Carrier Infinity Series furnaces, Lennox Signature variable-capacity furnaces and Trane XC95 variable-speed modulating furnaces are some of the quietest gas furnaces available, as of 2015. These furnaces are also highly efficient due to the use of sealed combustion chambers.
The Lennox SLP98V variable-capacity furnace is the quietest high-efficiency furnace based on its sound level while operating at steady, low-fire and high-fire states when compared to leading competitors, as stated by the official website. It earned the Energy Star Most Efficient label in 2014 with 98.2 percent efficiency, and its SilentComfort technology reduces sound levels with noise-absorbing materials and innovative engineering.
The Infinity 98 furnace with Greenspeed intelligence is a variable-speed gas furnace that has also earned the Energy Star Most Efficient label with up to 98.5 percent efficiency, and the ECM blower motor and insulated cabinet help to reduce sound levels. The furnace also uses tight temperature adjustments to allow the unit to operate longer at a lower capacity.
The Trane XC95 is an Energy Star-rated furnace with up to 97.3 percent efficiency, and its ComfortLink II communication feature lets it connect with other components of a smart heating system. The furnace features an insulated cabinet, a 24-volt fuse for protection, a silicon nitride hot surface igniter and in-shot burners.