An 80% furnace uses open combustion to generate energy from natural gas. In other words, it sucks air from the surrounding area. A 95% furnace doesn’t do that – it uses sealed combustion, a process by which the furnace sucks in air from the outdoors.

How does a 95 furnace work?

An 80% furnace uses open combustion to generate energy from natural gas. In other words, it sucks air from the surrounding area. A 95% furnace doesn’t do that – it uses sealed combustion, a process by which the furnace sucks in air from the outdoors.

How do energy efficient furnaces work?

Condensing Gas Furnace: A high-efficiency furnace (90% AFUE or higher) utilizes a second heat exchanger to heat the air from condensed exhaust gases in order to reach higher efficiencies. A high-efficiency condensing furnace requires specialized venting.