Tool · Rough furnace sizing
What size furnace might my house need?
A screening range from floor area and insulation. This tool is deliberately simple and is NOT a heat-loss calculation: Canadian sizing practice (and manufacturer product data) requires the design heat loss, and the real number comes from BC Wide's assessment.
Why the real calculation matters
- Two houses of the same area can differ by a factor of two in design heat loss.
- Manufacturer product data (quoted across this site) warns that excessive oversizing can shorten furnace and vent life, and that none of its sizes may be used where the heating load is very low.
- The furnace must also fit the ducts: airflow at rated static pressure is half the sizing question.
Methodology: GasFurnace.ca screening model (this page), disclosed here with its limits. Certified sizing follows CSA F280 and the manufacturer's product data; BC Wide's assessment performs both. Page checked 2026-09-07.
Use the range, then stop guessing
No furnace should be quoted from this screen. The assessment measures the house, the ducts and the design conditions — that is what the proposal should be built on.