HVAC Ducts Should Not Have Holes Inside The Walls

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

HVAC duct planning is a difficult enough of a science, but some installations are designed to fail as 

HVAC ducts should not have holes inside the walls.

Why do I say planning duct work is a difficult science?

Because their job is to balance air flow and the indoor temperature, and that ain't easy!  Many, many factors go into designing the HVAC system for a house - sizes of rooms, open spaces, numbers of windows and doors, cubic this and that, and on and on.  Air has to evenly come and go.  It really is a design best done with computer programs.

Older homes had heating systems that blew air around with small, metal ducts.  Metal ducts are famously leaky

Someone got the idea to wrap some joints and such with tape - the infamous duct tape.  And it worked, basically, but only until the tape dried out and the leaking began again.

Now HVAC science uses a combination of metal ducts and flexible ducts.  Flexible ducts are nothing more than huge slinkies with plastic wrapped around them.  Some are insulated.  They can be extended and fitted and wrapped around things to send air where ever.  But it all must be tight!  No leaks! 

The latest method of sealing seams and joints in metal duct work is a latex paste.

It is a thick material, like painting with peanut butter.  When it dries it seals cracks such that when the ducts expand and contract with temperature changes it can move to.  It is working well.  You can see it in this photo.

But it doesn't work so well when the plumber cuts through the duct to run a drain line!  That drain line passes COMPLETELY through the  metal duct!


It would forever have been a duct that weakly transferred air to many HVAC registers.  Those rooms would never have been properly conditioned.  The HVAC company would have been called and called to measure and test and nobody would have been able to figure out why those registers did not blow much air.

The reason, of course, is that the duct would have been blowing its air


It might never have occurred to anyone to call a thermographer (who are all really cute) to see if there might be leaking inside the wall anywhere.

This is what leaky metal ducts look like inside a wall traveling from basement to upper level to condition the bedrooms upstairs.  That warm air looks orange and yellow in the thermal image.  The inside of that wall is comfy warm!  The bedrooms in that house weren't so comfy.

The hole in the metal duct above would have leaked terribly!  It would have lost a large portion of its air pressure.  And forever!

Had we not done a pre-drywall inspection the interesting plumbing arrangement above would not have been handled and drywall would have gone up.  The supervisor didn't see it or didn't care.  The county approved the HVAC and didn't see it or didn't care.


My recommendation:  it's an exceptional idea to have a pre-drywall inspection done on new construction.  You never ever know what the home inspector might come up with!  The home inspector is an objective voice and had an objective eye.  What he finds on the inspection won't simply be blowin' in the wind.  He'll note anything important!  And if he's a really cute thermographer, well, even better!



Posted by

Jay Markanich Real Estate Inspections, LLC  

Based in Bristow, serving all of Northern Virginia.

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



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Sally K. & David L. Hanson
EXP Realty 414-525-0563 - Brookfield, WI
WI Realtors - Luxury - Divorce

Who knew,...and you think it is cold there...hmmm...all things relative...the bedrooms could double for chest freezers here !

Nov 11, 2014 09:20 PM #1
Jay Markanich
Jay Markanich Real Estate Inspections, LLC - Bristow, VA
Home Inspector - servicing all Northern Virginia

Temperature extremes in different rooms happen S&D!  Poor HVAC, poor insulation, or both!

Nov 11, 2014 09:31 PM #2
Dorie Dillard CRS GRI ABR
Coldwell Banker United Realtors® ~ 512.750.6899 - Austin, TX
Serving Buyers & Sellers in NW Austin Real Estate

Good morning Jay,

A pre-drywall inspection is a must on a new home. The home inspector is a qualified objective eye and can voice legitimate concerns. Buyers need to make sure this is done to assure them their home is energy efficient

Nov 11, 2014 10:01 PM #3
James Quarello
JRV Home Inspection Services, LLC - Wallingford, CT
Connecticut Home Inspector

I have seen pipes sent through ducts, but that one takes the cake! 

Nov 11, 2014 10:17 PM #4
Raymond E. Camp
Howard Hanna Real Estate Services - Ontario, NY
Licensed Real Estate Salesperson Greater Rochester

Good morning Jay,

It would be alright for me as I like it cool at night; just think if the plumbing ran through there as well!

Make yourself a great day.

Nov 11, 2014 10:38 PM #5
Fred Hernden, CMI
Superior Home Inspections - Greater Albuquerque Area - Albuquerque, NM
Albuquerque area Master Inspector

Yet another reason to get a pre-drywall inspection!! Love the drain line through the metal duct.... is that blatant or what? 

Installer to Superintendant: Yeah, I got dat dere drain line done, I took a short cut and saved you $15!

Superintendant: Great, as long as it's done!

Nov 11, 2014 10:58 PM #6
Charles Buell
Charles Buell Inspections Inc. - Seattle, WA
Seattle Home Inspector

The plumber must have left his small duct hatchet at home.

Nov 12, 2014 12:27 AM #7
Jay Markanich
Jay Markanich Real Estate Inspections, LLC - Bristow, VA
Home Inspector - servicing all Northern Virginia

I think so too Dorie.  An absolute necessity.

And it's one nice looking cake too Jim.  Yellow cake with chocolate icing?

I have seen that too Raymond!  These plumbers are good!

Fred - particularly if it's 3pm.

Charlie - look at the cut out.  This was done with a metal duct-cutting tool.

Nov 12, 2014 01:19 AM #8
Tom White
Franklin Homes Realty LLC (615) 495-0752 or www.FranklinHomesRealty.com - Franklin, TN
Franklin Homes Realty LLC, Franklin TN

Unbelievable, really. Without the pre-inspection that homeowner would have been paying forever to heat the inside of his walls!

Nov 12, 2014 06:02 AM #9
Jay Markanich
Jay Markanich Real Estate Inspections, LLC - Bristow, VA
Home Inspector - servicing all Northern Virginia

That is exactly right Tom.  And would they have ever figured it out?

Nov 12, 2014 09:55 AM #10
James Dray
Fathom Realty AR LLC - Bentonville, AR
Exceptional Agents, Outstanding Results

Those county and city inspectors who don't catch those things should be called on it.  There needs to be some sort of checks and balances with the State to either train or get rid of those people who don't follow the rules.

Nov 12, 2014 07:06 PM #11
Jay Markanich
Jay Markanich Real Estate Inspections, LLC - Bristow, VA
Home Inspector - servicing all Northern Virginia

Good luck with that James.

Once I said on an inspection that a natural gas water heater was put into a house with a propane fuel source.  This is incorrect and dangerous.  The seller said that the county approved it.  I was berated by all parties as an idiot.

A month later lots of people came for a visit and the water heater was over used.  It exploded.  I was not surprised.

When I called the county to tell them they simply said they can't be responsible to see everything.  There you go...

Nov 12, 2014 08:09 PM #12
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