Furnace and heat pump sizing in Nunavut
Iqaluit runs about 9,642 heating degree-days a year, which puts it in the very cold band at roughly 60 BTU per square foot of heating. It is the only station in the territory with a published annual degree-day normal.
Nunavut has the most severe heating climate in Canada by a wide margin. Rule-of-thumb sizing has no useful meaning at these degree-day totals: heating design here is an engineering exercise, and this page exists to show the scale of the difference, not to substitute for one.
Heating degree-days and January temperatures in Nunavut
Degree-days below 18 °C and January temperatures from the Environment and Climate Change Canada Canadian Climate Normals 1991–2020. The band column applies the mapping described on the Canada index.
| City | Heating degree-days (18 °C) | January daily mean | January daily min | Band | BTU/sq ft |
|---|---|---|---|---|---|
| Iqaluit | 9,642 | -26.0 °C | -29.9 °C | Very cold | ~60 |
Worked example
Take a 1,500 sq ft home in Iqaluit. At the very cold band of 60 BTU per square foot:
1,500 sq ft × 60 BTU/sq ft = 90,000 BTU/h
A gas furnace is rated by input, so divide the output by the AFUE to get the rating you shop for: at 95% AFUE that is about 95,000 BTU/h of input. That falls between the standard 80,000 and 100,000 BTU/h sizes. Which one you should buy is exactly the question a load calculation answers and a rule of thumb cannot — rounding down leaves the house short on the coldest nights, and rounding up brings the short-cycling problems of an oversized furnace. Run your own numbers in the furnace-size calculator, and use AFUE typical bands if you do not have the nameplate.
At these degree-days the arithmetic above is an illustration of scale, not a usable size. Envelope performance dominates the load long before equipment selection does.
Heat pumps in Nunavut
A heat pump loses capacity as the outdoor temperature falls, exactly when the house needs the most heat. The temperature where its output equals the house load is the balance point; below that, backup heat makes up the difference. Iqaluit averages a January daily minimum around -29.9 °C, and the design condition is colder still.
At these degree-days a heat pump needs a genuine cold-climate rating and backup heat sized to carry the house on its own at the design condition, not merely to supplement. Rated capacity at 8.3 °C tells you almost nothing about performance here; ask for the capacity table at low outdoor temperature.
The heat-pump-size calculator works from the same band, the balance-point calculator finds the crossover temperature. Dual fuel and the balance point explains where backup heat takes over.
A note on units
Canadian homes are almost always described in square feet and equipment is rated in BTU/h or tons, but outdoor temperature is in °C and degree-days are on the 18 °C basis rather than the American 65 °F. The two degree-day scales are not interchangeable: an American HDD65 figure is about 1.8× the Canadian HDD18 number for the same place. Every degree-day figure on this page is the Canadian 18 °C basis. If you have a floor area in square metres, multiply by 10.76 to get square feet before using the calculators.