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Photograph of  thermal tracking or soot tracking - cool surface, moisture condenses, soot is deposited - Daniel Friedman 02-12-16 How to Recognize & Diagnose Stains on Building Walls - Causes of High Heating Costs
InspectAPedia®  -    

  • How to Recognize & Diagnose Thermal Tracking, Soot Stains on Building Walls - Diagnosing Causes of High Heating Costs
  • 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
Our site offers impartial, unbiased advice without conflicts of interest. We will block advertisements which we discover or readers inform us are associated with bad business practices, false-advertising, or junk science. Our contact info is at InspectAPedia.com/appointment.htm.

This article describes How to Recognize & Diagnose Thermal Tracking, Soot Stains on Building Walls - Diagnosing Causes of High Heating Costs and discusses other various interior wall and ceiling stains and explains how to recognize thermal tracking, thermal bridging stains, building air leaks, and building insulation defects. Often these stains are mistaken for toxic indoor 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.

These are substances that cause black sooty marks on building interior ceilings or walls and sometimes also on carpets are from sources and causes that you can easily learn to recognize in buildings. Save your mold test money, and increase the accuracy of your mold contamination inspection or test for toxic or allergenic mold in buildings: review these items to learn recognize non-fungal materials or even possibly harmless cosmetic "black mold" often mistaken for "toxic fungal growth."

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.

© 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.

Air Leaks Causing Thermal Tracking Stains on Building Walls

Thermal bridging or thermal tracking soot stains on interior walls (C) Daniel Friedman



Thermal tracking stains may appear on the building walls themselves, in a pattern of vertical "stripes" which may be roughly 16" or 24" on center, marking the (cooler) location of wall studs or ceiling joists.

In this case the exterior wall surface (see that window at right in the photo) are cooler where the wall studs are located and warmer between the wall studs. Probably the wall cavity is insulated, and the insulated areas have a higher "R" value than the solid wood studs themselves.

So the wall is cooler where the studs are located, increasing condensation on those surface areas, and picking up a greater share of house dust in air moving across those surfaces.

Thermal tracking stains may appear as dark black/brown wall stains appearing close to floor level, above heating baseboards mounted on exterior walls are probably due to thermal tracking.

Wall Stains over Heat Sources such as Hot Water Baseboards

Photograph of thermal tracking on an indoor wall
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.

The stain and soot deposition pattern over heaters is complicated by variations in the heat and air movement coming out of the heat source, and may not always accurately map wall stud or insulation locations.

More wall stains from heat sources such as over an air supply register in a floor are described at Other Stains on Indoor Walls & Ceilings and ceiling stains from heating or air conditioning registers are described at Stains HVAC Supply Registers.

Why Black Stains May Appear on Building Interior Walls as Well as on Building Exterior Walls

Our photo at below left shows wide black rectangular stains on a wall where insulation was omitted. The photo at below right shows long narrow black stains on a wall where thermal tracking marked the location of wall studs, but where insulation was present. Why did both of these patterns appear in the same building?

High interior moisture (air handlers in wet crawl spaces, a wet basement) was most likely the determining factor in the extent of staining that occurred in this home. Moisture condensed (and caused adhesion of house dust particles) on cooler surfaces. In some areas the un-insulated wall was coolest and got stained (below left) while in other areas the wall studs were cooler than the insulated wall cavity, so the stud-areas got stained (below right).

Thermal tracking on a wall missing insulation (C) Daniel Friedman Thermal tracking at wall studs (C) Daniel Friedman

Black, roughly rectangular stains on building interior or exterior walls: may be present wherever insulation has been omitted. While usually these stains are going to appear on the building exterior walls (which get colder) they may appear on interior walls as well. These stains on interior walls, which may be completely un insulated, may appear with greater severity where other construction details increase the flow of air and/or moisture in certain sections of wall cavity.

An example of the cause of this stain pattern is air movement up through the wall cavity from a cool, damp basement or crawl space. The heated building living space warms the open interior wall cavity, causing air in that cavity to rise by natural convection towards the building attic or roof cavity.

Air movement upwards in the wall cavity draws cooler air from the basement or crawl space. Where some wall sections have more air movement, less insulation, or greater moisture exposure, they may become more darkly stained than their neighbors or more darkly stained than other walls in the building interior.

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.

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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
  What is Thermal Tracking
  Ceiling Thermal Tracking Marks
  Wall Thermal Tracking Stains
  Floor Carpet Thermal Tracking Stains
  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
STAINS on Indoor Surfaces: PHOTO GUIDE
CARPET TEST GUIDE
also see Investigation of Indoor House Dust Debris
  • Thanks to Alan Carson, Carson Dunlop, Associates, Toronto, for technical critique and content suggestions regarding thermal tracking.
  • 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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ENVIRONMENTAL HAZARDS - INSPECT, TEST, REMEDY
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DIAGNOSE OTHER DARK STAINS on Indoor Surfaces
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