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How to size a heat pump - CSA F280 explained

By the Vancouver Heat Pump Pro team

Updated

The most common heat pump mistake we see isn't the brand - it's the size. And the most common way it happens is someone looking at the old furnace's label and matching it.

Why the old furnace's size is the wrong starting point

Many gas furnaces in Metro Vancouver homes are oversized, sometimes by a lot. Gas furnaces were cheap to oversize and an oversized furnace mostly just cycles more. Heat pumps are different: oversizing costs real money up front and hurts comfort.

Homes also change. New windows, added insulation, or a sealed attic can cut heat loss significantly since the furnace went in.

What a CSA F280 heat load calculation does

CSA F280-12 is the Canadian method for calculating heating and cooling loads. A proper calculation looks at:

  • Each room's walls, windows, ceilings and floors and their insulation values
  • Window size, type and orientation
  • Air leakage, estimated or measured with a blower door test
  • Local design temperatures for heating and cooling
  • Ventilation and internal gains

The result is the heat the house needs at the design condition, room by room - which also tells us how to split zones on a multi-split system.

What BC's rebate rules require

For the BC standard rebate, a whole-home heat pump must be sized to keep the home at 22°C at an outdoor temperature of −5°C or colder without electric resistance heat, and it must heat 80% or more of the home's conditioned space. The calculation must be done with CSA F280-12 verified software. See the rebate guide for the full rules.

−5°C is a sensible design point for most of Metro Vancouver. Higher neighbourhoods, like Westwood Plateau or Burke Mountain in Coquitlam, run colder and deserve a closer look.

Questions to ask any installer

  1. Will you do a room-by-room CSA F280 calculation, and can I have a copy?
  2. What design temperature are you using?
  3. What's the heat pump's output at that temperature - not just its nominal size?
  4. How will backup heat be controlled so it doesn't run when it isn't needed?

Get a proper heat load calculation

Every quote we write starts with a room-by-room CSA F280 calculation, and you get a copy.

Get my free quoteor call (604) 332-3083

Quick answers

It's the Canadian standard method for calculating how much heat a house loses (and gains in summer), room by room, based on its walls, windows, insulation, air leakage and local design temperatures. BC rebate programs require it.

Not reliably. Two 2,000 square foot homes can have very different heat loss depending on insulation, windows and air tightness. Square-foot rules usually oversize.

It short cycles, dehumidifies poorly in summer, costs more to buy and wears faster. Variable-speed units tolerate some oversizing, but not much.

Call(604) 332-3083Free quote