Deterioration of Owl-Flex™ brand Flex Duct in Air Conditioning or Heating Systems
Role of UV light exposure & heat in gray flex duct deterioration in buildings
Defective duct products and materials
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This chapter of "How to Inspect the Central Air Conditioning or Cooling System" describes the
Owl brand gray flex duct disintegration as an example of
defective heating or cooling ductwork materials such as Owl flexduct and also Goodman gray flex-duct, and some (not all) Owens Corning Flex-duct products.
Photo of deteriorated Owl brand gray flex duct and the suggestion of possible UV degradation of flex duct (in addition to heat) are courtesy of Eric Van De Ven.
This chapter discusses Owl Flex Duct failures with references to product failures by three manufacturers of flexible duct work,
Owl™, Owens Corning™ and Goodman™. Neither of these products is currently sold (2006) but both may be found in older homes. Not all
Owens Corning ducts share this defect and disintegration problem.
Air conditioning duct system defects include a remarkably wide range of errors, from failure to supply cool air or failure to even circulate air
in the building, to health hazards such as use of asbestos material in or on duct work, to very dangerous conditions such as drawing heating
equipment combustion gases into the building cooling (or heating) air.
This photo of Owl-flex™ gray plastic-covered, fiberglass insulated duct material shows damaged gray plastic covered flexible ductwork near a fluorescent light bulb.
Or page top photo, also taken in the same building by Eric Van De Ven shows the brand name on ductwork installed in the building.
Owl-flex flexible ductwork has been the subject of litigation, as shown in this flex duct lawsuit document filed in 2009.
As with the Goodman flex-duct problem described at GOODMAN GRAY FLEXDUCT, and also at in hot attic spaces or where exposed to UV light, the Owl-Flex flexible air conditioning
duct material disintegrates leaving its fiberglass insulation exposed to also disintegrate, leak, or possibly blow into
the building living space.
Does Exposure to a Nearby UV Light Also Cause Gray Flex Duct Damage?
Two common sources of deterioration in plastics are heat and UV light.
UV Light as a Source of Gray Flex Duct Deterioration
A fluorescent bulb contains low pressure mercury vapor, a gas that produces invisible ultraviolet light (UV radiation) when the gas is excited by electricity. Phosphorescent coating on the inside of the fluorescent light tube absorbs the UV radiation and converts it to visible light.
According to General Electric, a manufacturer of fluorescent light bulbs,
Regular fluorescent light bulbs used in your home and office do not produce a hazardous amount of ultraviolet light (UV). Most light sources, including fluorescent bulbs, emit a small amount of UV, but the UV produced by fluorescent light bulbs is far less than the amount produced by natural daylight. (Ultraviolet light rays are the light wavelengths that can cause sunburn and skin damage.)
But bringing up the sun does not address the impact of UV on thin plastic covering flexible ductwork.
UV absorption and polymer degradation occurs when polymers such as polypropylene and polyethylene absorb UV light causing weakening of molecular bonds at weak points in the polymer chain. So since many polymers are degraded by exposure to UV light, and therefore many plastics are damaged and made brittle by UV light, the close proximity to the bulb is a very strong suggestion.
Heat as a Source of Deterioration of Gray Plastic Covered Flex Ductwork
Heat is also a factor in plastic degradation, which may explain why more of the Goodman, Owens Corning, Or Owl type gray flex duct deterioration was in (hot) attics. Wikipedia: "Polymers are susceptible to attack by atmospheric oxygen, especially at elevated temperatures encountered during processing to shape." Presumably also in a hot attic heat is a well understood factor in plastic deterioration such as plastic covering flexduct.
A UV light also gives off some heat, though usually less than a typical incandescent bulb. So heat from a UV light very close to the plastic duct cover may also be a factor in deterioration.
The hypothesis that gray flex duct deterioration close to a fluorescent bulb is strengthened if the damage was less or absent on the same material where it was more distant from or not exposed at all to the UV light from the bulb, but where otherwise it was of the same age in the same general building conditions (such as exposure to temperatures).
When a flex-duct product has lost its exterior plastic covering the effects are these:
The cost of heating or cooling the building is increased due to lost insulation: because the ducts are no longer insulated from the ambient temperature in the attic or crawl space where they are located. For example, an air conditioning duct passing through a hot attic and missing its insulation will be heated by the ambient attic air, delivering warmer air to the living space than is desired.
The cost of heating or cooling the building is increased due to leaks: because damaged ducts are more likely to leak, cooled or warmed air intended for the occupied space may be lost in the attic or crawl space where the damaged HVAC ducts are located.
In addition we might see these two indirect problems developing:
Increased circulation of fiberglass particles from the duct insulation or from building insulation which may be picked up and blown into the building air supply
Mold growth in the HVAC ducts due to loss of insulation and increased in-duct condensation in some circumstances.
Replacement of the heating or air conditioning flexible sections of duct work is required - a significant expense which will be greater if flex-duct needs to be replaced where it passes through inaccessible areas such as finished walls or ceilings.
Notice that not all flex-duct products will fail in this manner
and unless you specifically find evidence of this deterioration, replacement of the flex-duct in a building may not be warranted. Where this duct is found in a building it should be replaced.
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Thanks to Eric Van De Ven,
Owner/Inspector, Magnum Inspections Inc., 954-340-6615 ev@magnuminspections.com for photographs of deteriorated Owl™ brand gray flex duct near a fluorescent light fixture and for technical discussion of this topic.
Flexduct lawsuit, Richard T.D. Bethea et als, v. Song Hee Hong, et al, filed may 29, 2009, Jackson Tennessee Court of Appeals, dispute involving the contract for sale of a house. A musty odor was associated with mold contaminated flex duct in the building. The ductwork could not be cleaned because of its fragility - an Owl-flex duct product. Sellers (correctly) asserted that the ductwork could not be cleaned. The court finding includes the statement that "OWL FLEX ductwork was uncleanable". The buyers ability to terminate the sales contract was upheld.
Thanks to Mark Cramer, Tampa Florida, for assistance in technical review of the "Critical Defects"
section and for the photograph of the deteriorating gray Owens Corning flex duct in a hot attic. Mr. Cramer is a Florida home inspector and
home inspection educator.
Thanks to Jon Bolton, an ASHI, FABI, and otherwise certified Florida home inspector who provided photos of failing Goodman gray flex duct in a hot attic.
Mold in the air handler or duct work is discussed at AIR HANDLER UNITS chapter HOW TO PREVENT MOLD: Correct the Causes of Mold and Prevent Indoor Mold or other indoor environment problems.
The Wiki article on UV degradation is at http://en.wikipedia.org/wiki/UV_degradation
Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair
Our recommended books about building design, inspection, and repair, and about indoor environment testing, diagnosis, and cleanup are at the InspectAPedia Bookstore.
"Air Conditioning & Refrigeration I & II", BOCES Education, Warren Hilliard (instructor), Poughkeepsie, New York, May - July 1982, [classroom notes from air conditioning and refrigeration maintenance and repair course attended by the website author]
Carson Dunlop, Associates, Toronto, have provided us with (and we recommend)
Carson Dunlop Weldon & Associates' Technical Reference Guide to manufacturer's model and serial number information for heating and cooling equipment ($69.00 U.S.).
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The Mold Information Center: What to Do About Mold in Buildings, When and How to Inspect for Mold, Clean Up Mold, or Avoid Mold Problems
Environmental Inspection, Testing, & Diagnosis On-Site IAQ, Gas, Air Testing, Mold Investigation, Sick Building Diagnosis, Lab Services, & Remediation Plan Preparation - indoor air quality testing, problem source determination, supporting lab work, written remediation plan addressing removal of environmental and other hazards and prevention of their recurrence.
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