InspectAPedia®

Photograph of  thermal tracking or soot tracking - cool surface, moisture condenses, soot is deposited - Daniel Friedman 02-12-16 Thermal Tracking: How to Diagnose Indoor Wall or Ceiling Ghosting Stains

  • THERMAL TRACKING BRIDGING GHOSTING - CONTENTS: Ghosting Marks: what causes those dark stains on building interior walls & ceilings? Photos & text identify thermal tracking, thermal bridging, air bypass leaks, insulation defects and air movement in buildings. Thermal tracking stains or dark thermal ghosting stains (also called thermal telegraphing stains) indoors indicate building air movement, air leaks, and points of heat loss which increase home heating or cooling cost. How to recognize poorly insulated building walls or ceilings and how to pinpoint building air leaks. A photo-guide to common indoor ceiling and wall stains and what they mean. Why & how thermal tracking and ghosting stains could indicate very dangerous carbon monoxide hazards in a building. Soot from natural gas, LP gas, or oil burners - sooting gas appliances are dangerous. Thermal tracking marks can indicate thermal bridging: locations of building heat loss. Definition of THERMOPHORESIS
  • POST a QUESTION or READ FAQs about indoor stains and thermal tracking or ghosting on walls and ceilings
  • REFERENCES
InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers, products, or services discussed at this website.

Indoor stains in buildings traced to black or dark thermal tracking or ghosting lines:

Building Air Leaks & Heat Loss Points. This article 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.



Green links show where you are. © Copyright 2017 InspectApedia.com, All Rights Reserved.

What are Thermal Tracking, Ghosting, Sooting, Thermophoresis, Electrostatic Deposition, Plating-Out Stains

Vertical black stripe stains on walls are most likely thermal tracking or ghosting (C) InspectApedia

[Click to enlarge any image]

Article Series Contents

What is Thermal Tracking & Why does Thermal Tracking or Thermal Staining Occur Indoors?

Photograph of thermal tracking on an indoor wall

What is thermal tracking or ghosting and what causes it?

Thermal tracking or "soot tracking" such as shown in the photo at left and also in the photograph at the top of this page may be found wherever moisture condenses on cool building surfaces.

Warm moisture-laden air touches the cooler surface of a building wall or ceiling, giving up some of its moisture to the surface as condensation.

See DEW POINT TABLE - CONDENSATION POINT GUIDE for details.

That makes some areas on an indoor surface slightly more damp than others.

As air moves by natural convection through the building, it typically flows up walls and across ceilings.

Airborne debris in the air, particularly soot such as that left by airborne house dust, by a heating system that needs service or by burning candles (scented candles may be more of an IAQ issue), or by cigarette smoking, adheres more to the damp surfaces than to others, leaving black marks or "tracks."

Black thermal tracking stains may appear on interior walls and ceilings, not just on cool exterior building walls. It is also possible that an interior partition wall may be conducting heat out of the building through convective loop heat losses as well.
See CONVECTIVE LOOPS & THERMAL BYPASS LEAKS.

While most people don't use the terms thermal tracking or ghosting with great precision, it is useful to understand how particular stain patterns are laid down in a building. Understanding the location, shape, size, and intensity of a stain on a building wall or ceiling can help us understand how a building works, its energy efficiency, and the quality of its indoor air.

To track down and fix thermal tracking stains you will need to fix air leaks and provide insulation where it's missing or inadequate.

However beware that on occasion the leaks and moisture in a building that contribute to thermal tracking may have created a mold problem somewhere else than in the black thermal tracking or soot marks you see on walls and ceilings.

MOLD / ENVIRONMENTAL EXPERT, HIRE ? provides assistance in deciding if you should hire a mold investigator.

Because some clients have on occasion sent samples to our mold test lab that really should not have been collected, much less looked-at, we recommend that you review the photographs in these articles to see if the black stains you see are something other than mold. When investigating a building for a mold problem, you can save mold test costs by learning how to recognize Stuff that is Not Mold or is only Harmless Mold but may be mistaken for more serious contamination - save your money

Eight Interacting Factors Determine When & Where Stains Appear in buildings

Ceiling stains at recessed lights © Daniel Friedman

[Click to enlarge any image]

Thermal tracking or "ghosting" is the deposition of house dust and debris onto walls and ceilings in patterns caused by a combination of air movement, interior moisture, and in some cases, a source of high levels of particles. The rate of particle deposition that ultimately forms these dark indoor stains depends on several variables including the following factors that I list alphabetically rather than in importance for the typical homeowner. I include links to related articles that go into greater depth but I suggest wading through this one in its entirety first.

Conflicting variables are at work in the deposition of soot and debris on building surfaces. Here are some examples:

Let's look briefly at thermal tracking's causes, arranged alphabetically rather than in order of impact on the formation of indoor stains on ceilings & walls, or thermal tracking / ghosting:

Eight Factors that Determine the Level of Thermal Tracking or Dust Particle Deposition on Ceilings & Walls

  1. Air velocity: the speed of air movement over a building surface affects the rate of deposition of particles on the surface. Faster air movement brings more particles in contact with the surface where depending on other factors, they may plate out or stick.
    Air movement in buildings occurs at different velocities in different areas even within the same room, depending on the location of incoming air sources (such as an air conditioning or warm air heating vent) and on sources of heat that cause convection currents in the room or even inside building exterior walls or interior partition walls. This variation may explain why we see dark thermal tracking stains above heating radiators and baseboards even though those are not forced-air heating systems.
    See
    AIR VELOCITY & MOVEMENT PATTERNS in this article (below) for details about this factor

    For help in studying this parameter
    See AIR FLOW MEASUREMENT CFM
    and also
    See AIR MOVEMENT in BUILDINGS
  2. Carbon Dioxide CO2 level: in public buildings or offices or your well-attended church or synagogue where the number of occupants might increase the indoor CO2 near 2000 ppm, increased carbon dioxide levels combined with high indoor moisture can encourage the deposit of white deposits of calcium bicarbonate. This is a particular concern in museums or at the Sistine Chapel, as Grabon (2015) explains, noting that for the Sistene Chapel the HVAC system has been designed to keep the CO2 below 800ppm. You won't see these deposits in a normal residential structure.
    See this related article:
    ARTWORK MOLD CONTAMINATION
    and also
    see TYPICAL CO2 LEVELS
  3. Ceiling or Wall temperature: the interior surface temperature and its variation from the temperature of room air determines if condensation will occur on those surfaces at all.

    Warm air carrying moisture will increase condensation on the cooler surfaces. If you can keep the wall surface temperature always 18F or 10C above the dew point temperature, there will be no condensation on your walls. You can do this by managing room temperature or by managing the RH of the air in the room, or both.
  4. Dew point temperature: when the ceiling or wall surface temperature is below the dew point temperature moisture will condense on the surface. The moisture collecting on those surfaces then causes more airborne particles to adhere. Keeping a wall temperature close to the nearby air temperature minimizes particle deposition. The dew point temperature is the air temperature at which the air is saturated: it can't hold any more water.
    See DEW POINT TABLE - CONDENSATION POINT GUIDE

    We exlore define dew point temperature and relative humidity (RH) and we explain the relationship of temperature and RH in a separate article at DEW POINT CALCULATION for WALLS
  5. Non-Particulate airborne pollutants: other non-particulate pollutants also affect building surfaces, particularly sulfur dioxide (SO2), as in interiors where the RH is high, the moisture in air combining with SO2 can actually form sulphuric acid that in a museum or where there are frescoes or other important surfaces, the acid may attack these materials.
  6. Particle composition & level in the air: soot, burning candles, fireplaces, pets, increase the particle level. In public buildings particles also enter the buidling from people, not just their pets, but also on shoes, clothing, carried items.

    For protected areas such as museums and indoor frescoes, Grabon (2015) cites an HVAC design level that keeps the indoor dust concentrations (particle size range ParticulateMatter PM 2.5 microns) below 0.003 µg/ft3 (0.1 µg/m3). That's a dust control level enormously more stringent than you'd seek for a normal residential space. For example the US EPA's 24-hour fine particulate standard is 35.0 µg/m3 - the same particle level as the output air from some of the best carpet vacuums cited by the Carpet and Rug Institute (CRI).
    See
    AIRBORNE PARTICLE COMPOSITION in this article (below) for details about this factor

    Also see CAUSES of VARIATION in AIRBORNE PARTICLE LEVELS
  7. Relative Humidity: Rh as a Factor in the Development of Indoor Stains on Building Surfaces: If indoor humidity is excessive (say regularly over 50 or 55% RH) we may be encouraging both staining from soot and house-dust deposition as well as mold growth in a building. Also we may be inviting excessive levels of dust mite activity which in turn increases the level of allergens in the building.

    That is because higher humidity indoors provides more moisture to condense on cooler building surfaces whenever the temperature of a building surface reaches the dew point. Stated another way, if a building has low indoor humidity, the amount of moisture available to condense on cool surfaces is less, so the rate of thermal tracking or soot deposition on those surfaces is less - at least due to this factor.

    See DEW POINT TABLE - CONDENSATION POINT GUIDE for details about the dew point and how to measure or calculate it for a building area or surface.

    Also see HUMIDITY CONTROL TO PREVENT MOLD

  8. Wall surface temperature and its variation from the temperature of room air: warm air carrying moisture will increase condensation on the cooler surfaces. If you can keep the wall surface temperature always 18F or 10C above the dew point temperature, there will be no condensation on your walls. You can do this by managing room temperature or by managing the RH of the air in the room, or both.

Even if the building humidity levels are low, high levels of indoor dust and debris can still lead to indoor stains and thermal tracking marks. Other factors that may be at play include electrostatic attraction or thermophoresis, discussed later in this article.

Air Velocity & Patterns vs the Level of Thermal Tracking or Dust Particle Deposition on Ceilings & Walls

Air velocity & air movement patterns: the speed of air movement over a building surface affects the rate of deposition of particles on the surface. Faster air movement brings more particles in contact with the surface where depending on other factors, they may plate out or stick.
Air movement in buildings occurs at different velocities in different areas even within the same room, depending on the location of incoming air sources (such as an air conditioning or warm air heating vent) and on sources of heat that cause convection currents in the room or even inside building exterior walls or interior partition walls. This variation may explain why we see dark thermal tracking stains above heating radiators and baseboards even though those are not forced-air heating systems.

For more help also
See AIR FLOW MEASUREMENT CFM
and
See AIR MOVEMENT in BUILDINGS

Air Movement Patterns as Factors in the Development of Indoor Stains on Building Surfaces

Specific and non-uniform moment of building air can lead to uneven soot or house dust deposition on building surfaces, and thus will cause stains and dark areas that are non-uniform . Surfaces across which more building air moves are exposed to a greater volume of air and thus a greater volume of dust particles.

Electrostatic deposition,  plating out and thermophoresis of ultra-fine airborne particulate debris also explains black stains, sooting, or ghosting, as has been pointed out by Roger Hankey and Joe Lstiburek and others.

Photograph of thermal tracking on an indoor wall

Electrostatic deposition refers to the sticking of particles to a surface due to a difference in electrical charge between the particle and the surface.

We often observe heavy electrostatic deposition of indoor dust and debris on building walls, ceilings, and other surfaces (most visibly on walls and ceilings) in homes where an ion generator is being used in the belief that it is "purifying" indoor air.

A friend in Rhinebeck, NY cranked up her indoor air ionizer to reduce the level of dog dust in her home - she boards as many as 15 dogs at a time in her home.

Indeed over just a few months we observed empirically that there was an increase in the rate of sooting on indoor painted walls and ceilings. Particles were probably sticking to other surfaces as well, but they were less visible.

Watch out: excessive use of indoor air ionizers, especially improperly adjusted, can produce harmful levels of ozone indoors.
See OZONE MOLD / ODOR TREATMENT WARNINGS.

Brownian motion, or pedesis, describes the random movement of particles, in this case airborne particles, perhaps impelled by energy from heat, light, or ambient air current, possibly plating out by impact collision with building surfaces.

Thermophoresis is a term used by some IH professionals to explain the combined action of particle impact, moisture, and adhesion to surfaces, and is explained below at Thermophoresis as a Factor in ... Indoor Stains

But unlike common thermal tracking, particles that are deposited on building surfaces by electrostatic deposition, brownian motion, or thermophoresis may be expected to occur without the presence of uneven surface moisture, temperature, and thus classic thermal tracking features.

Filtration and Thermal Tracking or Ghosting on Carpeting and Possibly other Fabrics such as wall curtains can indeed explain dark stains on carpeting under doors and at room perimeters where there may be air leaks.

Lstiburek offers a compelling explanation that airborne dust and debris (of all particle sizes) is filtered out by the carpeting or other fabric surface over which air may be passing. So a difference in air pressure between rooms (someone is running an exhaust fan for example), or air leaks at the perimeter of a floor (construction is leaky and cold air is rising from a crawl area or from outdoors into the occupied space of an upper floor,for example) indeed can deposit dark black stains on carpeting.

Airborne Particle Composition in Black Stains Found in Thermal Tracking or Electrostatic Deposition

Vertical black stripe stains on walls are most likely thermal tracking or ghosting (C) InspectApedia

Our photo of black vertical stripes on walls of a home was contributed by an InspectApedia reader who asked what they were. Because the lines so neatly map wall stud spacing these are almost certainly thermal tracking or ghosting marks explained in this article.

But what makes up the dark stains? Pretty much regardless of the variouis mechanisms that cause airborne particles to deposit on ceiligns or walls where they form dark stains or "sooting" or "ghosting" on interior building surfaces, the actual particles that can be expected to make up the stain include the following:

What particles are unlikely to make up the black stains associated with thermal tracking or ghosting?

In our forensic lab we have examined surface particles from literally thousands of building samples, including soot stains from dark or dirty surfaces, leading to the opinion about thermal tracking and plating particle makeup.

Other indoor particles that may be common in buildings and are cited by some other writers including some building scientists (Lstiburek) are less likely to be found in the black or dark indoor surface stains we describe here, for the reasons we list below. Some of these less-likely sometimes-airborne particles that have been posed as candidates for participating in the thermal tracking or ghosting festival include:

Brownian motion? As building scientist Joe Lstiburek points out, brownian motion also can cause particle adhesion to indoor building surfaces by the simple mechanism of mechanical impact of the particle with a building surface. But particles that remain airborne in Brownian motion are ultra small and thus less likely to include most of the particles listed above.

Visual Inspection by an Expert can Usually Sort Out the Causes of Building Stains

Conceptually, the deposition of dust, soot, or debris on building surfaces out of moving air in buildings (as opposed to caused by animals or people touching surfaces) is a complex linear equation that is weighing different and conflicting factors.

Luckily, the visual inspection of the stained areas, combined with inspection of the building for moisture problems, insulation and ventilation problems, or for soot and debris sources, can normally identify the dominant effect and can with confidence conclude the cause and thus suggest the cure for these stains.

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

Photograph of thermal tracking on an indoor wall

Typically these dark lines mark the cooler wall or ceiling surface areas where studs or joists are present; you may also see dark spots in lines marking drywall nails or screws for the same reason.

Details about the formation of ghosting lines on walls or ceilings have been moved to GHOSTING DARK STREAKS or LINES: CAUSES

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 (left).

This interior black wall stain pattern is particularly easy to identify on walls - see WALL THERMAL TRACKING STAINS.

 

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

Dark rectangular stains on ceilings showing missing insulation and ghosting or thermophoresis stains (C) InspectApedia TD

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

Details about rectangular stains on walls & ceilings have been moved to GHOSTING DARK RECTANGULAR STAINS: CAUSES

Role of Building Air Leaks in Thermal Tracking Marks at Interior Ceilings or Walls

Photograph of thermal tracking on an indoor wall

This discussion has moved to GHOSTING DARK STAINS from AIR LEAKS

 

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

Black Stains on Insulation: Air Bypass Leaks

Air bypass leak stains on building insulation © Daniel Friedman

This discussion has moved to GHOSTING DARK STAINS on INSULATION, AIR BYPASS LEAKS

How to Use Indoor Stains Like Thermal Tracking to Diagnose Building Air Leaks, Insulation Defects, and Indoor Air Quality Problems

This discussion has moved to STAINS DIAGNOSE IAQ PROBLEMS

More Indoor Stains Identified as Ghosting or Bridging

A careful examination of the location of indoor stains permits the observer to use thermal tracking or soot marks on building walls or ceilings as an indicator of possible excessive (seasonal) interior moisture or other potential indoor air quality concerns.

Dark stains on building interior walls may appear in other patterns and could be from other causes - we provide photographs, description, diagnosis, and advice for many of these indoor stains in this article series. Let's start with another example of THERMAL TRACKING BRIDGING GHOSTING so that we an distinguish these stains from others listed below.

Reader Question: pictures from our living room.

... these stains are getting worse ... my husband does notice that insulation seems to need work.... Everyone keeps saying it cant be healthy ... I'm worried - K.C. 4/4/2014

Reply: how to recognize thermal tracking or ghosting stains in buildings

Thermal tracking or ghosting stains on building ceilings (C) InspectApedia KC

There is no doubt that we are looking at thermal tracking or "ghosting" - deposits of dust and soot on cooler, more humid areas of ceilings in your home.

These are not themselves a particular health concern but the conditions that cause thermal tracking, if they involve high indoor moisture levels, particularly if that moisture comes from a damp or wet basement or crawl space, could be a subtle clue that there is a hidden mold problem in the building.

Watch out: if the building soot source that is providing material for the black ghosting stains in your photos were an improperly-operating heating system or gas fired appliance dangerous conditions could be present such as carbon monoxide.

In our separate article on recognizing indoor stain types IAQ DIAGNOSIS via THERMAL TRACKING STAINS I discuss all of your photos in more detail.

We explain this phenomenon beginning at the start of this article and we offer some remedies
at THERMAL TRACKING REMEDIES.

Stains that are NOT Thermal Tracking, Bridging or Ghosting

This discussion has moved to STAINS MISTAKEN for GHOSTING

Photograph of dirt on a ceiling at an HVAC supply register

...


Continue reading at GHOSTING DARK STREAKS or LINES: CAUSES or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.

Or see THERMAL TRACKING GHOSTING FAQs - diagnostic questions & answers about indoor stains traced to thermal tracking or bridging

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

Or see WALL THERMAL TRACKING STAINS - diagnosing ghosting stains on walls

Suggested citation for this web page

THERMAL TRACKING BRIDGING GHOSTING at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

INDEX to RELATED ARTICLES: ARTICLE INDEX to BUILDING STAINS

Or use the SEARCH BOX found below to Ask a Question or Search InspectApedia


...

Frequently Asked Questions (FAQs)

Click to Show or Hide FAQs

Ask a Question or Search InspectApedia

Use the "Click to Show or Hide FAQs" link just above to see recently-posted questions, comments, replies, try the search box just below, or if you prefer, post a question or comment in the Comments box below and we will respond promptly.

Search the InspectApedia website

Comment Box is loading comments...

Technical Reviewers & References

Click to Show or Hide Citations & References

Publisher's Google+ Page by Daniel Friedman