Glossary · Heating, cooling & ventilation
Mid-efficiency furnace
Also called: mid-efficiency · 80% furnace · non-condensing furnace · mid-efficiency boiler
A non-condensing gas or oil furnace, around 80% efficient, that sends its exhaust up a chimney; most new gas furnaces sold in Canada must now be condensing.
What it means
Mid-efficiency furnaces were the standard upgrade before condensing models: they don't recover the heat in their exhaust's water vapour, so roughly a fifth of the fuel's energy goes up the flue. Since July 3, 2019 most new gas furnaces sold in Canada must reach 95% AFUE, which only condensing furnaces do, while the US minimum is still 80%. NRCan notes that after major air sealing a mid-efficiency furnace runs less often, so its chimney can get colder between firings and draft poorly.
Why it matters in an audit
If your mid-efficiency furnace is nearing replacement, an audit helps you compare a condensing furnace, a heat pump or a dual-fuel system for your home.
Typical numbers
Reference values with their sources. Your energy advisor’s report gives the figure for your own house.
| What | Value | Source |
|---|---|---|
| Canada, new gas furnaces made on or after July 3, 2019 | 95% AFUE minimum; 80% allowed only for relocatable-building and replacement non-condensing furnaces | natural-resources.canada.ca ↗ |