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Old, Metal HVAC Ducts Are Famously Inefficient And Leaky

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!

 

 

 

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


Comment balloon 44 commentsJay Markanich • September 05 2013 01:50AM

Comments

Jay: Excellent examples of how heat and cool air is lost which costs the user a lot of money over time. Better to get updated equipment. Oh, and use the "duck" tape for other things.

Posted by Hella Mitschke Rothwell, Hawaii & California Real Estate Broker ((831) 626-4000) over 7 years ago

Thanks Hella.  Maybe the tape can now finally be used to corral those ducks!

Posted by Jay Markanich, Home Inspector - servicing all Northern Virginia (Jay Markanich Real Estate Inspections, LLC) over 7 years ago

I wonder if Uncle Bob knows about the aluminum tape?  We may have a new mission in life.  That is to change out all of the old duct AKA (duck) tape he's put into place.  Thanks Jay enjoy the day :)

 

Posted by James Dray, Exceptional Agents, Outstanding Results (Fathom Realty) over 7 years ago

Good morning, Jay.... ditto to what Hella said.... and there's nothing like baseboard forced hot water heat and a separate system with ductwork for air conditioning....that's the right way to do it, in my opinion.

Posted by Barbara Todaro, Previously Affiliated with The Todaro Team (RE/MAX Executive Realty - Retired ) over 7 years ago

Aluminum tape is the norm now James.  It's hard to remove the old duct tape and replace it - too much residue.

Barbara - yes, that's a good system.  That way the ducts are sized for the AC system needs.

Posted by Jay Markanich, Home Inspector - servicing all Northern Virginia (Jay Markanich Real Estate Inspections, LLC) over 7 years ago

Energy efficiency wasn't such a consideration in the "olden days" ...it sure is...and should be now !

Posted by Sally K. & David L. Hanson, WI Real Estate Agents - Luxury - Divorce (EXP Realty 414-525-0563) over 7 years ago

Prior to 1973 and the oil embargo, insulations wasn't a big consideration either S&D.

Posted by Jay Markanich, Home Inspector - servicing all Northern Virginia (Jay Markanich Real Estate Inspections, LLC) over 7 years ago

Jay, OK, but I love duct tape, duck tape, whatever. I think it can be used for almost everything, LOL. And now they have leopard print duct tape. Come on... what's better than that?

PS, this is great information, even if you slighted my most favorite thing in the world.. next to cows that is.

Posted by Andrea Swiedler, Realtor, Southern Litchfield County CT (Berkshire Hathaway HomeServices New England Properties) over 7 years ago

Andrea -you forget tying your turkey together so it cooks evenly.  Forget that roaster string.

Posted by Jay Markanich, Home Inspector - servicing all Northern Virginia (Jay Markanich Real Estate Inspections, LLC) over 7 years ago

It is best to update the ducting when installing a new AC/Heat unit from my experiences

Posted by Harry F. D'Elia III, Investor , Mentor, GRI, Radio, CIPS, REOs, ABR (RentVest) over 7 years ago

Thanks Harry.  In existing homes, particularly older ones, that is a very difficult thing to do.

Posted by Jay Markanich, Home Inspector - servicing all Northern Virginia (Jay Markanich Real Estate Inspections, LLC) over 7 years ago

Jay, imagine how much energy could be saved by buttoning up these systems. Unfortunately, as you stated it's a difficult thing to do on older homes. We could do our best to seal up areas we can see.

Posted by Michael Setunsky, Your Commercial Real Estate Link to Northern VA over 7 years ago

That would be a small percentage Mike, as you obviously understand.  Energy losses from these older systems are huge and incalculable.

Posted by Jay Markanich, Home Inspector - servicing all Northern Virginia (Jay Markanich Real Estate Inspections, LLC) over 7 years ago

Great comments here about the inefficiencies of metal duct work.  If not metal, what are people using in place of that?

Posted by Matt Kombrink, Your #1 Source For Real Estate (RE/MAX All Pro) over 7 years ago

I say in the post Matt.  Ducts are glorified slinkies, with plastic wrap and insulation.

Posted by Jay Markanich, Home Inspector - servicing all Northern Virginia (Jay Markanich Real Estate Inspections, LLC) over 7 years ago

Jay -- from the looks of the pictures provided, it seems like at least half the heat is being used before it gets to the desired destinations.  Then again, the runs in the ceiling/floor would help keep the floors warm for when people have to walk on them early in the morning. 

Posted by Steven Cook (No Longer Processing Mortgages.) over 7 years ago

It's hard to calculate a percentage Steven, but it's a lot!  And that would be a small section of heated floor, and not getting very hot because it's under carpeting anyway.

Posted by Jay Markanich, Home Inspector - servicing all Northern Virginia (Jay Markanich Real Estate Inspections, LLC) over 7 years ago

Jay, I grew up in a house built in the mid 1950's with metal ductwork everywhere. The only "benefit" was that the basement stayed really warm in the winter because of all the lost heat!

Posted by Tom White, Franklin Homes Realty LLC, Franklin TN (Franklin Homes Realty LLC (615) 495-0752 or www.FranklinHomesRealty.com) over 7 years ago

Learned something new today; I thought that duct tape originated for use on ducts. 

I just love those thermal images Jay!

Posted by Tom Arstingstall, General Contractor, Dry Rot, Water Damage Sacramento, El Dorado County - (916) 765-5366, General Contractor, Dry Rot and Water Damage (Dry Rot and Water Damage www.tromlerconstruction.com Mobile - 916-765-5366) over 7 years ago

Makes me want to evaluate my duct work and see how much heated/cooled air I'm losing. My house was built in the 70's.

Posted by Suzanne Otto, Your Montgomery County PA home stager (Six Twenty Designs) over 7 years ago

thanks Jay for the great information.  I intend to pass it on.  Great images.

Posted by Susan Jackson (America's Network Realty Group, Inc) over 7 years ago

The silver lining Tom!  Not bad!

AD Model - nope!  It actually originated in 1902 to be used for knob and tube wiring!  It has morphed many times over the centuries!  I have a book called "Did Monkeys Invent the Monkey Wrench?" and love it!  You would love it too!  Get me your address and I will make you a special gift recipient.

Suzanne - you need a thermographer to come over and have a peek!  They aren't all as cute as I am, but all thermographers are cute.

Susan - great!  That's what this thing is all about.

 

Posted by Jay Markanich, Home Inspector - servicing all Northern Virginia (Jay Markanich Real Estate Inspections, LLC) over 7 years ago

great info. thanks!

Posted by Sibley Poland, 15 Years of Professional Experience (RE/MAX Stars Realty) over 7 years ago

Jay, I have to agree, the duct tape should be left for our professional engineers an the Red/Green Show, but the flexible ducting sure doesn't hold up to pesky rodents wanting to creat havoc in an attic.

Posted by Sandy Padula and Norm Padula, JD, GRI, Presence, Persistence & Perseverance (HomeSmart Realty West & Lend Smart Mortgage, Llc.) over 7 years ago

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

Posted by Charles Buell, Seattle Home Inspector (Charles Buell Inspections Inc.) over 7 years ago

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!

Posted by Jay Markanich, Home Inspector - servicing all Northern Virginia (Jay Markanich Real Estate Inspections, LLC) over 7 years ago

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.

Posted by Donald Hester, NCW Home Inspections, LLC (NCW Home Inspections, LLC) over 7 years ago

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

Posted by Charles Buell, Seattle Home Inspector (Charles Buell Inspections Inc.) over 7 years ago

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?

Posted by Jay Markanich, Home Inspector - servicing all Northern Virginia (Jay Markanich Real Estate Inspections, LLC) over 7 years ago

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.

Posted by Jimmy Faulkner, The Best Of St. Augustine (Florida. Homes Realty & Mortgage) over 7 years ago

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

Posted by Clint Mckie, Desert Sun Home, Comm. Inspection 1-575-706-5586 (Desert Sun Home, commercial Inspections) over 7 years ago

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

 

Posted by Jack O'Neal (HomeSmart Elite Group) over 7 years ago

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.

Posted by Mike McCann - Nebraska Farm Land Broker, Farm Land For Sale 308-627-3700 or 800-241-3940 (Mike McCann - Broker, Mach1 Realty Farmland Broker-Auctioneer Serving Rural Nebraska) over 7 years ago

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?

Posted by MichelleCherie Carr Crowe Just Call...408-252-8900, Family Helping Families Buy & Sell Homes 40+ Years (Get Results Team...Just Call (408) 252-8900! . DRE #00901962 . Licensed to Sell since 1985 . Altas Realty) over 7 years ago

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.

Posted by Jay Markanich, Home Inspector - servicing all Northern Virginia (Jay Markanich Real Estate Inspections, LLC) over 7 years ago

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!

Posted by TeamCHI - Complete Home Inspections, Inc., Home Inspectons - Nashville, TN area - 615.661.029 (Complete Home Inspections, Inc.) over 7 years ago

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

Posted by Jay Markanich, Home Inspector - servicing all Northern Virginia (Jay Markanich Real Estate Inspections, LLC) over 7 years ago

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.

Posted by Andrew Mooers | 207.532.6573, Northern Maine Real Estate-Aroostook County Broker (MOOERS REALTY) over 7 years ago

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.

Posted by Gabe Sanders, Stuart Florida Real Estate (Real Estate of Florida specializing in Martin County Residential Homes, Condos and Land Sales) over 7 years ago

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!

Posted by Jay Markanich, Home Inspector - servicing all Northern Virginia (Jay Markanich Real Estate Inspections, LLC) over 7 years ago

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

Posted by Michael Gendreau, Edina Realty (Edina Realty) over 7 years ago

Glad you could learn something Michael!

Posted by Jay Markanich, Home Inspector - servicing all Northern Virginia (Jay Markanich Real Estate Inspections, LLC) over 7 years ago

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

Posted by Scott Fogleman, Greater Good Group (New Home Team 804-573-9592) over 7 years ago

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

Posted by Jay Markanich, Home Inspector - servicing all Northern Virginia (Jay Markanich Real Estate Inspections, LLC) over 7 years ago

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