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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.
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[Click to enlarge any image]
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. You can see this phenomenon in our ceiling stain photo above and in the wall stain photo at the top of this page.
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, and where ever building surfaces are cooler or more moist.
Ghosting or thermal tracking spots in parallel lines: This interior black wall stain pattern is particularly easy to identify on walls where in less extreme cases of ghosting you may just see dark spots in relatively straight parallel lines marking the locations of studs and joists: 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.
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.
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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]
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
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
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:
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.
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.
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.
Continue reading at GHOSTING DARK STAINS on INSULATION, AIR BYPASS LEAKS or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.
Or see CEILING STAIN DIAGNOSIS
Or see WALL THERMAL TRACKING STAINS - diagnosing ghosting stains on walls
Or see THERMAL TRACKING BRIDGING GHOSTING - home
Or see THERMAL TRACKING REMEDIES - curing ghosting stain problems in buildings
Or see AIR MOVEMENT in BUILDINGS - When, where, how & why air moves in buildings.
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Try the search box below or CONTACT US by email if you cannot find the answer you need at InspectApedia.
(Oct 2, 2014) Sam said:
Wow, what a great resource, thank you so much for all the info! Question: Garage ceiling has this tracking at all the drywall seams. I can see that the ceiling was insulated. Dark spots exactly correspond with the 12" joint compound finishing knife. Could it be that the compound was simply not sealed properly when it was painted? Also, could exhaust from cars cause this-it's nowhere else in the house.
Thanks, I love this site!
I don't think so. More likely the joints are over studs, pipes, or cooler surfaces that pick up a bit more moisture and thus particle deposits thus stains.
Yes car exhaust could be a particle source, also a moisture source. And if the car is burning oil and is left running for some time in the garage these effects would be increased.
Watch out: for potentially fatal carbon monoxide hazards if car exhaust can enter the home or accumulate in the garage.
(Jan 17, 2012) John Dabbs said:
A friend has black deposits appearing evenly on vertical surfaces at the top of an internal lounge wall, just under the coving. The wall-hung pictures also have severe dirt 'shadows'. The appearance is similar to that I experienced when I had a de-ioniser in use in my bedroom, but there is none in the friend's lounge but there is a tv and modern wall-hung logfire-effect unit. Heating is by conventional hotwater radiators. The house is right on the sea front (at Bude) and fully exposed to off-sea winds. Could the cause be thermopherosis? Caused by deionisation from sea spray? Or what? And what might the solution be? No nearby pollution source that I can identify.
John, if by "appearing evenly" you mean at even spaces or intervals such as marking the intervals of building framing members, that would be a classic diagnostic clue indicating thermal tracking.
And yes, using a "de-ioniser" (more likely it was an ionizer - a device that puts an electrical charge on dust particles, causing them to plate out on wall and other building surfaces) can contribute to soot and thermal dust tracking stains on building walls and ceilings.
I'm not sure of the role that off-sea winds would play in thermal tracking - it depends ... for example on the effect of winds on building heat loss. Sea spray itself sounds an unlikely cause to me as I don't imagine much sea spray enters the building interior.
Even common house dust will be enough of a particle source to explain thermal tracking in buildings, but where there are additional dust or particle sources the effects will appear more rapidly and at more extreme levels. Examples include an oil burner that is not working properly, producing soot; use of candles, scented candles, woodstoves, fireplaces, or even burning cooking materials. Pets can also be contributors.
The solution to thermal tracking includes:
- identify and remove sources of high levels interior dust or particulate debris as much as possible
- identify locations of building air leaks and heat losses and correct them
- add insulation, particularly where there are voids
- monitor and correct high levels of interior moisture
Many thanks indeed, Dan, for your comments. Perhaps I should have said that the staining is "uniformly" spread ie a consistent level along the upper perimeter of the room, graduating in intensity as the ceiling is approached. The wall construction is, I believe, solid masonry (I'll check that), and the effect is apparent on all walls whether internal or not. One wall - facing the sea - has a large double-glazed sliding patio door and a "soot" film appears on this after only a few days after cleaning.
Yes, I should have referred to an ioniser - I apologise! It was because of the similarity of this problem to my previous experience with one of these that I was wondering if this was due to an ionising effect somehow. Hence I was wondering if excessive sea spray could cause ionisation? Clutching at straws? The household has a cat, but it's a large, open house. The room is clean with few furniture pieces, all modern, with a fitted carpet. There are a few nearby properties, all as far as I know with natural gas heating. Completely residential area, and I can't identify an probable sources of dirt/soot particles, but I'll have another look around. No woodfires, candles or oil burners. Two of the walls have hot water radiators fixed to them, but the staining is at the same level on a third wall with no heating fixed to it.
Any further thoughts?
(Feb 26, 2012) Jerry said:
How do I clean painted wall from streaking
Jerry, identify the cause, fix that source first; then wash and seal and paint the walls. You might want to use a lacquer primer sealer for best results.
Apr 7, 2012) sue white said:
we have a friend with a house that has ghosting at the 2nd floor ceiling and top 1-2' of wall where it meets the ceiling; the nails are also popping at this ceiling/wall juncture. the house is entirely electric with exception of a gas fired stove in the lower level of the split level home.
do you think the ghosting is due to a malfunction with the stove or some other issue? thank you
Not likely - but
Watch out: a gas cook stove that is making visible soot is not working properly and is unsafe, risking fatal carbon monoxide poisoning.
(Feb 20, 2014) Anonymous said:
how does one get ride of thermal tracking.
Good question, Anon.
First, the actual black sooty marks can be removed by cleaning washable surfaces; typically we use a non-sudsing detergent. On carpets the carpet would have to be shampooed.
But to complete the "get rid of thermal tracking" process we need to look at what is causing the soot or dust marking and address the underlying causes (which are discussed in this article series).
As some examples:
- look for and fix any extra sources of dust or soot like a poorly-tuned oil burner, use of a fireplace, scented candles, smoking
- check the indoor humidity level and if it's too high we need to fix moisture sources or dehumidify the building - see HUMIDITY LEVEL TARGETS
- See THERMAL TRACKING REMEDIES for complete details
(Feb 24, 2014) Sarah said:
My husband and I just notified a stain on the ceiling that wasn't there 7 months ago when we moved in. It's a light pinkish tan stain on a textured ceiling. It is about 3 ft shy of an air vent in our breakfast nook. It does look like a type of moisture stain but nothing similar to your mold patterns you've posted pictures of on the website. This is a ceiling below our guest bath. Any ideas?
Sarah, I'd have to see some sharp photos (you can use our CONTACT link if you like);
Generally the location and size of a ceiling stain will suggest something about possible sources, e.g. a possible leak from above.
4/2/14 Kathy said:
we have been experiencing the same we moved to a house 2 yrs ago and especially during the winter it seems to get darker marks. this winter we noticed it a lot more. I have pictures but unsure how to load them here. we see the ceiling marks by the beams as well as the corner marks or above the heat. should we be concerned?
You can use the CONTACT link at page bottom to send us photos. I'll take a look.
(Oct 7, 2014) Brennan said:
Have you ever seen this in carpet in the middle of a room (not near the baseboards). I received a moisture meter to check some ceiling stains to see if they were active or inactive after the former owner replaced the roof. I was using the moisture meter to check the basement- all surfaces. I found some areas in the basement carpet where the moisture meter was high but dry to the touch. I run a humidifier in that room and it doesn't work very hard to maintain 45-50 rh%
It has a 'line' type stain. A bit darkened (carpet is grey, so this is darkish grey), but not like the other areas where there is actual infiltration soiling (I have seen it is one room near the baseboards but is completely dry). My home is old, so of course it has air leaks.
The former owners had a couch over this area, so I thought it was due to that. Adjacent staining is yellow coloring and also shows moisture in the meter. So moisture and a line/ghosting in carpet. The carpet is gross anyway, so I thought about peeling it back to see if there is a crack in the slab (60+ yr old house). A contractor friend, without seeing it, said it was radon gas escaping. That seemed like a stretch, since Radon is colorless. I think though, perhaps he meant, air is feeding through the crack and depositing soil on the carpet.
If I do find a crack- should is seal it with concrete/caulk and re-carpet and be vigilant about dehumidification?
A couple of points to consider:
Most moisture meters, if we exclude thermal imaging, rely on measuring differences in electrical resistance to detect moisture. But other contaminants or materials can also decrease resistance in an area of building material. So not every reading variation is necessarily truly detecting moisture. Some attention, particularly looking for possible moisture sources, are key.
Both pin type moisture meters (Delmhorst for example) and electronic moisture meters (such as some Tramex meters) can be fooled by metal nearby: pipes, foil faced insulation, wiring.
Second: no moisture meter, nor thermal imaging device, can detect old leaks that have since dried, even though the leak might have initiated a building problem with rot, insect damage, or mold contamination. This is why we argue that reliance on meters and imaging alone for water or mold detection are unreliable. But the instruments are indeed useful, in thoghtful hands. And neat too.
(Oct 9, 2014) Brennan said:
Thanks for your comment. One thought (using my science background) was that the moisture meter gives a high reading on what looks like an old dog urine stain (former owner had dog). I had the thought that these left over salts and ions from the urine might act as a weak conductor and activate the moisture meter. On the internet, it seems that carpet companies use moisture meters to find hidden pet stains, because the salt from the urine can draw moisture from the air (or even just the natural evaporation of the concrete slab). So, thanks for your help. I tend to over-think things. I agree, it is a neat tool.
(Oct 9, 2014) (mod) said:
Interesting Brennan, and thoughtful. I agree with the salts / ions theory for both of the reasons you offer.
It's not over-thinking. The more we understand the better we can find and fix or prevent aggravations. Thanks.
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