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Old, Metal HVAC Ducts Are Famously Inefficient And Leaky

By
Home Inspector with Jay Markanich Real Estate Inspections, LLC 3380-000723

In the good old days HVAC duct work was small, metal and did not efficiently carry air because old, metal HVAC ducts are famously inefficient and leaky.

Why?

Because there are many joints, elbows and unions that either were left with gaps, or the gaps and holes developed over time.

Additionally, they ran the ducts inside walls and ceilings.  Heated air escaped at every opportunity!

The ducts were not insulated and so they would emit heat everywhere, in addition to the heated air they blew into the house.

As time passes these same ducts would be used for air conditioning.

This was much less efficient still because air conditioning relies more on returning air than blowing lots of air out.

The returned air was not as much in volume as would be needed to efficiently cool.

That is why when newer, larger air conditioning units, and particularly heat pumps, are installed in older houses with metal ducts they are simply not as efficient as with the newer, larger, more insulated ducts and returns.

How did they solve this leaking problem?

Typically with the so-called "duct tape."

DUCT TAPE IS A MISNOMER!  IT WAS ORIGINALLY CALLED "DUCK" TAPE AND DESIGNED FOR OTHER APPLICATIONS.  ONE OF THESE APPLICATIONS WAS TO SEAL BULLET HOLES AND WRAP AMMUNITION CASES ON THE "DUCKS" (THE AMPHIBIOUS PERSONNEL LANDING CRAFTS) THAT ARE SO FAMOUSLY SEEN ON D-DAY FILMSTRIPS. 

At some point the tape became "duct" tape and its mission to fix everything was begun!  It is used now for everything!  You name it - HVAC, plumbing, electricity, roofs, fences, gutters, downspouts, household repairs - well you name it, everything!

But how inefficient and leaky are these metal ducts?

In these thermal images warmer temperatures are demonstrated by orange and yellow.

The far right shows two ducts inside the living room walls to above separate and pass through the ceiling to service two third-level bedrooms.

The center image shows one of those ceiling ducts.

And the left image is the end of the line, where the duct is converted to blow into floor register.

They are leaky!  Imagine those ducts passing air 30' or 40' or 50' or 60' from the furnace!  That's a lot of heat wasted inside wall and ceiling cavities!  The same would go for air conditioning.  It is not efficient.

Air is escaping at joints and seams.  Heat is escaping throughout the run of the duct.

The insides of the walls and ceilings are very comfy!

Today those seams and joints are better sealed.  They tape them with aluminum tape, which is more sticky and lasts longer than the old duct tape.  And many areas are painted with a latex paint, which seals everything nicely and permanently.

Inside walls and ceilings and attic spaces duct work is better insulated.  Sure, they are glorified slinkies with plastic wrap and insulation all around. 

BUT THEY AREN'T BARE METAL!

My recommendation:  sometimes the good old days aren't as good as imagined.  Especially with heating and air conditioning!  Dramatically better efficiency is achieved nowadays!  While today is not perfect, the industry uses a much Better Practice than in former times.  And the insides of walls, ceilings and attic spaces are not so comfy!

 

 

 

Posted by

Jay Markanich Real Estate Inspections, LLC  

Based in Bristow, serving all of Northern Virginia.

Office (703) 330-6388   Cell (703) 585-7560

www.jaymarinspect.com


Comments (44)

Charles Buell
Charles Buell Inspections Inc. - Seattle, WA
Seattle Home Inspector

Jay, watch out for the slippery slope of talking bad about the good ole days :)

Sep 05, 2013 06:26 AM
Jay Markanich
Jay Markanich Real Estate Inspections, LLC - Bristow, VA
Home Inspector - servicing all Northern Virginia

Glad you enjoyed it Sibley!  Stop by often!

I think they had/have the best duct tape usages ever Norman!  Not much holds up under the rodentia attack!

Charlie - I thought of you as I wrote this, always talking down yesteryear's such and so forth in favor of the now!  I thought you'd like me on your side for once!

Sep 05, 2013 06:31 AM
Donald Hester
NCW Home Inspections, LLC - Wenatchee, WA
NCW Home Inspections, LLC

Jay, I had one of these old duct running though a crawlspace (no vapor barrier) and below the duct you could see where is had been raining off the duct from condensation during cooling mode.

Sep 05, 2013 09:41 AM
Charles Buell
Charles Buell Inspections Inc. - Seattle, WA
Seattle Home Inspector

Come on Jay, you know we went to different schools together :)

Sep 05, 2013 10:13 AM
Jay Markanich
Jay Markanich Real Estate Inspections, LLC - Bristow, VA
Home Inspector - servicing all Northern Virginia

You could probably see the little trail there Don, all craters and fans!

Charlie - and I remember every day.  You still eating peanut butter and applesauce sandwiches for lunch?

Sep 05, 2013 11:09 AM
Jimmy Faulkner
Florida. Homes Realty & Mortgage - Wantagh, NY
The Best Of St. Augustine

There is a parable in the Bible that you do not replace old wineskins with new wine. The wineskins break due to the acid of the new wine just like an A/C system will force an issue with old ducts. Change everything if you can. It saves money.

Sep 05, 2013 12:09 PM
Clint Mckie
Desert Sun Home, commercial Inspections - Carlsbad, NM
Desert Sun Home, Comm. Inspection 1-575-706-5586

Hi Jay,

I had this just today. In fact it was a re inspect for the work that had supposed to have been completed. Nope nothing done. Still leaking like there's no tomorrow.

Gotta love this business.

Have a good night in Bristow.

Best, Clint McKie

Sep 05, 2013 12:20 PM
Jack O'Neal
HomeSmart Elite Group - Gilbert, AZ

Great Comment, an energy audit will help discover these issues. Every bit helps when its 113 outside.

 

Sep 05, 2013 01:38 PM
Mike McCann Nebraska Land Broker
Mike McCann - Broker, Mach1 Realty Farm & Commercial Land Broker-Auctioneer Serving Nebraska - Kearney, NE
Farm & Commercial Property For Sale 308-627-3700

Jay...it has been a few years since I saw ducts like the photo.  Used to have them running right through the ceiling of my downstairs bedroom when I was growing up!  They also are great for cobweb growing and pet spider lairs.

Sep 05, 2013 01:47 PM
MichelleCherie Carr Crowe .Just Call. 408-252-8900
Get Results Team...Just Call (408) 252-8900! . DRE #00901962 . Licensed to Sell since 1985 . Altas Realty - San Jose, CA
Family Helping Families Buy & Sell Homes 40+ Years

So what's your best advice to people with old metal ducts? Paint them? Wrap them with insulation? Use aluminum tape on all elbows & seals?

Sep 05, 2013 02:00 PM
Jay Markanich
Jay Markanich Real Estate Inspections, LLC - Bristow, VA
Home Inspector - servicing all Northern Virginia

Jimmy - that is a tall order!  But if possible it would be a good idea. 

Clint - that keeps us in business!

Jack - I do energy audits, but a thermal image sweep of a house reveals all sorts of things!

Mike - that is because of all the moving air.  Spiders build webs near moving air.

That is a hard one Michelle.  Older homes don't have the room necessary for new duct sizes.  If possible, older ducts can be sealed with aluminum tape, painted with latex or insulated.

Sep 05, 2013 06:12 PM
TeamCHI - Complete Home Inspections, Inc.
Complete Home Inspections, Inc. - Brentwood, TN
Home Inspectons - Nashville, TN area - 615.661.029

Good morning, Jay. Duct tape is good for temporary repairs and holding cars together. Other than that, it is good for the manufacturers pocket book!

Sep 05, 2013 08:10 PM
Jay Markanich
Jay Markanich Real Estate Inspections, LLC - Bristow, VA
Home Inspector - servicing all Northern Virginia

You forgot broken bones Michael.  Every household should have it for first aid.

Sep 05, 2013 08:43 PM
Andrew Mooers | 207.532.6573
MOOERS REALTY - Houlton, ME
Northern Maine Real Estate-Aroostook County Broker

Houston, we have a problem. Heat loss or air conditioning leaks due to who was the tin knocker on this heating, cooling system. And (reaching) hand me that roll of duct tape for a little razzle dazzle bailing twine, hay wire make it better not pretty  action.

Sep 05, 2013 09:23 PM
Gabe Sanders
Real Estate of Florida specializing in Martin County Residential Homes, Condos and Land Sales - Stuart, FL
Stuart Florida Real Estate

I learned that it used to be duck tape from you today!  And I love the Duck Boat tours as well, though I didn't see that much duck tape on them in Boston.

Sep 05, 2013 10:00 PM
Jay Markanich
Jay Markanich Real Estate Inspections, LLC - Bristow, VA
Home Inspector - servicing all Northern Virginia

Nice try Andrew.  Obviously you are forgetting the chewing gum.  Mint works better than fruit, by the way.

Gabe - duct tape is 110 years old!  And used for electrical applications when it first came out!

Sep 05, 2013 10:14 PM
Michael Gendreau
Edina Realty - White Bear Lake, MN
Edina Realty

good information, i did not know the info on duct tape and the current use of aluminum

Sep 05, 2013 10:18 PM
Jay Markanich
Jay Markanich Real Estate Inspections, LLC - Bristow, VA
Home Inspector - servicing all Northern Virginia

Glad you could learn something Michael!

Sep 05, 2013 10:20 PM
Scott Fogleman
Richmond, VA

Replacing the ductswhen you upgrade the unitmakes a huge difference.. Everyone shoulddo it..

Sep 05, 2013 10:50 PM
Jay Markanich
Jay Markanich Real Estate Inspections, LLC - Bristow, VA
Home Inspector - servicing all Northern Virginia

That's a tall order in older homes Scott, but that would be a great thing to do!

Sep 05, 2013 10:57 PM