Cold climate heat pumps for commercial buildings

Air-source heat pumps have improved dramatically over the past two decades. Variable-speed compressors, vapour injection and better refrigerant circuits now let many models deliver useful heat well below -20°C (-4°F), and some continue operating below -25°C (-13°F). These "cold climate" heat pumps are a central technology for electrifying commercial heating in Canada.

They are not magic, though. Heating capacity and efficiency both fall as outdoor temperature drops, just when the building needs the most heat. Designing a commercial system that works in Edmonton or Winnipeg, not just in Vancouver, requires attention to capacity at design conditions, backup heat, defrost and controls.

What makes a heat pump "cold climate"

There is no single regulatory definition in Canada, but the term usually means a heat pump designed to maintain a high share of its rated capacity and a reasonable COP at low outdoor temperatures. Common features include:

• Variable-speed (inverter) compressors that can run faster at low temperatures to maintain capacity
• Vapour injection or enhanced vapour injection, which improves capacity and efficiency at high compression ratios
• Larger outdoor coils and optimized refrigerant circuits
• Smart defrost controls that defrost only when needed
• Base pan heaters and drainage that prevent ice build-up

In North America, the Northeast Energy Efficiency Partnerships (NEEP) cold climate air-source heat pump specification is widely used to identify qualifying products, mainly residential and light commercial. It sets minimum performance at -15°C (5°F), including a COP of at least 1.75 at maximum capacity, and requires reporting of performance at other low temperatures. Utility incentive programs in Canada often reference it or similar criteria.

How performance changes with temperature

The colder it is outside, the more work the compressor must do to lift heat to indoor temperatures. Typical trends for a cold climate unit look like this:

These are general ranges. Real values vary widely between products, so always use the manufacturer's extended performance tables, not nominal ratings. Even at a COP of 1.5, a heat pump still delivers 50 percent more heat per kilowatt-hour than electric resistance heating.

Design steps for commercial systems

1. Use the right design temperature. Take the January 2.5 percent or 1 percent design temperature for the location from the National Building Code climatic data or the applicable provincial code. Our guide on selecting outdoor design conditions explains the options.
2. Calculate the heating load at that temperature, including ventilation air. Ventilation is often the largest single heating load in commercial buildings in cold climates.
3. Check heat pump capacity at the design temperature, after derating for defrost and for piping length where applicable.
4. Decide the balance point strategy. Determine the outdoor temperature below which the heat pump alone cannot meet the load, and plan how supplementary heat will cover the rest.
5. Model annual performance. An hourly energy model using local weather shows how much of the annual heating energy the heat pump delivers and what the backup provides.
6. Check electrical capacity. Electrification can significantly increase peak electrical demand, especially if backup is electric resistance.

Backup and supplementary heat

Most commercial cold-climate heat pump systems in the colder parts of Canada include some form of supplementary heat.

Even when the heat pump can meet the design load on paper, consider redundancy. A building that relies on a single heat pump for all heat is vulnerable if that unit fails during a cold snap.

Defrost

When the outdoor coil operates below about 0°C (32°F) in humid conditions, frost forms on it and reduces airflow and capacity. Heat pumps defrost by temporarily reversing the cycle or by using hot gas bypass. During defrost, heating output to the building stops or drops, and in systems without backup the supply air may cool noticeably.

Design responses:

• Provide supplementary heat or a buffer tank (for air-to-water systems) to cover defrost periods
• Stagger defrost across multiple outdoor units
• Provide drainage for defrost water so it does not form ice under the unit
• Raise units on stands above expected snow depth and protect them from drifting

Applications in commercial buildings

Cold climate heat pumps appear in several forms:

• Ductless and ducted splits for small buildings and individual zones
• Variable refrigerant flow systems serving whole floors or buildings; see VRF systems explained
• Heat pump rooftop units, increasingly available with cold climate capability
• Air-to-water heat pumps feeding hydronic systems, covered in air-to-water heat pumps for commercial heating
• Heat pump dedicated outdoor air systems, which handle the large ventilation heating load

Controls

Good controls make the difference between a heat pump that does most of the heating and one that hands the job to backup heat.

• Lock out backup heat above a set outdoor temperature, so it does not run when the heat pump can cope.
• Use staged backup with time delays rather than switching on all backup at once.
• Avoid aggressive morning warm-up that forces backup heat; use optimal start with longer ramps.
• Trend outdoor temperature, heat pump capacity and backup heat operation to verify actual performance.

Frequently asked questions

Can a heat pump heat a commercial building in Edmonton or Winnipeg?

Yes, cold climate heat pumps can provide most of the annual heating energy in these climates, but they usually need supplementary heat for the coldest hours. The share covered depends on product selection, sizing and controls.

Are heat pumps cheaper to run than gas?

It depends on provincial electricity and gas prices, carbon pricing and the heat pump's seasonal COP. In some provinces heat pumps cost less to run; in others they cost more but reduce emissions. A life-cycle cost analysis with local rates is required.

How long do cold climate heat pumps last?

Service life is generally similar to other packaged heat pump equipment, often around 15 to 20 years with good maintenance. Harsh exposure and poor snow management can shorten it.

Key takeaways

• Cold climate heat pumps maintain useful capacity well below -20°C (-4°F), but capacity and COP fall as temperature drops.
• Select equipment using extended performance data at the local design temperature, not nominal ratings.
• Plan supplementary heat and redundancy, especially in Prairie and northern climates.
• Design for defrost, snow and drainage around outdoor units.
• Use controls that keep the heat pump as the primary heat source, and verify performance with trend data; high-efficiency HVAC design can help balance capital, operating cost and carbon.