Every heating system in Ontario should be sized from a heat loss calculation — the Building Code requires the full CSA F280 version for permits, and getting it wrong is how furnaces end up 3× oversized and heat pumps end up undersized. This free estimator uses the same physics as the stamped reports: transmission through every assembly, infiltration by construction era, ventilation, and your municipality’s actual SB-1 design temperature. We calibrated it against real stamped F280 reports from Ontario projects — it lands within roughly ±15% of the certified number for typical houses.
What it can’t do: room-by-room loads, per-room airflow, or carry a BCIN stamp — the things your building permit requires. For that, the certified CSA F280 report is $395 and takes 48 hours.
A CSA F280 sums four heat-loss paths at design conditions: conduction through every assembly (Area × ΔT ÷ effective R), below-grade losses, infiltration (the biggest lever — driven by construction-era airtightness), and ventilation. This estimator runs the same energy balance with era-typical assemblies instead of your exact drawings, at your municipality’s real SB-1 January 2.5% design temperature.
We tested the engine against real BCIN-stamped F280 packages from Ontario projects — different designers, different towns, 2019 through 2026. It landed within ±15% of the certified number on every one, and it copies what real stamping practice does: construction-class airtightness defaults, full ventilation load, and a hydronic piping allowance on radiant systems.
No room-by-room loads, no per-room airflow targets, no blower-door input, no BCIN stamp — the four things your permit application requires. Use the estimate to sanity-check quotes and shortlist equipment; use the certified F280 to submit.
Because most Ontario furnaces were sized by the 50–60 BTU per square foot rule of thumb, which oversizes modern and renovated homes by 2–3×. A 2,000 sq ft house built to today’s OBC 2024 requirements in Barrie calculates around 30,000–40,000 BTU/h — not the 100,000 the rule suggests. See what oversizing actually costs you.
No. Ontario building departments require a certified CSA F280 calculation — room-by-room, at your municipality’s design temperature, BCIN-stamped with a signed Schedule 1. This tool tells you what to expect; the stamped report is what you submit. $395, 48 hours, accepted province-wide.
The Ontario Building Code’s Supplementary Standard SB-1 January 2.5% values — the same ones stamped reports use. Toronto −18°C, Barrie −24°C, Orillia −25°C, Muskoka −26°C, Windsor −16°C. The wrong value is one of the most common reasons permits get rejected.
The design heat loss is exactly the number a cold-climate heat pump must meet at your design temperature — using the manufacturer’s output at that temperature, not the nameplate. For the certified version with equipment verification, see heat pump sizing.
Like the number? Make it official. The certified room-by-room CSA F280 — BCIN-stamped, permit-ready — from $395 in 48 hours.
Get Free Quote →Upload your floor plans and tell us your municipality. Your designer of record runs the full room-by-room calculation from your actual drawings — real assemblies, real glazing, per-room airflow targets — and delivers the BCIN-stamped report your building department requires. Mention your estimate from this calculator and we’ll tell you how close it landed.