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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. Readers should see HEAT LOSS in BUILDINGS. Also see AIR SEALING STRATEGIES and AIR LEAK DETECTION TOOLS as well as AIR LEAK MINIMIZATION. For photos of snow melt on rooftops that also show points of building heat transfer and loss, see STAIN DIAGNOSIS on Building Exteriors. Thermal tracking 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. Thermal tracking, sooting, bridging, and ghosting are synonyms for the same effect, one which often is exacerbated by defects in the building insulation and ventilation system. 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 EXPERT, WHEN TO 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. © Copyright 2010 Daniel Friedman, All Rights Reserved. Information Accuracy & Bias Pledge is at below-left. Use links at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website. A Photo-Illustrated Diagnostic Guide to Thermal Tracking & Other Wall or Ceiling Stains: Moisture & Air Movement in BuildingsWhat is Thermal Tracking & Why does Thermal Tracking or Thermal Staining Occur Indoors?
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. 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. This interior black wall stain pattern is particularly easy to identify on walls - see Wall Thermal Tracking Stains. 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. So 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.
SAFETY WARNING about Thermal Tracking or Ghosting Black Stains Indoors
Air Leaks or Insulation as Causes of Thermal Tracking or Indoor Ghosting MarksInsulation 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 & VENTILATION 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. Humidity as a Factor in the Development of Indoor Stains on Building SurfacesHigh indoor humidity: 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. Thermophoresis as a Factor in the Development of Indoor Stains on Building SurfacesWhen condensation occurs on a building surface at any level that makes that area more damp (and thus sticker) than its neighbors, the temperature and humidity-related particle deposition described above is almost certainly occurring in any building, and will be more noticeable in a building with high levels of airborne particulates and dust. But as IAQ consultant Steven Temes, an industrial hygienist and microbial consultant points out, ultrafine carbonaceous particles (such as candle soot) also accumulate on the colder surfaces due to a little known physical phenomenon called thermophoresis. This has to do with the driving force of the particle motion being its kinetic energy (when not overwhelmed by air currents) and the movement of the particle toward the cold surface, where it "plates out", adhering to the surface. If the particle has an electrical charge (such as in a home where ozone generators or negative ion generators are in use) this plating-out process will be significantly increased. If you are using an ozone generator as an "air purifier" indoors, be sure to review OZONE AIR PURIFIER WARNINGS and also OZONE HAZARDS. Indoor Air Particle Level as a Factor in the Development of Indoor Stains on Building SurfacesEven if the building humidity levels are low, high levels of indoor dust and debris can still lead to indoor stains and thermal tracking marks. Significant sources of soot, such as improperly operating heating equipment, use of candles, fireplaces, woodstoves (if they release smoke into the building interior), some pets such as large dogs, or simply generally poor housekeeping can all increase the indoor air particle level and lead to soot and stain marks. Usually soot marks, thermal bridging, or thermal tracking stains appear, if at all, in the building interior locations discussed in the remaining sections of this article. Air Movement Patterns as Factors in the Development of Indoor Stains on Building SurfacesSpecific 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. Multiple Complex Factors Determine Where Stains Appear in BuildingsConflicting variables are at work in the deposition of soot and debris on building surfaces. Here are some examples:
Visual Inspection by an Expert can Usually Sort Out the Causes of Building StainsConceptually, 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. In the following sections of this article we describe the ways that stains appear in buildings, what causes these stains, what they mean for building condition and safety, and how they can be cleaned, remedied, and prevented in the future. ... Technical Reviewers & References
Use links just below or at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website. THERMAL TRACKING & THERMAL BRIDGINGWhat is Thermal Tracking Ceiling Thermal Tracking Marks Wall Thermal Tracking Stains Floor Carpet Thermal Tracking Stains Air Bypass Leaks Marks on Insulation Thermal Tracking to Diagnose IAQ Stains HVAC Supply Registers Pet Stains on Floors Pet Stains on Walls Human Occupant Stains on Walls Stains from Candles, Woodstoves, Fireplaces Other Stains on Indoor Walls & Ceilings What to Do About Thermal Tracking SIDING WOOD STAIN DIAGNOSIS on Building Exteriors STAIN DIAGNOSIS on Indoor Surfaces STAINS on Indoor Surfaces: PHOTO GUIDE CARPET TEST GUIDE also see Investigation of Indoor House Dust Debris
Building Air Leaks & Thermal Tracking Marks at Interior Ceilings
Air Leaks Causing Thermal Tracking Stains on Building Walls
Heaters can cause other dirt or soot stains on walls: But beware, a baseboard heater itself causes an air convection current up through the heating baseboards and in a dirty home or in a home occupied by pets or smokers similar stains may appear on other building interior walls (such as in this photograph) even if the wall is well insulated. If staining appears vertical and at intervals thermal tracking is probably occurring. How to Recognize Air Bypass Leaks and Thermal Bridging Marks on Fiberglass Insulation
How to Use Indoor Stains Like Thermal Tracking to Diagnose Building Air Leaks, Insulation Defects, and Indoor Air Quality ProblemsSignificance of Other Indoor Stains and Marks for Building Framing Location or Defects in Heating & Cooling System OperationSince thermal tracking, or soot marking, or "thermal bridging" always tell us about missing or openings in building insulation or about air leaks, we can learn other facts about a building such as those listed here:
How "Read" Indoor Stains to Identify Indoor Air Quality ConcernsA 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. How to Diagnose Stains and Debris at Ceiling and Wall Heating or Cooling Air Supply Registers
How to Recognize Pet Stains on Building Walls
How to Recognize Wall Stains from Human Occupants
How to Recognize Wall or Ceiling Stains due to use of Candles, Woodstoves, or Fireplaces
Thermal tracking on buildings combined with this evidence can also be a clue useful in diagnosing indoor air quality complaints. In these photographs, all of the stains visible appear due to use of candles. Note the absence of framing-interval staining (16" or 24" on center) which would have been characteristic of thermal tracking, even of the candle soot, had the building surfaces been cool due to poor insulation. Excessive indoor humidity: If indoor humidity is too high we may be encouraging mold growth in a building or we may be inviting excessive levels of dust mite activity which in turn increases the level of allergens in the building. Other Sources of Dark Stains on Indoor Walls & CeilingsIf you have frequent fireplace fires, cooking, or if you burn scented candles, if people smoke in your home, or if your oil-fired or gas-fired heating system is not working properly, the added soot particle load in the building air is not only a health concern (soot and potentially lead), it also will mark the building surfaces in this characteristic pattern. We welcome more thermal tracking, soot tracking, air bypass leaks, and similar photos of indoor stains as well as text suggestions to expand this detail and would be glad to credit contributors. |
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06/19/2009 - 10/22/2007 - InspectAPedia.com/interiors/ThermalTracking.htm - © 2010 - 1988 Copyright Daniel Friedman All Rights Reserved - InspectAPedia® is a Registered U.S. Trademark