Refrigerant selection is the most consequential systems decision in a cold storage project. It sets capital cost, energy cost, machinery room design, regulatory burden, staffing requirements, and how exposed you are to the next phase-down. It is also frequently decided by default: whatever the last project used.
The three options at a glance
| Ammonia (NH₃) | CO₂ transcritical | Synthetic (HFC/HFO) | |
|---|---|---|---|
| Efficiency at low temp | Excellent | Very good | Moderate |
| Capital cost | Moderate | Higher | Lowest |
| Global warming potential | Zero | Negligible | Moderate to high |
| Phase-down exposure | None | None | Significant |
| Toxicity | Toxic | Asphyxiant at concentration | Low |
| Operating pressure | Moderate | Very high | Moderate |
| Operator expertise | Specialised, certified | Specialised | Widely available |
| Best suited to | Large single-site facilities | New builds, mid to large | Small loads, tight budgets |
Ammonia
The long-standing default for large industrial refrigeration, and for good reason: it is thermodynamically excellent at freezer temperatures, it has zero global warming potential, and it is inexpensive per kilogram. At scale, nothing beats it on operating cost.
The costs are on the other side of the ledger. Ammonia is toxic, which drives machinery room design, detection and ventilation, emergency planning, and the qualifications of the people who operate it. Above the federal reporting threshold, a facility falls into a formal environmental emergency planning regime with its own obligations. Some municipalities and some insurers apply additional constraints, and a few urban sites are effectively closed to it.
Ammonia charge size is a design variable, not a fixed output. Low-charge packaged and central systems have brought typical charges down substantially, which can move a facility below a regulatory threshold entirely. If ammonia is right on efficiency but awkward on compliance, this is the first thing to model.
CO₂ transcritical
The direction of travel for new builds, particularly where ammonia is difficult and synthetic refrigerants are unattractive. CO₂ is non-toxic, non-flammable, and has negligible global warming potential, so it sidesteps both the safety burden of ammonia and the phase-down exposure of HFCs.
The trade-offs are real. Operating pressures are far higher, which means more expensive components and pipework and a smaller pool of contractors genuinely competent to install it. Efficiency historically fell away in hot ambient conditions, though parallel compression and ejector technology have largely addressed that, and Canadian climates are favourable to begin with.
Where a project needs a system that will still be compliant and serviceable in twenty years, this is usually the strongest answer.
Synthetic refrigerants
HFCs are the low-capital option and the systems are simple to install and service, with contractors available everywhere. For small loads, single-zone coolers, and tight budgets, they remain a defensible choice.
For a large facility with a twenty-year horizon they are increasingly hard to justify. Canada is progressively phasing down HFC supply, which pushes refrigerant prices up over the asset’s life, a cost that lands squarely on whoever owns the building at the time. Lower-GWP HFO blends improve the environmental position but do not remove the exposure.
How to actually decide
Work through these in order. The answer usually becomes obvious two or three questions in.
- How large is the load, and how cold? Large and deep-frozen pushes hard toward ammonia or CO₂. Small and chilled leaves everything open.
- What does the site permit? Urban, close to residential, or constrained on setbacks makes ammonia harder and sometimes impossible.
- Who will operate it? An ammonia plant needs qualified operators available. In some regions that is a genuine constraint on the decision.
- What is the holding period? A long hold makes energy and refrigerant price exposure dominate. A short hold weights capital cost more heavily, though a buyer will price the system you installed.
- What do your tenants or customers require? Institutional tenants increasingly have ESG reporting obligations that make natural refrigerants a leasing advantage.
The cost picture
Refrigeration plant commonly represents a substantial share of total cold storage construction cost, enough that the system decision moves the project budget materially, and enough that an aging plant in an existing building is a major valuation factor. Precise ranges depend on load, temperature, configuration, and market conditions at the time of procurement, which is why we develop them per project rather than publishing a single number.
What we will say generally: the cheapest system to install is rarely the cheapest system to own, and the gap compounds over a twenty-year hold.
This guide is general orientation. Refrigerant selection and system design require a refrigeration engineer of record working from your actual load calculation. We bring one in on every project and would encourage the same on yours.