allow more flexible zoning and quieter outdoor unit placement.
Which is more expensive — RTU or split?
Like-for-like, RTUs typically cost slightly more installed than equivalent split systems — RTUs include integrated gas heat in a single cabinet and require crane lifting. A 10-ton RTU runs $22,000 to $35,000 installed; an equivalent 10-ton split system runs $18,000 to $32,000. VRF systems cost more upfront ($35,000 to $60,000 for a 10-ton 8-zone) but deliver multi-zone capability that simple RTUs cannot.
How long does a commercial RTU last?
Commercial rooftop units typically last 15 to 20 years with proper maintenance in the GTA. Units that skip annual maintenance often fail closer to 12 years. After 15 years, repair costs spiral and you're typically missing 30%+ efficiency gains from current equipment, making replacement the better long-term decision.
Can I convert from RTU to split system or vice versa?
Yes, but it's typically a major retrofit. Converting from RTU to split requires installing indoor air handlers, ground-mounting the condenser, running refrigerant lines, and either repurposing or removing the rooftop ducts. Converting split to RTU requires roof structural assessment, removing indoor equipment, and adding a curb. Most building owners stick with the original configuration unless a major building renovation is happening.