Quietest High Efficiency Gas Furnaces

What are the Quietest High Efficiency Gas Furnaces in the Builder Grade Tier?

Lennox ML180V and ML180E:
Features: These models, while not the top-tier, incorporate some features that contribute to quieter operation. The ML180V uses a variable-speed fan motor, which can help reduce noise levels compared to single-speed motors. However, they do not have the advanced SilentComfort technology found in higher-tier models.
Limitations: These models are 80% efficient and do not have the same level of sound-reducing features as higher-tier Lennox models.
Trane 96 Single-Stage Gas Furnace:
Features: This furnace has an AFUE rating of up to 96%, making it a high-efficiency option. While it is not specifically marketed as the quietest, it has an insulated cabinet which helps in reducing noise levels.
Limitations: It is a single-stage furnace, which may not be as quiet as two-stage or variable-speed models.

Variable-Speed Blower Motors:
These motors can operate at lower speeds for most of the heating cycle, reducing noise levels. For example, Lennox’s SilentComfort technology utilizes variable-speed motors that ramp up gradually, eliminating the sudden “kick” or blast of air upon startup.
Sound-Reducing Designs:
Insulated Cabinets: Many high-efficiency furnaces come with insulated cabinets that help in reducing the operational noise.
Sound Enclosures: Higher-tier models like the Lennox SLP98V have patent-pending sound enclosures and special sound-absorbing insulation to further reduce noise.
SilentComfort Technology:
This technology, exclusive to Lennox, includes features like variable-speed motors and sound-absorbing insulation, making furnaces significantly quieter.

Proper Installation and Duct Design: Proper installation techniques and duct design can significantly minimize noise levels. Ensuring the return air duct is at least 6 feet long with multiple turns can reduce noise. Also, avoiding direct return openings into the furnace closet can help.
Upgrade Consideration: While upgrading to a higher tier can provide enhanced quietness, it may not be financially justifiable if proper installation and duct design can achieve similar results. However, if quiet operation is a top priority, models like the Lennox SLP98V offer substantial noise reduction.

Duct Sizing: Proper duct sizing is crucial for minimizing noise. Oversized ducts can lead to lower airflow velocities, which reduce noise. Conversely, undersized ducts can cause higher velocities and increased noise.
Return Air Duct: A return air duct with at least 6 feet of length and multiple turns can help absorb sound, reducing the overall noise level of the furnace.

Decibel Levels: The quietest furnaces, such as the Lennox SLP98V, are at least 50% quieter than competitors, with sound levels significantly lower than conventional single-stage furnaces.
AFUE Ratings: High-efficiency furnaces have AFUE ratings of 90% or higher, but even 80% efficient models can be quiet if properly installed and designed.