How To Have A More Quiet HVAC System – Part 3 (of 3)


Click Here For Part 1 Of This Article: Make HVAC System Quieter

This is Part 3 of our 3-Part article — Describing Many Things You Can do To Have A More Quiet HVAC System.  Al’s Plumbing, Heating & A/C, in Plano, Texas provides full-service plumbing maintenance, repairs, and replacements for every plumbing component in your home.  Al’s sells and installs Rheem Professional Series gas & electric water heaters, and tankless water heaters.  Al’s Plumbing, Heating & A/C is near your home in McKinney TX; Allen, TX; and Plano Texas. We service all homes in southern Collin County, TX & northeastern Dallas County, TX with no additional travel charge.

Al’s also provides maintenance & repairs for all brands of Central A/C, Gas & Electric Furnace, and Heat Pumps.  Additionally, we sell and install new HVAC Systems from American Standard (same company as Trane), Ameristar, and Coleman HVAC (same company as York HVAC).

Another Common Source Of HVAC System Noise Is

1 Central Return-Air Duct (serves the entire house).

(More Air Flow At 1 Location = More Noise)

Shown: 1 Central Air Return Grille.  These Are Quite Large — Because They Serve The Entire Home.

There Will Be Notable Noise Near This Grille — Because ALL Air (returning to the furnace) Passes Through It.

Central air returns are common in newer homes.  Instead of providing an air-return in each room (except kitchen and baths) — only one return is installed.  It’s an acceptable (but not optimal) way to configure an HVAC System — it’s done as a cost-cutting measure.

  • The location of this return-air duct may create a noise problem.
  • If it’s in a hallway or foyer, the noise is less likely to be an issue.
  • If it’s near bedrooms, or a room where TV is viewed — it can be a nuisance.
  • Each time the HVAC System turns on or off — the TV’s volume must be adjusted.
  • Just Below — we discuss several ways to reduce the noise created by a 1 Central Air-Return.
  • These same efforts can also be used on single-room returns as well.
  • In some cases, the only real solution is to relocate the return-air duct.


heat vent register cover

  • Supply-Air Duct (brings air from the furnace). 
  • Its cover is called a: “Register”. 
  • It has a louver/damper to control airflow.
  • In DFW — most are in the ceiling because ductwork is commonly in the attic.

hvac return air grille

  • Return-Air Duct (takes air to the furnace). 
  • The one shown just above is a single-room air return.
  • Its cover is called a: “Grille” 
  • These smaller air-returns are located in every room (except kitchen & baths) — and serve only 1 room.
  • This is the better way to provide Return-Air to the furnace.
  • No shut-off louver.
  • Return-Air ducts are never to be shut off.

  • Central Return-Air Duct (takes air to the furnace).  
  • The one shown just above is a Central Air Return that serves the entire house.
  • Its cover is called a: “Grille”  
  • Central return air ducts create notable noise — due to the amount of air movement at 1 location.
  • It’s also common for the central return air duct to be located directly below/ above the furnace.  Especially if the furnace & ductwork are in the attic.
  • This configuration also allows the furnace’s operating-noises to be heard.

Click Here To See A Central Return-Air Duct Below Furnace (furnace located inside the home).

Click Here To See A Central Return-Air Duct In A Ceiling (furnace located in attic)

There Are 2 Sources Of Noise Coming From Every HVAC System:

Resolve Some Of The Issues Below — And You’ll Have A More Quiet HVAC System

  • Operating Noise: Is made by HVAC components.
  • Most Indoor Noise comes from the furnace’s blower + the ductwork.
  • 80% efficient furnaces (allowed in the southern U.S.) — you may also hear; the exhaust-venting motor & burners igniting.
  • 90% efficient furnaces (required in the northern U.S.) — you won’t hear; the exhaust-venting motor or burners igniting.
  • Airborne Noise: Is created by moving air.
  • TIP: Noise travels through the air.  Where you hear the noise may not be where it originates.

TIP: Closing off more than 10% of Supply-Air Ducts increases air-pressure throughout the ductwork.  More air-pressure = more noise.

An Expensive Way To Have A Quieter HVAC System.

  • Note: 90%+ of HVAC Systems are single-speed.
  • Replace an existing HVAC System with a Variable-Speed System.
  • A Variable-Speed Furnace Blower adjusts its speed — based on the amount of air-flow the ductwork configuration and settings can currently accommodate.
  • This allows as many supply-air vents (to be closed) — as the homeowner desires.
  • With a single-speed HVAC System (90%+ are single speed) — no more than 10% of ducts can be closed without adversely affecting HVAC System performance.

Low-Cost Ways To Reduce Central Air-Return Noise

TIP: Combining Solutions May Further Reduce Noise.


1. Replace The Return-Air Duct’s Grille — With One That Holds An Air Filter.

If You Have A Central Air-Return Duct — This Is The Easiest Way To Have A More Quiet HVAC System.

It’s often possible to replace the existing Return-Air Grille with one that holds a filter.   TIP: It’s OK if the new grille is larger than the ductwork’s opening.

  • The filter at the grille helps muffle noise.
  • This also eliminates going into the attic to change filters.

Image Source: Embedded Link

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Shown:  Return-Air Filter Grille

2. Change The Central Return-Air Grille To Eggcrate Style

The More Obstructions A Return-Air Grille’s Cover Has — The More Air Turbulence & Noise It Will Generate.


Egg-Crate Return-Air Grills Come In Many Sizes –The One Shown Below Is 24″ X 24″.

The Company That Sells This One — Has 10 Sizes Available.


NOTE: The Benefit Of Eggcrate Return-Air Grilles Is Their Desing Minimizes Air-Flow Restriction.

Thus more air-restriction(s) — the more (air movement) noise is generated.  

Image Source: Embedded Link

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SHOWN: 24X24 Inch Central Return-Air Grille

NOTE: On Amazon — This Particular Product Is Rated At 4.5 (out of 5).  When This Was Written — There Were nearly 850 Reviews.

3. Line The Return-Air Ductwork (that you can easily get to) With A Sound-Deadening Material.

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SHOWN: Noise Insulation (Sold in either 10 or 18 Square Feet)

(22 mm of Butyl Rubber (odorless & synthetic) — With A Foil Surface).

NOTE: On Amazon — This Particular Product Is Rated At 4.7 (out of 5).  There Were Nearly 5,200 Reviews (when this was written).


This Product’s Noise-Reduction Expectation — Base On Scientific Studies (Links Provided):

Foil-Faced + 2 mm of Butyl Rubber — Reduces Noise By Nearly -5.5 db.

That’s -25% less noise (volume) — as perceived by our ears.  NOTE: This Is Based On: -10 db = -50% of the noise volume — as perceived by our ears.



4. Sometimes The Duct Can Be Made Larger. 

  • A larger opening duct allows for slower air-movement speed.
  • A larger duct creates less air flow restriction.
  • Slower moving air makes less noise.

5. Add An Additional Air-Return Duct.

  • An additional return-air duct can often be installed.
  • In some cases, it can be connected directly to the existing return-air ductwork.
  • Two openings (on the same duct) — reduces the amount of air movement at each opening.
  • Less air movement = less noise at each duct.
  • A second return air duct — is best installed where noise is less of an issue (such as a hallway or foyer).

Older DFW Homes

Return-Air Pathway From Bedrooms (when the door’s closed)

Many older DFW homes also have central air returns.  Unlike newer homes, in older DFW homes, return-air from bedrooms must pass under the door.  In newer DFW homes, an “air-transfer grille” is installed above the door (eliminates the need for air to travel under the door).   With DFW being a cooling-climate, an opening above the door is preferred.

Older DFW Homes’ Return-air (coming from bedrooms) — passes under the door (when the door’s closed). 

  • A 1/2″ gap, between floor coverings and door — allows for return-air to exit the bedroom when its door is closed.
  • If thick carpet & pad are present — the gap under the door is often too narrow.
  • This reduces the HVAC System’s ability to properly heat & cool bedrooms (when the door’s closed).


  • If there is less than a 1/2″ gap between bedroom doors & floor coverings — one solution is to cut bedroom doors shorter.
  • Creating a larger gap (>1/2″) isn’t needed, nor wise.
  • A larger gap allows light to enter under the door — plus privacy & noise concerns may arise.

For Souther/Cooling Climates

A Better Solution: Install A Retrofit Air-Transfer Kit Above Bedroom Doors.

This Is Because Removing Warm Air During Summer — is more of an issue than removing cold air in winter.

Image Source: Embedded Link

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SHOWN: Honeycomb-Style Air-Transfer Kit (includes the 3 parts shown)


NOTE: The Reason We Show The Honeycomb-Style Air-Transfer Kit — is because they reduce the amount of noise and light that can enter the room (when the door’s closed) — as compared to simply cutting a hole and putting a grille on each side.

Copy The Link Below Into Your Browser To See An Air-Transfer Grille Installed Above A Bedroom Door:


  • Most bedroom doors are 32″ wide.
  • There’s typically a (vertical) piece of lumber centered within the space above the door.
  • Avoid removing lumber inside walls.  It’s there to support the weight of the house.

TIP: Buy An Air Transfer-Grille That’s 14″ Wide Or Less — so it can fit on either side of the vertical piece of lumber

NOTE: For Older Homes In Heating/Northern Climates

If A Bedroom Doesn’t Have An Air-Return.

Because Our Articles Are Written For The Dallas-Ft Worth Texas Area — Our Focus Is For Homes In Southern/Cooling Climates.

In this case —  we also include a better solution for heating/northern climates’ bedrooms (than cutting doors shorter).  This is because the Air-Transfer Grille shown below reduces the amount of noise and light that can enter the room (when the door’s closed) — as compared to cutting doors shorter.     It’s notably easier to cut the doors shorter — if noise & light entering the bedroom(s) isn’t an issue.

A Retrofit, In-Door, Air-Transfer Grille — Designed Designed To Be Installed In The Door (NO Honeycomb Insert). 

18″ Wide X 5″ Tall. 

Image Source; Embedded Link

Shown: In-Door Air Transfer Grille (includes both sides as shown).  Also available in white.

Click On Image To; View Product, Read Details, or Purchase From

NOTE: There Is No HoneyComb Insert For This Product.


A Retrofit, In-Door, Air-Transfer Grille — WITH Honeycomb Insert

27″ Wide X 4.75″ Tall. 

This product is more expensive than the one shown above.

Because It Has A Honeycomb Insert (to reduce noise & light transfer into the bedroom) — Plus It’s Wider.

TIP: A Honeycomb Insert Notably Reduces Noise & Light Transfer Into The Bedroom.

Shown: In-Door Air Transfer Grille (includes both sides as shown + Honeycomb Insert).  Also available in white.

This Item Rated 4.5 Stars (out of 5) — With 315 Reviews (when this was written).

Click On Image To; View Product, Read Details, or Purchase From

NOTE: HoneyComb Insert Included With This Product.

NOTE: This Product Comes In Various Quantities.  To Buy 1 — click on the appropriate box.


TIP: Air Transfer Grilles Designed For Walls — Are Too Thick For Doors. 

TIP: Air Transfer Grilles Designed For Designed For Doors — Are Too Thin For Walls.