Indoor stains appearing in streaks or dark lines or in rectangular areas in buildings traced to black or dark thermal tracking or ghosting:

What caused dark stain lines on walls or ceilings usually spaced at regular intervals, or dark rectangular stains on walls or ceilings? A combination of thermal tracking or ghosting and insulation voids may explain these indoor stains.

This article series describes & diagnoses the cause of various interior wall and ceiling stains and explains how to recognize thermal tracking, (also called ghosting or ghosting stains or thermal bridging stains), building air leaks, and building insulation defects.

Often these stains are mistaken for toxic indoor mold.

Why does Thermal Tracking or Ghosting Often Appear in Streaks or Lines?

Thermal tracking may mark the location of building framing members

In a conventionally-framed wood structure, wall and ceiling framing is typically spaced on 16" or 24" centers, and thermal tracking will tend to cause dust or soot to adhere to the interior surfaces at these locations because the R-value of the wall or ceiling is a bit less where the framing members are located than it is through the ceiling or wall cavity insulation.

You can see this phenomenon in our photograph of dark vertical lines along a wall in our page top photo, and just above, our ceiling stain photo shows lines corresponding to the location of ceiling joists.

[Click to enlarge any image]

Usually these parallel lines will appear on roughly 16-inch centers in a conventionally-framed building, or possibly on 24-inch centers where that framing method is used.

But thermal tracking or bridging stains may occur on different intervals depending on how the building was constructed, where air is moving, where air leaks are occurring, where there are gaps in building insulation, and wherever building surfaces are cooler or more moist.

Airborne dust particles, whether simply from normal house-dust or from a more-serious problem such as soot-producing heating equipment, sticks to the ceiling or wall surface more at those cooler, more-damp locations.

Thermal Tracking Stains as Lines, Streaks, or Spots in a Line

Ghosting or thermal tracking spots in parallel lines (photos above): black wall stains in a vertical striped pattern is particularly easy to identify on walls marking stud locations.

In less extreme cases of ghosting you may just see dark spots in relatively straight parallel lines marking the locations of studs and, in the case of the photograph above, ceiling joists.

In our photo below we see both the thermal tracking lines following wall studs and small dark round dots that mark drywall nails or screws.

Those spots are the locations of drywall nail or screw heads:

see WALL THERMAL TRACKING STAINS for some interesting examples of spots at drywall fasteners.

The reason thermal tracking tends to mark the location of building framing members is because the interior wall or ceiling surface will be cooler (during the heating season) where framing members (joists or studs) are located.

However as you can see in our photo below, do not assume that all thermal ghosting stains will track framing members. Air movement is reduced close to the ceiling-wall intersection, another location of ghosting stains.

[Click to enlarge any image]

But the insulating value of wood is pretty low (about R1 per inch) compared with fiberglass insulation or other insulating materials.

These points of increased building heat loss, caused by the presence of solid ceiling joists or wall studs separating building insulation are also called points of thermal bridging - points where there is more building heat loss than through the building insulation itself.

The sections of an interior wall or ceiling which are touching wood framing (inside the ceiling or wall cavity where a ceiling joist or wall stud was placed) will conduct heat to the outdoors faster than the "in between" sections of wall where insulation has been placed.

In sum, the wall or ceiling interior surface will be cooler where the framing is located than will be the spaces which are not touched by framing and which, perhaps, are insulated.

In sum, if you see black streaks up the building wall in a regular 16" or 24" pattern, particularly on cooler exterior walls but potentially anywhere, it may be thermal tracking.

Interior stains help diagnose building conditions: Since thermal tracking, or soot marking, or "thermal bridging" as a few folks call it usually tells us something about a lack of building insulation or about air leaks in buildings, we can use these marks or stains to learn important facts about a building.

Parallel dark lines that are not thermal tracking

The dark parallel wall stains above are probably just shadows. Details about this picture are found

at STAINS MISTAKEN for GHOSTING

This photo along with more photos of actual thermal tracking that was present in this home are also discussed

at THERMAL TRACKING GHOSTING FAQs

Causes of Dark Areas, or Rectangular Stains on Ceilings or Walls

Sooty or dark smudges or stains appearing near the ceiling On the inside of building exterior walls, especially in older homes whose interiors have not been re-painted or cleaned in some time.

Thermal tracking stains may appear at the top of the wall and extend onto the ceiling surface such as shown in this photograph.

Note those dark "stripes" extending along the ceiling and into the room?

These ceiling stains probably mark the location of ceiling joists (where the in-room ceiling surface temperature was kept a bit cooler since these locations in the ceiling cavity are occupied by a wood joist rather than by insulation).

See CEILING STAIN DIAGNOSIS for details of diagnosing stain patterns on building ceilings and on cathedral ceilings.

The dark rectangular stains on the kitchen ceiling shown in this reader-contributed photograph probably mark areas of insulation voids in the ceiling in the Australian home shown above.

Additional air leakage and convection currents occurring around recessed ceiling lights (pot lights) can increase the air movement into such ceilings and thus increase staining around the lights. [Thanks to Aussie reader T.D. for contributing this photo 1/3/2016]

Question: explain these large dark rectangles on our ceiling

The ceiling below attic has huge rectangles… fan in attic runs non stop. Not damp up there. Couldn’t find anything quite like this on your site. Father’s home. Not sure of next steps. - Ray S.

Moderator reply:

@Ray S,

That thermal tracking pattern, wide dark areas in ceiling joist bays separated by lighter lines marking ceiling joist locations, is the reverse of the more common pattern (light joist bays dark joist marks) and indicates - I am guessing - poor insulation in the ceiling.

The ceiling fan's use might be a factor in how quickly these big wide dark areas show up: by moving indoor air constantly over the ceiling more airborne dust comes into contact with the ceiling surface, giving more particles a chance to stick there.

We might confirm that if you observe that these stains are less or not even noticeable at all in other rooms on the same building floor but where there is no ceiling fan.

And we'll further confirm that theory if, when you inspect the attic, you see that the insulation, probably minimal, is nevertheless uniform over all of the ceilings.

Or, less common, we might find that insulation was just missing over some ceiling areas.

Watch out: In addition to considering adding insulation (after inspecting the attic for leaks, moisture, moldy drywall on the attic side of ceilings), you'd check to be sure that the dark deposits are only normal house dust - versus something more troublesome (sooty fireplace, scented candles, pets, poor housecleaning) or more-dangerous (improperly-operating oil or gas burners).

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Reader Q&A - also see RECOMMENDED ARTICLES & FAQs

On 2019-06-27 - by (mod) - painting the inside of a manufactured home for sale: problems

As you suspect a moisture problem that makes sense to have a thorough Home Inspection performed. The scope of that includes looking for leaks, moisture sources, moisture trap, and improper or blocked ventilation.

On 2019-06-27 by Lisa P

My husband and I are currently painting the inside of a friends manufactured home (1999) that they are selling

While working we noted some odd and concerning issue's. First several areas of the floor are soft and wavy, the walls in the 2 small bedrooms are literally warped horizontally when painting with a roller it was like going over speed bumps, in the master bedroom and bath there are signs of severe ghosting on walls and ceilings where we can actually see the complete outline of the frame. I personally believe there could be water or moisture damage.

Also it has taken at least 3 coats of premium paint with primer to cover even the walls with no visible sign of problems...the paint won't stick and this is an issue we have faced before where there was excess moisture in the walls.

I am not an expert by any means just going on past experience and have seen how water or moisture damage can get into a mobile or manufactured home undetected. I shared my thoughts and concerns with our friend and they were upset it seems with us for sharing and we only suggested looking into it.

are going to have an inspection done so can you give me suggestions on any particular type of inspection they should have done or even testing in the home for mold? Thank you from Washington State USA

On 2019-04-24 - by (mod) -

Perhaps with some photos of the stains and some information about the building country, city (*thus climate), age, type of construction (wood frame, insulated wall cavities0 etc. one can make a useful diagnosis.

Kitchen stains are also often related to deposits of soot or grease or smoke or even just the effects of moisture from cooking. As in the article above, such deposits can mark stud locations.

Watch out: some indoor soot sources can indicate dangerous conditions, such as soot produced from improperly adjusted or vented gas burners.

At THERMAL TRACKING BRIDGING GHOSTING - home https://inspectapedia.com/interiors/Thermal_Tracking.php

you will read more explanation of how and why thermal tracking type stains appear on walls. Please take a look there and let me know what questions remain.

On 2019-04-24 - by (mod) -

Perhaps with some photos of the stains and some information about the building country, city (*thus climate), age, type of construction (wood frame, insulated wall cavities0 etc. one can make a useful diagnosis.

Kitchen stains are also often related to deposits of soot or grease or smoke or even just the effects of moisture from cooking. As in the article above, such deposits can mark stud locations.

On 2019-04-24 by Jon Robertshaw

I have dark lines coming from above every plug socket and switch in the kitchen. They go up to the ceiling?

On 2018-06-13 - by (mod) -

Tany

Please see THERMAL TRACKING REMEDIES for details - at https://inspectapedia.com/interiors/Stain_Remove_Prevent.php -

and let me know if you have further questions.

On 2018-06-13 by Tany

How can I fix this? Who can check if it is an air leak? The roofer after seeing this confirmed that it is not a roof leak and suggested to get it painted. My concern is if there is an air leak, the stains will come back after sometime even if I paint that ceiling. What can I do to fix this? Thanks

On 2018-06-12 - by (mod) -

Tracking stains, associated with the combination of air leaks or voice and insulation and of course an indoor source of dust or switch or debris.

On 2018-06-11 by Tany

Hi, I have noticed this strange rectangular stain on my vaulted ceiling recently. I noticed these on a dry day ( no rain for few days). I believe the humidity inside the house was high as no AC was on for 10/15 days. Could this be thermal tracking? Also when I tried touching those area in a hot sunny day, I felt some points felt warm to touch then the rest of the ceiling. Same area I touched after a heavy rain, didn’t felt wet, but it didn’t felt warm that day. Any idea if it is due to missing or insufficient insulation on vaulted ceiling?

IMAGE LOST by older version of Clark Van Oyen’s Comments Box code - now fixed. Please re-post the image if you can. Sorry. Mod.

Reader question: will these stains in our home in Australia reappear after we clean and paint the stained surfaces?

I just read your article on Thermal Tracking, Bridging and Ghosting, and believe I may have this problem in my home.

I've had several builders around to look, and none of them have ever seen anything like it.

We've owned the house for 3 years now, and it seems to have started around winter last 2015 (I live in Australia so May/June). We don't have any open fireplaces or anything, just 2 reverse cycle air conditioners.

We recently cleaned out the filters on the living room air conditioner and it was filthy, so I was wondering if they may have been contributing to the problem. The house was poorly insulated, however I insulated the entire ceiling around June of 2015.

I recently cleaned some areas of the house with sugar soap and warm water, and the marks appear to come off, or just smudge around the wall/ceiling. Are you able to tell me what you think the problem might be, and the solutions to fixing it.

It seems to be slowly spreading to other areas of the house also. We were going to repaint the ceiling and walls, but I just want to know what this is and if it will come back again after I've repainted it. - T.D. 2016/01/03

Reply: Yes stains will recur until we correct the causes of thermal tracking or ghosting

Yes the chimney effect caused by the holes cut into a ceiling to mount pot lights (recessed ceiling lights) will increase the air movement around and up through each light, increasing deposits of building dust and soot thereon. But the root causes of thermal tracking remain:

1. Missing insulation - cooler areas will see more condensation of moisture on the wall or ceiling and thus will collect more airborne dust particles
2. Air leaks into a ceiling or wall will often increase dust deposition around the points of air leakage
3. Water leaks into a ceiling or wall or abnormally-high levels of moisture or condensation in such cavities.
4. Indoor soot and dust sources - including normal house dust sources - more dust sources = more rapid stain formation.
   
   We see this in buildings where people use scented candles, fireplaces, smoke, or where an oil burner is not properly maintained and is producing soot; pets, particularly big long-haired dogs who bring dust indoors also increase ghosting stain formation.
5. The indoor humidity level - more humid = more rapid dust deposition
6. THERMAL TRACKING REMEDIES for details

Watch out: I agree that you don't want to insulate over recessed lights if they are not rated for that application as doing so can cause overheating or even a fire; and changing all of the recessed lights to those rated for direct contact in an insulated ceiling (DCIC) so that they can be insulated over is a desirable improvement but not a cheap one.

But if we don't correct the causes of thermal tracking or ghosting it will return after cleaning and painting.

Reader follow-up:

I've been up in the roof today, and there are areas around the downlights that aren't insulated, but they've been left there so that we don't start a fire in the roof from the insulation coming into contact with a hot surface. I will have to look at some heat shields for the downlights so we can insulate the entire area.

Another interesting thing, which I think could be a definite problem is the exhaust fan duct from the kitchen goes into the ceiling but doesn't go any further, so any hot, fatty, humid air from Cooking goes into the ceiling but can't escape.

Could this be coming back down through the holes for the downlights and sticking to the ceiling causing these marks? The downlights do have a black sticky residue around them that spreads when touched with a wet cloth.

Reply:

Watch out: Venting a kitchen exhaust into a ceiling not to outside is unsafe and probably violates your local building codes. Over time the accumulation of grease can cause a building fire. I would stop using the fan entirely until it can be vented to the outdoors.

You typically need 3" of clear un insulated space around the ceiling pot lights but the light fixture should contain a label with the specific clearance distance for insulation; Those large dark rectangles on the ceiling suggest large cold areas of missing or incomplete insulation.

If it were my home I'd change over to DCIC rated lights that can be covered by insulation.

Insulation leaks & thermal bypass defects: We use thermal tracking marks on an area where insulation is visible to identify and correct air bypass leaks, thus saving energy or reducing home heating or air conditioning costs.

Details about air leaks in buildings are discussed

at AIR BYPASS LEAKS.

Building air leak testing is described

at BLOWER DOORS & AIR INFILTRATION

and at AIR LEAK DETECTION TOOLS.

Insulation adequacy: Clues that suggest Insulation adequacy can be picked up easily if the observer will use thermal tracking marks on larger areas of interior walls or ceilings to tell us areas of the building that are not insulated, or are not well insulated - areas where we should consider adding or improving insulation to save energy by reducing building heating or cooling costs.

See INSULATION INSPECTION & IMPROVEMENT for more information.

Usually soot marks, thermal bridging, or thermal tracking stains appear, if at all, in the building interior locations listed just below discussed in the remaining sections of this article.

On 2017-02-04 by Gail

Why is my insulation turning black and melting! Is this normal in a brand new home we are building

 

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Continue reading at THERMAL TRACKING REMEDIES or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see GHOSTING DARK STREAKS or LINES FAQs - questions & answers posted originally at this page

Or see these

Recommended Articles

• AIR MOVEMENT in BUILDINGS - When, where, how & why air moves in buildings.
• CEILING STAIN DIAGNOSIS
• MOLD APPEARANCE - STUFF THAT IS NOT MOLD
• STAINS on INDOOR SURFACES, PHOTO GUIDE
• THERMAL TRACKING BRIDGING GHOSTING - home
  • DEFINITION of THERMAL TRACKING
  • EIGHT INTERACTING FACTORS CAUSE GHOSTING
  • AIR VELOCITY & MOVEMENT PATTERNS
  • COMPOSITION of DARK GHOSTING STAIN PARTICLES
  • GHOSTING STAIN INSPECTION
  • GHOSTING DARK STREAKS or LINES: CAUSES
  • GHOSTING DARK RECTANGULAR STAINS: CAUSES
  • GHOSTING DARK STAINS from AIR LEAKS
  • GHOSTING DARK STAINS on INSULATION, AIR BYPASS LEAKS
  • GHOSTING STAINS on WALLS
  • STAINS CANDLES FIREPLACE WOODSTOVE
  • STAINS DIAGNOSE IAQ PROBLEMS
  • STAINS INDICATE SAFETY CONCERNS
  • STAINS MISTAKEN for GHOSTING
  • THERMAL TRACKING REMEDIES

Suggested citation for this web page

GHOSTING DARK STREAKS or LINES: CAUSES at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

Or see this

INDEX to RELATED ARTICLES: ARTICLE INDEX to BUILDING STAINS

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