What an F280 Heat Loss Calculation Actually Tells You About Your Heat Pump

Last updated April 2026

An F280 is the room-by-room heat loss calculation that determines what size heat pump your home actually needs. Skip it — go with rule-of-thumb sizing, the BTUs-per-square-foot eyeball, the contractor who quotes from a driveway look — and you end up in one of two failure modes. Either an oversized unit that short-cycles and bleeds 15–30% of its seasonal efficiency, or an undersized unit that runs electric resistance backup all winter and quietly torches the savings story the rebate was supposed to fund. Both fail. Both are common. The F280 is the document that prevents both.

If you've started shopping for a Kootenay heat pump, you've probably seen "F280 required" on a contractor's quote sheet or a rebate checklist without an explanation of what it is or why it matters. This is that explanation.

What an F280 actually is

CSA F280-12 is the Canadian Standards Association's national standard for residential heating and cooling load calculation. The full title is Determining the Required Capacity of Residential Space Heating and Cooling Appliances. Every HPCN-registered contractor doing rebate-eligible work in BC follows this standard for sizing.

The calculation takes inputs about your specific home and outputs a single number that matters: the peak heat loss at design temperature, expressed in BTU/hr.

Inputs include:

• Insulation R-values for ceiling, walls, basement, slab, rim joists
• Window and door areas, U-values, and orientations
• Air infiltration rate (ideally measured with a blower door)
• Climate zone and outdoor design temperature
• Indoor design temperature, usually 21°C
• Internal gains from people, lights, appliances
• Foundation type and basement conditions

Output: how many BTU/hr your home loses on the coldest design day. That number, plus a small safety margin, sets the size of the heat pump.

Why this matters in cold-climate sizing

Nelson's outdoor design temperature sits between -20°C and -25°C. Castlegar and Trail are similar; the Slocan Valley and Kaslo run a couple of degrees colder.

At those temperatures, sizing errors get expensive in a hurry.

Undersized heat pump. The unit can't keep up at design temp, so the controller calls for auxiliary electric resistance heat. Resistance heat runs at COP 1.0 — exactly as efficient as your old baseboards. If aux runs every cold morning all winter, you've turned a $1,800-a-year savings story into a $400-a-year savings story, and the homeowner's bill comes in higher than expected. They blame the heat pump. They blame the rebate. They tell their neighbour the technology doesn't work.

Oversized heat pump. The unit cycles on, hits setpoint in seven minutes, cycles off, repeats. Short-cycling kills inverter efficiency (most of the COP gains from a modern heat pump come from steady-state operation), accelerates compressor wear, and produces uneven temperatures because the airflow never establishes. Field studies put seasonal efficiency loss in the 15–30% range for chronically oversized installs.

The right size at design temp is a properly sized cold-climate unit running near its rated capacity for hours at a time when it's -20°C outside. That's where the math works.

Who can do an F280

Three roles legitimately produce F280 calculations:

A Certified Energy Advisor (CEA) registered with NRCan. CEAs do EnerGuide evaluations and produce F280s as standalone deliverables. This is the most common standalone F280 path, and the calculation feeds directly into the EnerGuide pre-retrofit baseline that HomeSave Central Kootenays requires anyway.

A licensed HVAC engineer or designer with appropriate software (Wrightsoft Right-Suite Universal, Hot 2000, CoolCalc, BetterBuiltNW). Used on larger projects or commercial work.

A trained HVAC contractor with the right software and competency. The HPCN credential pathway includes HRAI's residential heat loss methodology training, so HPCN-registered contractors are the practical default for residential heat pump projects.

Not every installer does F280s in-house. Some sub the work out to a CEA partner. Some do simplified calcs in spreadsheets. Some skip the calc and use rule-of-thumb sizing — which is the failure mode the standard exists to prevent.

When a contractor's quote includes an F280 line item, that's a good sign. When it doesn't, ask.

What good vs. bad F280 looks like

Bad F280, version one. The "30 to 40 BTU per square foot" rule of thumb. A 2,000 sq ft Nelson heritage home gets sized at 60,000–80,000 BTU/hr regardless of insulation, windows, or air leakage. This will be wrong in either direction — and is consistently wrong on the high side, producing oversized installs.

Bad F280, version two. A real calculation done with assumed default values for insulation and infiltration that nobody measured. R-12 walls assumed in a knob-and-tube heritage home that's actually R-0 in the cavities. Windows assumed at U-2.0 when they're single-pane wood sash at U-5.5. The calculation looks rigorous but the inputs are fiction, and the output is wrong.

Good F280. Room by room. Measured insulation values where accessible, professional estimates where not. Actual window U-values from labels or manufacturer specs, not defaults. Blower door measurement of infiltration if available; documented assumption if not. Climate zone and design temperature appropriate to the actual location, not provincial averages. The output report shows the heat loss for each room, which lets a multi-zone ductless installer size each indoor head correctly rather than guessing at zone allocation.

A homeowner doesn't need to read every line of an F280 report. But it should exist as a document, with a date, with the home's address on it, with room-by-room numbers.

Common Kootenay F280 surprises

Older Nelson homes — the ones in Fairview, Uphill, and Rosemont built before WWII — often come in surprisingly high on the first calculation. Knob-and-tube wiring in uninsulated wall cavities, single-pane windows, drafty rim joists, and unsealed basements can push heat loss to 40+ BTU/sq ft. A 1,600 sq ft home that "should" need a 36,000 BTU/hr heat pump might actually need 60,000 BTU/hr in its current state.

This is where a lot of Kootenay projects make a smart pivot. Adding wall insulation, sealing the rim joist, and replacing the worst windows can drop the heat loss number to 25–30 BTU/sq ft, which moves the home into a smaller heat pump size class. Smaller equipment costs less, and a smaller unit running near capacity at design temp performs better than a larger unit short-cycling at part load.

The F280 done before insulation work and the F280 done after are sometimes two different heat pump conversations. Worth knowing before equipment gets ordered. (Insulation retrofit options for older Nelson homes covers the envelope upgrade side.)

The F280-rebate connection

CleanBC ESP and HRR rebate applications require sizing documentation. In practice this means an F280 (or equivalent calculation method recognized by CSA F280-12) attached to the contractor's submission. Without it, the rebate isn't processed.

There's a quieter consequence too. Even if a poorly executed F280 satisfies the paperwork requirement, it doesn't protect you from the install going sideways. The rebate gets paid; the wrong-sized heat pump gets installed; the homeowner's actual energy bills come in higher than promised. The rebate program doesn't refund you for that.

This is why the F280 is contractor-side work but homeowner-side risk. The contractor produces it; the homeowner lives with the equipment it specified.

What to ask the contractor

Four questions worth asking before signing a quote:

• "Do you do F280s in-house, or do you partner with a Certified Energy Advisor?"
• "Can I see an example F280 report from a similar home?"
• "What software do you use — Wrightsoft, Hot 2000, something else?"
• "Will the report show room-by-room heat loss, or just a whole-home number?"

The answers tell you whether you're dealing with a contractor who treats sizing as a discipline or as a checkbox. (How to vet a rebate-approved heat pump installer goes deeper on the credential side.)

What an F280 costs

Bundled into the contractor's installation quote in most cases. You don't see a separate line item; the work is part of design.

A standalone F280 from a Certified Energy Advisor — useful if you want an independent sizing check before accepting a contractor's quote, or if you're shopping multiple contractors and want a neutral document — typically runs $300–$500 in the Kootenay market. A full EnerGuide pre-retrofit evaluation, which includes the F280 plus a blower door test and a HOT2000 model used by HomeSave for the performance baseline, runs $400–$600 and is partially rebatable through several programs.

If you're pursuing HomeSave Central Kootenays anyway, the EnerGuide evaluation produces both the rebate baseline and the F280 in a single visit.

FAQ

Do I really need an F280, or can I just go with what the contractor recommends?

You need one for the rebate. You need one for the equipment to work properly. The two requirements collapse into the same document. A contractor recommending a size without producing an F280 is either doing the calculation and not showing you, or skipping it — neither is acceptable on a rebate-eligible project.

Can I get an F280 done before I pick a contractor?

Yes. A Certified Energy Advisor can produce one as a standalone deliverable for $300–$500. This gives you a neutral document to compare contractor quotes against. Useful if quotes come back varying widely on equipment size, which they sometimes do.

How long is an F280 valid?

For a stable home, indefinitely — the heat loss doesn't change unless the building does. If you renovate, add insulation, replace windows, or finish a basement between the calculation and the install, the F280 should be re-run. Most contractor F280s are produced within weeks of the install and don't run into staleness issues.

What software is acceptable?

Wrightsoft Right-Suite Universal is the industry standard for HVAC contractors. Hot 2000 (NRCan's residential energy modeling tool) is what most CEAs use and produces both EnerGuide and F280 outputs. Several other CSA-compliant tools exist. The standard matters more than the software brand — ask whether the calculation conforms to CSA F280-12.

My contractor said he uses "Manual J" instead. Is that the same?

ACCA Manual J is the American equivalent of CSA F280. Similar methodology, slightly different defaults and climate data tables. For a BC project, F280 is the standard the rebate programs expect, and CSA F280-12 references some Canadian-specific climate and infiltration assumptions that Manual J doesn't. Acceptable in practice but ask the contractor to produce F280-format output for the rebate file.

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How Kootenay Energy fits in

We're a concierge service that matches Kootenay homeowners to HPCN-registered heat pump installers and walks the rebate paperwork through to payout. The F280 itself is contractor-side work — the installer or their CEA partner produces the calculation. What we do is make sure the contractor on your project does it properly, that the report is filed correctly with your rebate application, and that the size class on the equipment matches what the F280 actually called for. Two minutes of running the rebate calculator tells you what your stack looks like; from there we handle the matching, the documentation, and the deadlines.

Cold-climate equipment selection is a separate conversation we cover in Heat pumps in Kootenay winters. The full pillar lives at Heat pumps in the Kootenays.

External references: CSA F280-12 standard, NRCan EnerGuide for Homes, HRAI residential training.