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

This is Part 2 of our 4-Part article that details ways to have a quieter 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.

How To Have A Quieter HVAC System

Why HVAC Systems Make Different Noises — And What You Can Do To Minimize Them.

Image Source: CanStockPhoto

Shown: High-Efficiency Gas Furnace

You’ll Have a Quieter HVAC System

With Furnace Air Filters Rated At MERV-13 Or Lower

The Minimum Efficiency Reporting Value (MERV) Rating of a filter — refers to the size of the filter’s holes where the air passes through.

Anything that restricts air flow increases air pressure on one side — and decreases it on the other side.  As air pressure increases, noise increases.

The Higher A Filter’s MERV Rating:

• The smaller the filter’s holes.
• The better it filters the air.
• The harder for the furnace blower to force air through the filter.

• This causes the HVAC System to work harder & longer, and make more noise.
• This increases cooling & heating bills.
• This wears the furnace out sooner.

The Higher A Filter’s MERV Rating:

• Return-Air (going to the furnace) air pressure becomes higher.  Higher air pressure = more noise.

• Supply-Air (coming from the furnace) pressure becomes lower.

• The higher the air pressure imbalance within the ductwork = more noise is created.

• Furnaces are not designed for high air pressure imbalances.

• 2 Furnace Manufacturers (Trane/American Standard) recommend up to MERV-13.

Furnace Air Filter MERV Rating — Filtration Efficiency

• MERV: 1 Captures <20% of airborne particles down to 3-10 microns.
• Only protects the furnace.

Image Source: Shutterstock

Shown: MERV-1 Air Filter

• MERV: 2-6  Rated “OK” For Homes.
• MERV-2–4 Captures <20% of airborne particles down to 3-10 microns.
• MERV-5:     Captures 20% (sometimes more) of airborne particles down to 3-10 microns
• MERV-6:     Captures >35% of airborne particles down to 3-10 microns

American Standard / Trane Furnaces Website Says: “Most homes are best served by a filter with a MERV-8 to 13.

• MERV 7-8  Rated “Good” For Homes.
• MERV-7: Captures >50% of airborne particles down to 3-10 microns
• MERV-8: Captures 70% of airborne particles down to 3-10 microns
• MERV-9: Captures 75% of airborne particles down to 3-10 microns
• MERV-10: Captures 80% of airborne particles down to 3-10 microns
• MERV-11:  Captures 85% of airborne particles down to 3-10 microns

The American Society of Heating, Refrigerating & A/C Engineers (ASHRAE) — Recommends A MERV-13 Filter

The Environmental Protection Agency (EPA) Recommends a MERV-13 Filter For Air-Exchange Systems (exchange indoor air with outdoor Air).

• MERV: 13 Is Rated “Best” For Homes.
• MERV-12: Captures 90% of airborne particles down to 3-10 microns –PLUS- 65% 1-3 microns.
• MERV-13  Captures 90%+ of airborne bacteria & viruses -PLUS- 85% down to 1-3 microns.

A MERV-14+ Filter Creates Too Much Air Flow Restriction — And Causes Too Much Stress On The HVAC System.

• MERV-14+ Is Rated “Too High” For Homes.
• MERV-14 Captures 95%+ of airborne bacteria & viruses -PLUS- 90% 1-3 microns.  NOTE:  MERV-14 efficiency is only +5% over MERV-13.

• MERV: 14-16: Hospital In-Patient Care (patients admitted to the hospital).
• MERV: 17-20: Hosptial surgical/operating rooms.

Sources:

• https://www.trane.com/residential/en/resources/hvac-basics/filters-help-keep-your-indoor-air-clean/
• https://nahbnow.com/2020/12/understanding-merv-ratings-and-their-impact-on-air-filtration/
• https://www.bobvila.com/articles/merv-ratings/
• https://www.allfilters.com/airfilter/mervefficiency

Will A MERV-13 Air Filter Catch Covid-19 Virus Particles?

Image Source: Shutterstock

Shown: Respiratory Droplets Moving Outward From Someone Who Coughed or Sneezed.

A MERV-13 Filter Captures 90%+ Of Airborne Bacteria & Virus Particles 3-10 Microns -PLUS- 85% 1-3 Microns.

These Airborne Virus Characteristics Also Come Into Play:

• Airborn Viral Particles are <1 micron in size.
• BUT — a virus must have a host in order to survive.
• An airborne virus’s host is a Respiratory Droplet.
• Respiratory Droplets are little balls of saliva & moisture.

Larger Respiratory Droplets:

• Size >5 microns.
• Larger droplets quickly fall downward.
• They travel up to 3-1/4 feet before falling.

Smaller Respiratory Droplets

• Size <5 microns.
• Smaller droplets quickly dry out.
• Once the respiratory droplet dries out — the virus can’t survive.

• MERV-13  Captures 90%+ of airborne bacteria & viruses -PLUS- 85% down to 1-3 microns.
• A MERV-13 Air Filter PLUS Respiratory Droplets >5 microns — dropping to the floor PLUS Respiratory Droplets <5 microns — quickly drying out = A High Degree Of Protection.

Source: National Institute Of Heath (NIH)  https://www.ncbi.nlm.NIH.gov/pmc/articles/PMC7579175/

Using a MERV-14 (or higher) Filter May Damage Your HVAC System

• Residential HVAC Furnace Blowers Are Not Designed For The Airflow Restriction Created By A MERV-14 or higher filter. 

• The higher an Air Filter’s MERV — the more force is required (from the furnace’s blower) to push air through the filter.
• The higher the MERV — the faster the filter clogs.  This places additional stress on the HVAC System.

• With a MERV-14 or higher air filter — you’re essentially clogging your HVAC system.
• A furnace blower isn’t designed to be operated under these conditions,

How Restricted Airflow Can Damage A Furnace

There are many benefits to unrestricted airflow — more than just a quieter HVAC system.

Image Source: Dreamstime

Shown: A Heat-Exchanger Is Inside Every Gas Furance

Restricted Airflow Effect On A Furnace:

• Causes the furnace to run hotter than it’s designed to. 
• Running too hot — wears out the heat-exchanger sooner.

• Reduced airflow increases cooling & heating costs. 
• Reduced airflow — wears out the furnace blower sooner.  

Click Here To See A Cracked Furnace Heat-Exchanger:  Cracked Furnace Heat Exchanger

What A Furnace Heat-Exchanger Does:

• Keeps heat & carbon monoxide (from the burners) — separated from the home’s indoor air.
• Heat & carbon monoxide (from the burners) flow inside the heat-exchanger
• The home’s indoor air flows along the outside of the heat-exchanger.

• Each time a gas furnace cycles — the heat-exchanger heats up.  At the end of the cycle, the heat exchanger cools down.
• Expansion (warming) & contraction (cooling off) causes metal fatigue.
• Reduced airflow causes the heat-exchanger to heat up more than it’s designed to.
• This causes increased expansion & contraction.
• Over time, the metal fatigue causes cracks in the heat exchanger.

• Once the heat-exchanger cracks — it has the potential to allow carbon monoxide to mix with the home’s indoor air.
• Replacing a furnace’s heat-exchanger is quite expensive.
• In most cases — a cracked heat-exchanger requires the furnace to be replaced.
• This is because heat-exchanger cracks typically happen in older furnaces — because the furnace is wearing out.

WHY?

• If the furnace is 7.5+ years old — replacing the heat exchanger is often not justified.
• This is because all other components are old and closer to failure too.

• HomeAdvisor.com says: “Replacing a furnace costs $4,625 on average.”
• HomeAdvisor.com says: “Replacing a furnace heat exchanger costs $1,500 on average.”
• If the furnace needs a blower motor in the future — it will cost $500 on average.

• Replacing the Heat Exchanger — costs 1/3 of the cost of a new furnace.
• Add a blower motor — and total costs are nearly 1/2 that of a new furnace.

• Based on Bob Vilas’ recommendation: A gas furnace that’s 7.5 years old — is at 1/2 of its average lifespan.
• Bob Vila says: “If your furnace is more than 15 years old — begin considering furnace replacement.”

Sources:

https://www.homeadvisor.com/cost/heating-and-cooling/replace-heat-exchanger/

https://www.homeadvisor.com/cost/heating-and-cooling/install-a-furnace/

https://www.homeadvisor.com/cost/heating-and-cooling/blower-motor-replacement/

https://www.bobvila.com/articles/furnace-replacement/

How Restricted Airflow Can Damage/Destroy A Central A/C Outdoor Unit

There are many more benefits to unrestricted airflow — than just a quieter HVAC system.

Image Source: Shutterstock

Shown: Frozen Central A/C Outdoor Unit

Restricted Airflow:

• Causes the A/C indoor cooling coil to run colder than designed to.  
• This causes refrigerant (that’s too cold) to return to the outdoor unit. 
• This can lead to the outdoor unit’s coil freezing too.

Click Here To See A Frozen Indoor Cooling-Coil (evaporator coil): Frozen Central A/C Indoor Cooling Coil (evaporator coil)

Note: The indoor cooling-coil is located inside the furnace or ductwork.  It can’t be seen without removing a panel

• The indoor cooling-coil removes humidity from indoor air.
• Restricted airflow causes too little air to pass through the indoor cooling coil.
• This can cause the indoor coil to freeze.

• A frozen indoor coil returns refrigerant (that’s still too cold) to the outdoor unit.    
• This can cause the outdoor unit to freeze.

• A frozen indoor or outdoor coil can damage or destroy the outdoor unit’s compressor.
• If the A/C outdoor unit freezes — its compressor (what moves the refrigerant) runs way too hot.

• Replacing a 36,000 BTU/3-Ton A/C costs an average of $3,000.
• Replacing the compressor in a 36,000 BTU/3-Ton A/C costs an average of $1,200.

• If the outdoor unit’s 7.5+ years old — replacing the compressor is often not justified.
• This is because all other components are old and closer to failure too.
• Replacing the compressor costs nearly 1/2 the cost to replace the a/c outdoor unit.
• And, many other components in the outdoor unit are old and closer to failure too.

• This is even moreso the outdoor unit is older and requires R-12 (Freon) refrigerant.
• Freon has been banned in the U.S. and recharging Freon A/C’s (built before 2010) has become quite expensive.

Sources:

** https://www.homeadvisor.com/cost/heating-and-cooling/home-ac-compressor-replacement-repair/

** https://www.centralairconditionerprice.com/

NOTES:

• Low airflow and frozen coils — can also occur due to reduced airflow because the indoor cooling-coil is clogged with accumulated dirt.
• All air filters allow some airborne contaminants through.  Over time, they accumulate on the indoor cooling coil (during A/C season).

• The moisture (from humidity removal) & accumulated dirt — provide the perfect environment for mold to establish and grow.
• Then each time the furnace blower runs — it’s blowing mold-spores throughout the home.

Click Below To See A  Clogged & Molded Indoor Cooling-Coil (evaporator coil):

Clogged & Molded Indoor Cooling Coil (evaporator coil).

Noises Coming From Ductwork

It’s common to hear noises coming from ductwork (moreso if it’s metal).  While some noises are normal, other noises result from issues with the ductwork

Image Source: Shutterstock

Shown Above: Rigid Metal Ductwork

Image Source: Shutterstock

Shown Just Above: Flexible Ductwork

It’s Common To Hear The Swooshing Sound Of Moving Air 

At Supply-Air Vents — bringing air from the furnace.

At Return-Air Grilles — taking air to the furnace. 

Note: If Ductwork Noise Suddenly Becomes Louder — It’s Likely Due To A New Airflow Restriction Somewhere Within The HVAC System.

• The #1 Reason Is A Clogged Furnace Air Filter.

• Another Common Cause Is Closing Too Many Air Vents.
• No more than 10% of all air ducts can be kept closed.
• When more vents are closed — air pressure throughout the supply-air ductwork increases.
• This increases noise.

• The HVAC System was designed & installed to be operated with all air vents fully open.
• Reducing airflow causes the furnace to heat up more than it’s designed to.
• This creates notable stress on a (gas) furnace’s heat-exchanger — causing it to fail sooner.

TIP: It’s likely the money you saved by closing off too many vents — will be spent replacing the furnace sooner.

NOTE: If you own a Variable-Speed HVAC System — You Can Close Off As Many Vents As You Want.

• A Variable-Speed HVAC System slows the furnace blower to accommodate reduced airflow.
• Note: 90%+ of HVAC Systems Are Not Variable-Speed.

If All Air Vents Are Open & The Air Filter’s Clean

A New/Increased Noise Means Something Within The Ductwork Has Changed.

• If you have flexible ductwork — it’s possible it’s become squeezed or crimped.
• If you recently had workers in the attic — they may have damaged flexible ductwork.

Note: This seldom occurs with rigid, metal ductwork.

If You Have A Brand New HVAC System — That Makes More Noise Than The Old System

Consider This: Water flowing through a garden hose with the end open. The water flows out in a gentle stream because it’s under low pressure. Put your thumb over part of the end of the hose, and the water sprays farther.   That’s because higher pressure is pushing the water farther.  The more the end of the hose is blocked, the more noise the water makes coming out.

Increased Airflow = Increased Air Pressure =  Increased Noise.

IF Your New HVAC System Moves More Air Than The Old One:  The existing ductwork is too small to accommodate the increased amount of air movement.  Increased air pressure in ductwork creates more noise.

• If existing ductwork wasn’t replaced or adapted — changes may be needed to accommodate increased airflow.

• It’s possible that the new flexible ductwork wasn’t installed properly.

• Flexible ductwork requires many support straps to keep it from sagging.  If it sags, air movement becomes restricted, and more noise is heard.

• Flexible ductwork can also be bent too tight where it changes direction.  More than 90-degree bends restrict airflow, increasing noise.

Click Here To See Properly Installed Flexible Ductwork: Professional Builder.com Properly Installed Flexible Ductwork

NOTE: Scroll Down (in the article) To See More Photos Of; Properly Installed AND Poorly Installed Flexible Ductwork.

Note: Professional Builder is a trade magazine for new home builders.

Flexible Ductwork Installation Practices

Image Source: Amazon Embedded Link

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

SHOWN: Cut-Away Diagram Of Flexible Ductwork: 1. Outer Jacket (silver) 2. Fiberglass Insulation (yellow) & 3. Inner Core(silver with ribs).

These Flexible Ductwork Installation Practices Inprove HVAC System Performance. 

And You’ll Have A Quieter HVAC System

Done Poorly — There Will Be Increased Air Resistance/Turbulence.

Increased Air Resistance/Turbulence = Lower Airflow & Increased Air-Movement Noise.

Copy The Link Below Into Your Browser For A Complete Flex Duct Installation Guide: http://www.atcoflex.com/uploads/4/9/4/0/49403973/installinstructions.pdf

Ductwork Length:  It’s not to be longer than required — and pulled tight.

Ductwork Sealing:

BOTH Must Be Sealed:

• Ductwork’s outer Vapor-Barrier Jacket.   It’s silver and wraps around the insulation.
• Ductwork’s inner core.  It’s silver and ribbed.  This is where the air flows through.

Image Source: Amazon Embedded Link

Ductwork Supports:

• The sag allowed between supports must not exceed 1/2 inch per 1 foot of ductwork.
• Flex duct must not be supported by anything that’s less than 1/1-2 inches wide.
• Maximum spacing between supports — must be in compliance with manufacturer’s installation specifications.

• How steep ductwork bends are (never to be more than 90 degrees).
• Gradual bends (up to 90 degrees) reduce air restriction/turbulence.

• Flex duct must never be crimped or compressed.

• Seal flexible ductwork’s inner Flexible Core (what the air flows through).

Ductwork Routing:

• Flex duct must not be supported by anything less than 1/1-2 inches wide.
• It’s OK for flexible ductwork to rest upon ceiling joists (what the rooms’ ceiling drywall is attached to from below).
• It’s OK for flexible ductwork to rest upon the bottom of attic trusses (attic truss bottoms are the ceiling joists).

Image Source: Shutterstock

Shown Just Above: Flexible Ductwork Routed Upon The Bottoms Of Attic Trusses

NOTES:

• Most new homes are built with attic trusses.
• Attic trusses are pre-built and have 3 sides.
• The roof is nailed to the upper 2 (angled) sides.
• The rooms’ ceiling drywall is nailed to the bottom side.

• Attic trusses have metal braces installed where two boards meet.  This makes them very strong and stable.

Image Source: Shutterstock

SHOWN: Attic Trusses

Can You Use The Existing Ductwork When Installing A New Furnace?

Flexible ductwork results in a quieter HVAC System.

Image Source: Shutterstock

Shown: Rigid, Metal Ductwork

• Yes: If the new furnace has similar airflow (if the ductwork was sized correctly when installed).
• Yes: If the new furnace has higher airflow — If The Existing Ductwork Can Be Adapted As Needed. 
• Your HVAC Contractor can tell you the airflow for the old and new furnaces.

TIP: A High-Efficiency Furnace (with similar airflow) Doesn’t Require New Ductwork.

• Higher efficiency does not mean the furnace has higher airflow.
• Higher efficiency only indicates how well the furnace removes heat from its exhaust.
• Today’s most efficient gas furnace = 98.7%.   This means only 1.3% of the heat generated is vented out with the exhaust.
• In the northern U.S. — the minimum efficiency allowed = 90%.

• In the southern U.S. — the minimum efficiency allowed = 80%.
• This means 20% of the heat generated is vented out with the exhaust.
• Standard efficiency (80%) gas furnaces don’t remove any heat from their exhaust.

TIP: Keeping Your Existing Ductwork?  Have It Cleaned & Sealed.

Click Here To See Before & After Ductwork Cleaning Photos: Before & After Ductwork Cleaning

TIP: Have existing ductwork Cleaned & Sealed when installing a new furnace.   The older ductwork gets — the dirtier it becomes, and the more air it leaks.

TIP: Ductwork cleaning should be done at least every 10 years — because tremendous amounts of dust collect in the return-air ducts (taking air TO the furnace).

TIP: Cleaning should be done more frequently in homes with several occupants and/or shedding pets.

TIP:

• Many Ductwork Cleaning Companies offer optional Ductwork Sealing.
• If you want Ductwork Sealing — check if the company offers sealing before hiring them.
• After cleaning — a sealer product is pushed through the ductwork (with high air pressure).
• The sealer naturally exits at leaks.
• The sealer builds up around the leaks until they’re sealed.

** Source: https://www.energystar.gov/products/most_efficient/furnaces

A Side Note:

In 2020 — Texas Had 1,053 Tornado Reports

Source: https://www.ncdc.noaa.gov/sotc/tornadoes/202013

Tornado Formation & Updraft:

• Tornadoes can form when warm, humid air collides with cold, dry air.
• The warm air rises through the colder air — creating an updraft.

• During the formation of a tornado — the updraft tilts from horizontal (rotation) to vertical.
• Updraft accelerates in speed as it rises.
• Increasing speed causes vertical stretching — and the tornado forms.
• A tornado can be described as a: “rotating updraft“.

Copy The Link Just Below Into Your Browser For A Detailed Explanation Of Super Cell Thunderstorms.  They are what spawn tornadoes.

https://www.weather.gov/media/lmk/soo/Supercell_Structure.pdf

A Tornado’s Updraft Often Lifts A Home’s Roof Off.

Here’s How To Prevent/Reduce This Possibility

Image Source: Shuttertock

SHOWN: Common Tornado Damage — Roof Is Gone.

Additional Tornado-Damage Protection Can Be Achieved By Installing Hurricane Clips

They Attach A Home’s Roof To Its Walls.

Image Source: Shutterstock

SHOWN: A Hurricane Clip Installed

Watch A Tornado Lift A Home’s Roof Away

Image Source: YouTube Embedded Video

SHOWN: A Tornado Lifts A Home’s Roof Off  (At Time: 0:45 / 1:14).

Note: The Outside Walls Start Falling Only Moments Later.

• Once the roof is gone, it’s likely the walls will come down.
• The walls depend on the roof for structural stability.
• With that stability gone — high winds are almost certain to damage/destroy outside walls.
• Once outside walls are compromised — high winds can damage/destyroy inside walls.

Source: https://sites.psu.edu/pmarkowski/how-tornadoes-form/

Hurricane Clips Can Help Prevent A Tornado Lifting The Roof Off A House.

Copy This Link Into Your Browser To See Hurricane Clips — That Attach The Roof To The Walls.

• https://plasticinehouse.com/how-to-install-hurricane-ties/

Copy This Link Into Your Browser To See Wall Anchors That Attach The Walls To The Foundation.

• https://www.coastalhomeplans.com/hurricane-strap-tie-primer-building-in-high-wind-zones/

Notes:

• Unless Building Code Requires More — attic trusses are typically only nailed to the walls.

• Texas Does Not Require Hurricane Clips.
• Texas leaves that decision to municipalities.
• Houston, TX requires them.
• There are likely also other coastal cities that do too.

• Joplin, Missouri began requiring hurricane clips — after the devastating tornado in spring of 2011.
• Florida (since 2002) & Louisana require hurricane clips.
• Florida also requires retrofitting existing homes with hurricane clips.

Source: https://coastalresilience.tamu.edu/home/introduction-to-coastal-resilience/legal-framework-for-planning/stateandlocal/building-codes/

This was Part 2 of our 3-Part article that details many ways to have a quieter 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 Rowlette, TX; Wylie, TX; and Murphy, Texas.  We service all homes in southern Collin County, TX & northeastern Dallas County, TX with no additional travel charge.