CSA F280 Heat Loss Calculation for Your Ontario Building Permit

What your building department is actually asking for

The wording varies. The City of Barrie's new dwelling checklist, for example, asks for heat loss and heat gain calculations, a formula sheet, a thermal load calculator and an air leakage calculator, and states that they "must meet HRAI-CSA F280-12 or ASHRAE design standards." Other municipalities ask for "heat loss" or "HVAC design" and mean something similar.

If the letter you received names a document you have never heard of, send it to us and we will tell you what it is.

What we need from you

Four things, and most people already have three of them:

If you don't have the assemblies, say so. We will use the current code minimums for your climate zone and flag every one of them on the assumptions page, so your reviewer can see exactly what was assumed and correct it if your build differs.

What you get

For the full mechanical package, nineteen pages that cover everything the HVAC designer signs: a submission checklist, room-by-room heating and cooling loads with design airflows, the surface-by-surface worksheets, the equipment and ventilation schedule, HVAC floor plans with the duct layout drawn on each level, the duct system summary and branch detail, the ventilation design data for OBC 9.32, the Energy Efficiency Design Summary data, an assumptions page listing anything assumed rather than read, and the review-and-seal page. The $395 heat loss and heat gain is the first half of that set.

The checklist page also names what the permit needs from others — the architectural drawings, a lot grading plan where the municipality wants one, an energy model if the house cannot meet the prescriptive package — so nothing arrives as a surprise after you apply.

See the complete sample package — all 19 pages →

That sample is a worked example — a code-minimum two-storey in Barrie, not a real client's house. It shows you exactly what arrives.

Why the number matters more than people expect

The sample house above, 3,020 ft² built to current SB-12 minimums in Barrie, loses 30,472 Btu/h at the design temperature. A contractor sizing it by square footage would commonly land on a 100,000 Btu/h furnace. That's roughly three times what the house needs.

An oversized furnace short-cycles, heats unevenly, wears faster and costs more to buy. This is the single commonest expensive mistake in Ontario residential heating, and the calculation is what prevents it.

Who can sign it

Two routes, and most people are only told about the first.

You hire a qualified designer. They complete the Schedule 1 Designer Information Form with their BCIN and take responsibility for the design. That is what we do for you.

You are the owner, building on your own lot. Ontario Building Code Division C, Article 3.2.5.1.(3)(b)(i) exempts an owner who designs a house they own from the designer qualification requirements. You can submit the documents yourself. The calculations still have to be right — the exemption is about who may design, not about the standard the work has to meet.

Tell us which you are and we will tell you what you need before you pay.

What it costs

Forty-eight hours from complete plans and payment. If your building department asks for a correction to something we got wrong, we fix it and reissue at no charge while your application is open.

Common questions

Is a heat loss calculation required by the Ontario Building Code? The Code requires heating equipment capacity to be based on the calculated design heat loss (Article 9.33.5.1), and references CSA F280 for how that calculation is done. Whether a particular permit application needs the document in the file is set by your municipality's submission requirements, which is why those vary.

Can I do it myself? If you own the lot and are designing your own house, yes — see the exemption above. Online estimators are not the same thing; they give a whole-house number with no room-by-room breakdown and no assumptions page, which is what a reviewer reads first.

My HVAC contractor says he'll size it. He may be right about the equipment. The building department still needs the document, meeting F280-12, with a Schedule 1 behind it.

The department has already asked for it and I'm holding up my build. That's the most common reason people call. The 48-hour turnaround exists for exactly that.

Does an ICF or high-performance house need a different calculation? Same procedure, different inputs. The result usually comes out substantially lower, and more of the difference comes from air sealing than from the wall's R-value. We run that comparison on every job.

How accurate is it? Our engine is checked against stamped packages produced by independent Ontario designers. On the most recent one it reproduced the structural load to within 0.0% and every component to within 0.4%. We publish the verification status of our software on every page we produce, including the fact that it has not completed the CSA F280-12 Clause 8 software verification — nobody should take a conformity claim on trust, including ours.

Start

Send your plans — we'll tell you what you need before you pay →

Adding a basement apartment, garage suite or ADU to a house you already own? That is a different job — no drawings, an existing furnace, and the question of whether it can carry both units. Start here instead →

Don't have plans in hand yet? Tell us about the project and we'll tell you what the permit will ask for.