Heat Loss Calculator Ontario 2026

Free CSA F280-12 Heat Loss Calculator for Ontario Building Permits

Calculate your residential heat loss accurately using the official HRAI methodology. This CSA F280-12 heat loss calculator follows the exact standards required for Ontario building code compliance (Section 9.33.2.2).

Whether you’re a homeowner, contractor, or HVAC designer, this tool helps you determine the correct furnace size and meet building permit requirements with room-by-room precision and proper air leakage calculations.

How to Use

Enter your project details, building dimensions, and R-values for walls, windows, and ceilings. The calculator automatically computes conductive heat loss, air leakage, and ventilation loads using CSA F280-12 methodology.

What You Get

Room-by-room heat loss breakdown, total design heat loss in BTU/h, and recommended furnace capacity with 15% safety factor. Results are building permit ready and code compliant.

Why CSA F280-12

This is the Canadian standard for residential heating equipment sizing. Unlike simplified calculators, this implements the full HRAI worksheet methodology accepted by Ontario building inspectors.

CSA F280-12 Heat Loss Calculator

Official HRAI Methodology for Ontario Building Code Compliance

Section 9.33.2.2
Project Information
Design Conditions (Section A)
Floor area × ceiling height
Temperature Difference (ΔT): 40°C = 72°F

Section 10: Conductive Heat Loss by Room

Instructions: Enter dimensions and R-values for each room. Heat loss calculates as: Area ÷ R-value × ΔT
Room Name Level Wall Area
(sq ft)		 Wall R Window Area
(sq ft)		 Window R Ceiling Area
(sq ft)		 Ceiling R Heat Loss
(BTU/h)

Section 11: Air Leakage Calculation

CSA F280-12 Formula: HLleak = B × LRairh × Vb × HL∆T
Where B (Imperial) = 0.018
Method Selection
Leakage Rate (from CSA Calculator)
Get this from CSA’s Envelope Air Leakage Calculator
Calculated Air Leakage
0 BTU/h
= 0.018 × 0.15 × 18000 × 72

Level Factors & Distribution

Air leakage is distributed to rooms proportionally based on their conductive heat loss and level factor.
Level Level Factor Conductive Heat Loss Air Leakage Multiplier
Level 1 (Basement) 0 0
Level 2 (Main) 0 0
Level 3 (Upper) 0 0

Section 12: Mechanical Ventilation

CSA F280-12 Formula: HLvent = C × CFM × HL∆T × (1 – E)
Where C (Imperial) = 1.08
Ventilation System
E = Apparent Sensible Effectiveness (typically 60-80%)
Ventilation Heat Loss
0 BTU/h
= 1.08 × 75 × 72 × (1 – 0)

Complete Heat Loss Summary

Room Level Conductive
(BTU/h)		 Air Leakage
(BTU/h)		 Ventilation
(BTU/h)		 Total Room
(BTU/h)

Building Heat Loss Summary

Section 10: Conductive
0 BTU/h
Section 11: Air Leakage
0 BTU/h
Section 12: Ventilation
0 BTU/h
TOTAL DESIGN HEAT LOSS
0 BTU/h
Recommended Furnace Capacity (with 15% safety): 0 BTU/h

Complete Guide to CSA F280-12 Heat Loss Calculations for Ontario Building Permits

Everything you need to know about accurate residential heat loss calculation, furnace sizing, and building code compliance in Ontario.

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Legal Disclaimer: This calculator is provided for informational and educational purposes only; we are not legally responsible for any errors, omissions, or decisions made based on these calculations—always verify results with a qualified HVAC professional and consult local building authorities before finalizing equipment selection or permit submission.

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