Commercial VRF system: what a Montréal building demands

Two bids on the same desk, for the same three-storey building going through a fit-out. The first swaps the aging rooftop units for equivalent ones. The second proposes a commercial VRF system: one machine on the roof, some thirty indoor units, every room on its own setpoint. The price gap is significant, and so is the gap in what is being promised. Yet the question that will actually decide this project is neither price nor comfort, and neither bid raises it: how much refrigerant is this building about to circulate inside its walls, and who answers for it to the Régie du bâtiment?

What a commercial VRF system actually is

A VRF system — variable refrigerant flow — connects one or more outdoor units to many indoor units through a refrigerant piping network. A variable-speed compressor continuously modulates the refrigerant sent to each zone, so every room can heat or cool independently of its neighbours.

Two architectures exist, and the difference matters at signing time. In heat-pump configuration, every indoor unit on a given loop does the same thing at the same time: all heating, or all cooling. In heat-recovery configuration, a branch controller lets opposing zones run in opposite modes at once — heat pulled out of an overheated room is moved to a room that needs it instead of being dumped outside. That second architecture is what justifies the technology in most commercial buildings, and it is also the one whose piping and controls cost the most.

Where a commercial VRF system genuinely wins in Montréal

VRF is not a generically better way to condition a building: it answers a specific building type. Three profiles come up again and again across Greater Montréal.

Buildings cut into small zones with opposing exposures. Offices, clinics, language schools, hotels — a floor whose south façade takes the March sun while the north side stays in shade is exactly where heat recovery earns its keep. In our climate the shoulder seasons are long, and those April weeks of heating overnight and cooling by mid-afternoon are where the system pays back its premium.

Retrofits with nowhere to run ductwork. Montréal’s commercial stock includes a lot of brick buildings with low ceilings, wood floors and service shafts already crowded with risers. Threading a main duct network through them sometimes costs more than the equipment. A refrigerant line a few centimetres across goes where a duct will not.

Buildings taking combustion out of the envelope. A VRF is a heat pump: no burner, no chimney, no gas train inside the building. For an owner watching municipal rules tighten around combustion heating in new construction, that is a structural argument — provided someone has already checked what happens to heating capacity in January.

Three families to compare before you sign

The useful way to read this table is not “which one wins” but “where does the constraint move”. VRF removes ducts and shafts, and adds refrigerant in occupied space, a dependency on proprietary controls, and a ventilation load handled somewhere else. The water-versus-air distribution question is worked through in our piece on choosing between hydronic and forced-air systems; VRF simply adds a third family, with its own list of obligations.

Will a commercial VRF system still heat at −25 °C?

Yes — but not at the same output, and that is the whole nuance. Trane’s white paper on applying VRF in cold climates is explicit that modern systems far exceed conventional heat pumps at low outdoor temperatures, down to roughly −35 °C. The same document insists on the heating derates a designer has to account for: available heating capacity falls as outdoor air cools, and every defrost cycle briefly takes output away from the building.

Trane describes several ways to absorb that loss: oversizing indoor and outdoor units for heat, upsizing the dedicated outdoor air system so it carries part of the heating load, locating condensers indoors, or moving to water-source VRF — which, per the paper, delivers greater efficiency and less derating.

Translated into Montréal practice: the question to put to a bidder is never “how cold can your system run?”. It is “how much heating capacity remains at this building’s design temperature, and what carries the load below it?”. A numeric answer always exists in the manufacturer’s tables. Its absence from a bid says a great deal.

Refrigerant is now a regulated object

This is what VRF projects discover too late. The CSA B52 mechanical refrigeration code applies in Québec through the Pressure Vessels Regulation, and its 2023 edition has been in force since February 1, 2025. Among other things, that code governs how much refrigerant is permitted per occupied space: the smaller the room being served, the lower the charge tolerated in it. A system carrying a large total charge across three floors therefore has to be checked room by room rather than in aggregate — one small closed office at the end of a branch can trigger a mitigation measure on its own.

On top of that comes the shift to A2L refrigerants, mildly flammable, now standard on recent product lines. In November 2024 the Régie du bâtiment issued a directive allowing these refrigerants to be treated as A1 when calculating the installation class and the supervision mode set out in the Stationary Enginemen Regulation — under precise conditions, including compliance with the maintenance requirements of clause 8.4.2 of CSA B52 and verification of permanent leak detectors at intervals never exceeding one year. In other words: the regulatory flexibility is real, and it is paid for in documented maintenance.

Finally, Québec’s Halocarbons Regulation targets the owner of the equipment, not the contractor who installed it. Reporting releases, periodic leak testing above a capacity threshold, using certified technicians — those duties arrive with the system and stay in the building file for twenty years. A serious commercial air conditioning provider folds them into the maintenance agreement at commissioning rather than discovering them at the first inspection.

Field case: Laval, two office floors and one room that blocked everything

An office building in Laval, two floors converted into clinics and professional offices. The selected design: heat-recovery VRF, thirty-two indoor units, ventilation air from a dedicated rooftop unit. We were brought in for a design review before the equipment order went out.

The design held up, with one exception. A closed four-square-metre records room, with no transfer grille, was served by an indoor unit on the same loop as the rest of the floor. Applying the code’s per-occupied-space charge logic, that one small room imposed a constraint the far larger open floor would never have triggered. The related second finding: the outdoor air unit had been sized strictly for ventilation, with no heating reserve — so nothing was standing by to support the VRF through January defrost cycles.

Corrections, made before the order and without major cost: the records-room unit was dropped from the scope, the room instead picking up air through a transfer grille from the corridor, and the outdoor air unit was moved up one step in heating capacity. A system built exactly as originally designed would have sailed through commissioning — and stalled at the first regulatory inspection, that time with the walls closed up.

What to demand from a VRF bid

Before comparing two prices, ask for four documents in writing. One: heating capacity at the building’s design temperature, not just the minimum operating temperature. Two: the refrigerant charge calculation per occupied space, room by room, for the worst room rather than the average. Three: a description of the ventilation system, its heating capacity and how it handles ventilation and air quality. Four: the list of maintenance and verification duties that transfer to the owner at handover, with their frequency.

A bid that supplies those four pieces will likely cost more than one that does not. That is as it should be: it did the work. Hydro-Québec incentives for commercial buildings can absorb part of the gap, and the rest comes back over the first year of operating a properly sized system. At Montréal Combustion this design review happens before equipment is ordered — the only point in a project where fixing a four-square-metre room still costs nothing.