Heat Loss Calculator Ontario 2026
Ontario Heat Loss Calculator — CSA F280-12
Calculate residential heat loss room-by-room using the official HRAI methodology required for Ontario building permits. Determine correct furnace sizing and meet Section 9.33.2.2 compliance.
📋 Project Information
🌡️ Design Conditions (Section A)
| Room Name | Level | Wall Area (sq ft) | Wall R-Value | Window Area (sq ft) | Window R-Value | Ceiling Area (sq ft) | Ceiling R-Value | Heat Loss (BTU/h) |
|---|
Level Factors & Distribution
| Level | Level Factor | Conductive Heat Loss (BTU/h) | Air Leakage Multiplier |
|---|---|---|---|
| Level 1 — Basement | 0 | 0.0000 | |
| Level 2 — Main Floor | 0 | 0.0000 | |
| Level 3 — Upper Floor | 0 | 0.0000 |
| Room | Level | Conductive (BTU/h) | Air Leakage (BTU/h) | Ventilation (BTU/h) | Room Total (BTU/h) |
|---|
🏗️ Building Heat Loss Summary
⚠️ Building permit submissions require a BCIN-stamped CSA F280 report — this calculator is a planning tool only. OntarioHeatLoss.ca delivers stamped reports in 48 hours, province-wide.
What is CSA F280-12 and Why Does Ontario Require It?
CSA F280-12 is the Canadian standard for determining the required capacity of heating and cooling appliances in residential buildings. Under Ontario Building Code Section 9.33.2.2, every new home permit submission requires a heat loss calculation performed using this methodology — and the report must be stamped by a BCIN-registered designer.
The standard uses a room-by-room approach that accounts for three components: conductive heat loss through walls, windows, and ceilings; air leakage loss based on the building envelope’s airtightness; and ventilation loss from mechanical ventilation systems including HRVs.
ICF homes and heat loss: ICF construction dramatically reduces conductive heat loss — effective wall R-values of R-28 to R-32 vs. R-20 for typical wood frame. This means smaller, less expensive mechanical systems. Model your ICF home in our ICF Energy Savings Calculator to see the long-term impact.
How to Read Your Heat Loss Results
The total design heat loss tells you the peak BTU/h your home will lose on the coldest design day of the year. Your furnace or heating system must be capable of replacing this heat continuously. The 15% safety factor is standard practice — it accounts for unusual cold snaps and system efficiency degradation over time.
A typical 2,000 sq ft ICF home in Simcoe County (design temp −21°C) might show a total heat loss of 35,000–50,000 BTU/h. A comparable wood frame home would typically be 55,000–75,000 BTU/h — explaining why ICF homes routinely use smaller, cheaper mechanical systems.
Common R-Values for Ontario New Construction
| Assembly | Minimum OBC 2024 | Typical Good Practice | ICF / High Performance |
|---|---|---|---|
| Above-grade walls | R-22 effective | R-24–R-26 | R-28–R-32 (ICF) |
| Windows (glazing) | R-2.5 (U-0.4) | R-3–R-4 | R-5–R-7 (triple pane) |
| Ceiling / attic | R-50 effective | R-60 | R-70–R-80 |
| Basement walls | R-17 effective | R-20–R-24 | R-26+ (ICF) |
| Slab-on-grade | R-10 under slab | R-15–R-20 | R-20+ (full sub-slab) |
Frequently Asked Questions
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