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Ghost Lines On Drywall - And How A Thermal Camera Sees Them

Ghost lines on drywall - and how a thermal camera sees them.

You've seen ghost lines, those shadowy lines on drywall.  You can see them in the walls and on the ceiling.

What are they?

They have been called ghost lines, drywall shadow lines, ghosting - but it doesn't matter what you call it.  Ghost lines happen.

But why?  What are they?

Ghost lines can be created by a variety of things - moisture, moving air, dust, soot, and particulates inside the walls or attic.  Sometimes nail or screw head spots can be seen as well.

Mostly what you see is insulation related.  When there are gaps between insulation, or it is loosely applied, falls down, or otherwise becomes separated from the drywall, air gets in.  This allows for a convective loop, or moving air, as it heats and cools.  It's the same principle as what moves air during a thunderstorm, when the wind blows.  Except inside a wall, or in an attic space, the moving air, or convective loop, is very small.

But the air still moves!  Heat seeks cold, so the air is almost always moving as there is not always a temperature equilibrium anywhere.  As temperatures change inside walls, ceilings, or attic spaces, air moves, and THERMAL TRANSMITTANCE happens through the drywall.

And those ghost lines appear!

 

Viewing the same location two different ways interesting things emerge.

The digital photo on the left clearly shows the ghost lines in the drywall.  I noticed them as I walked in and knew what Mighty Mo would see.

The thermal image on the right exactly mimics the lines on the left.  Except the thermal image is coupled with temperatures!  The ghost lines appear as dramatically cooler areas.  The coolest temperatures in the attic approach the air temperatures outdoors.

Thermal images lend a lot of information to the physics and thermal radiation that influences an indoor environment.  Until the arrival of thermal cameras to the home inspection scene (which I began using 13 years ago) we did not have this kind of evidence that accompanied what we suspected.

My recommendation:  thermal imaging gives a lot of definitive information about a property.  The house is the house.  The camera does not invent images.  They are based on temperatures, and can be described with a variety of palettes to give different kinds of information.  The information here is clear.  Insulation is a permanent thing in a house.  If it is done right, it is right forever.  If it is not done right, it is not right forever.  And the consequences of both of those things are forever.  It pays great dividends to do insulation right the first time!

 

 

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 12 commentsJay Markanich • November 24 2015 12:43AM

Comments

 Good Tuesday morning Jay. I have seen this happen quite often especially when people burn cheap candles.

Posted by TeamCHI - Complete Home Inspections, Inc., Home Inspectons - Nashville, TN area - 615.661.029 (Complete Home Inspections, Inc.) over 4 years ago

Interestingly, Michael, in this house there is a woodstove in an unfinished basement.  It was obviously used.  The heat pump unit is also located there, so I bet particulates have been carried through the walls and attic spaces as ducts throughout the house are serviced with heated air.

Posted by Jay Markanich, Home Inspector - servicing all Northern Virginia (Jay Markanich Real Estate Inspections, LLC) over 4 years ago

Crap!  I just noticed that half my post is gone!

Posted by Jay Markanich, Home Inspector - servicing all Northern Virginia (Jay Markanich Real Estate Inspections, LLC) over 4 years ago

There, I fixed it.

Posted by Jay Markanich, Home Inspector - servicing all Northern Virginia (Jay Markanich Real Estate Inspections, LLC) over 4 years ago

Good morning Jay. Mighty Mo leaves no stone unturned! Enjoy your day!

Posted by Wayne Martin, Real Estate Broker - Retired (Wayne M Martin) over 4 years ago

Wow, that is pretty dramatic.  I don't think I've ever noticed anything like that in the ceiling before, but now I'll look out for that.  I suppose also, that many paint over it so it's less noticeable.

Posted by Debbie Gartner, The Flooring Girl & Blog Stylist -Dynamo Marketers (The Flooring Girl) over 4 years ago

Jay Markanich Your diagnosis and explanation of this problem is appreciated. I have not seem this issue in all my decades of experience. Thanks!

Posted by Sandy Padula and Norm Padula, JD, GRI, Presence, Persistence & Perseverance (HomeSmart Realty West & Lend Smart Mortgage, Llc.) over 4 years ago

Good morning Jay,

As with any job it should be done correctly the first time.

Thank you for the explanation of the lines; I have seen them but never knew what they were.

Glad your were able to find the rest of the post.

Make yourself a great day.

Posted by Raymond E. Camp, Licensed Real Estate Salesperson Greater Rochester (Howard Hanna Real Estate Services) over 4 years ago

Jay, are you saying that air moving around the insulation is causing the ghost lines?  Is this moisture based or is it causing its own airflow environment on the outside of the drywall, which causes impurities in the air to stain the surface?  Interesting.

Posted by Stephen Weakley (Nationwide Mortgage Services) over 4 years ago

Ghost lines, ewwwww !   Thought those went away at Halloween Jay Markanich  

Posted by DEANNA EARLY - - ( NMLS # 268590 ), Highest Ranked Mortgage Loan Originator Virginia (American National Bank & Trust) over 4 years ago

I don't know why my answers to people are not printing!

Posted by Jay Markanich, Home Inspector - servicing all Northern Virginia (Jay Markanich Real Estate Inspections, LLC) over 4 years ago

Thanks Wayne.  Or ghost line!

Debbie - I see them all the time.  Especially country houses with particulates in the air from woodstoves.

I couldn't find it Raymond.  I had to rewrite it and publish it again!

Stephen - yes, condensation and air (and particulates) moving behind the drywall.  And particulates in the air on the room side of the drywall.

Deanna - they come out on Halloween!

 

Posted by Jay Markanich, Home Inspector - servicing all Northern Virginia (Jay Markanich Real Estate Inspections, LLC) over 4 years ago

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