Compliance. Methodology comparison only. Not CSA certified, not ACCA approved/certified, and not a substitute for stamped design where required. Follow the authority having jurisdiction.

Same physics, different rulebook

ACCA Manual J (commonly 8th Edition in US field software) is the US industry method for residential peak heating and cooling loads. It pairs with ASHRAE-style climate data and ZIP-mapped design temperatures in many apps.

CSA F280-12 is Canada’s determining the required capacity of residential space heating and cooling appliances standard. Canadian programs, builders, and inspectors often expect F280-based heat loss/gain with Canadian design temperatures — frequently referenced via NRCan / recognized climate datasets keyed by postal code or location.

Both start from envelope UA, windows, infiltration, internal gains, and design weather. They are not drop-in interchangeable worksheets.

One set of physics, two rulebooks Both methods start from the same physics: envelope UA, windows, infiltration, internal gains and design weather. ACCA Manual J 8th Edition applies it in the United States with ASHRAE and ENERGY STAR design temperatures by ZIP, pairs with Manual S, and reports in Btuh. CSA F280-12 applies it in Canada with Canadian design temperatures by postal code, produces the report Canadian authorities expect, and works in English, French and SI units. Shared physics envelope UA · windows · infiltration internal gains · design weather ACCA Manual J 8th Ed. United States ASHRAE / ENERGY STAR temps by ZIP Pairs with Manual S for equipment Imperial first, reported in Btuh CSA F280-12 Canada Canadian temps by postal code The report AHJs and programs expect EN / FR, SI friendly
The physics is not in dispute. What differs is the climate data you are required to use, the deliverable, and who has to accept it.

What usually changes in practice

Topic Manual J (typical US field use) CSA F280-12 (typical CA field use)
Climate data ASHRAE / Energy Star county & ZIP mapping, MJ8 daily range Canadian design temps (e.g. NRCan postal / location tables)
Governing document ACCA Manual J (+ Manual S for equipment) CSA F280-12 (+ local code / utility rules)
Basements / below grade MJ procedures for basement walls, slabs, crawlspaces F280 treatments and Canadian construction defaults — verify against the edition and software you use
Ventilation / HRV Manual J ventilation and infiltration models F280 + often tighter tie-in to Canadian ventilation practice
Deliverable MJ load + often Manual S sizing sheet F280 heat loss/gain report expected by many AHJs / programs
Language / market US English, imperial-first tools common EN/FR markets; SI-friendly tools matter

Climate data is not a rounding error

Design dry-bulb (and the coincident moisture story for cooling) drives load more than most envelope nitpicks. Pulling a Buffalo ZIP for a Niagara postal code, or hand-waving “close enough,” can move furnace and heat-pump selection across size bins.

Use the climate source your method and AHJ recognize. Canadian postal-code tables and US ZIP tables are curated differently — do not assume one app’s US database covers a Canadian permit.

Basements and cold-climate envelope

Canadian housing stock puts more load story into basements, slabs, and below-grade walls than many US sunbelt replacements. F280 workflows and Canadian default assemblies reflect that. If you only ever ran MJ8 on crawlspace ranchers, re-check how your F280 tool wants foundation walls, insulation planes, and conditioned vs unconditioned basements entered.

Ventilation and airtightness

Tighter envelopes and HRV/ERV systems change both infiltration credit and deliberate ventilation load. Enter the mechanical ventilation you will actually leave running at design — not the leaky-house folklore from a decade ago. Mis-entered ventilation is a common reason two “good” calcs disagree on the same address.

Reporting scope and AHJ expectations

  • Ask early: does the permit, builder, or utility want F280, Manual J, or a named software report?
  • Room-by-room vs block still matters for ducts — see block load vs room-by-room — but the standard name on the cover sheet must match the request.
  • Equipment selection may still reference OEM expanded data and local oversize rules; F280 gives the load, not a free pass on Manual S / manufacturer limits.

Do not “convert” a Manual J tonnage into F280 by multiplying by a fudge factor. Re-run with the correct climate table and method.

Which app should you use?

Neither app is CSA certified or ACCA approved. Both are professional estimating aids for qualified technicians.

FAQ

Is CSA F280 the same as Manual J?

No. Related building-physics goals, different standards, climate sources, and typical deliverables.

Which method should I use in Canada?

Whatever the AHJ, builder, or program specifies — often CSA F280-12. Confirm before you spend the site survey.

Can I convert Manual J to F280?

Not by scaling. Re-enter the job in F280 with Canadian design temperatures.