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AIR CONDITIONING & HEAT PUMP SYSTEMS
A/C - HEAT PUMP CONTROLS & SWITCHES
AIR CONDITIONER COMPONENT PARTS
AIR CONDITIONER TYPES, ENERGY SOURCES
AIR FILTER EFFICIENCY
AIR FILTERS, FIBERGLASS PARTICLES
AIR FLOW MEASUREMENT CFM
APPLIANCE DIAGNOSIS & REPAIR
APPLIANCE EFFICIENCY RATINGS
BLOWER DOORS & AIR INFILTRATION
BLOWER FAN CONTINUOUS OPERATION
BLOWER FAN OPERATION & TESTING
BOOKSTORE - Air Conditioning "How To" Books
CAPACITORS for HARD STARTING MOTORS
CLEANING & Legionella BACTERIA
CHINESE DRYWALL HAZARDS
CONDENSATION or SWEATING PIPES, TANKS
DEFINITION of HEATING & COOLING TERMS
DEW POINT CALCULATION for WALLS
DEW POINT TABLE - CONDENSATION POINT GUIDE
DIAGNOSTIC GUIDES A/C / HEAT PUMP
DIAGNOSE & FIX HEATING PROBLEMS-BOILER
DIAGNOSE & FIX HEATING PROBLEMS-FURNACE
DUCTS - Asbestos
DUCT INSULATION, Asbestos Paper
DUCT INSULATION for SOUNDPROOFING
DUCT SYSTEM & DUCT DEFECTS
DUCT SYSTEM NOISES
DUCTS, Asbestos Transite Pipe
DUST, HVAC CONTAMINATION STUDY
ELECTRIC MOTOR OVERLOAD RESET SWITCH
EVAPORATIVE COOLING SYSTEMS
FAN LIMIT SWITCH
GAS EXPOSURE EFFECTS, TOXIC
GAS DETECTION INSTRUMENTS
HEAT LOSS (or GAIN) in buildings
HEAT LOSS (or GAIN) INDICATORS
HEAT LOSS R U & K VALUE CALCULATION
HEATING SMALL LOADS
INSPECTION CHECKLIST - OUTDOOR UNIT
INSPECTION LIMITATIONS, A/C SYSTEMS
LEED GREEN BUILDING CERTIFICATION
LOST COOLING CAPACITY
LOW VOLTAGE TRANSFORMER TEST
MOTOR OVERLOAD RESET SWITCH
MOLD in AIR HANDLERS & DUCT WORK
OPERATING COST, AIR CONDITIONER
OPERATING DEFECTS, AIR CONDITIONING
REPAIR GUIDES A/C / HEAT PUMP
REPAIR & DIAGNOSTIC FAQs for A/C
THERMOSTATS, HEATING / COOLING
THERMOSTATIC EXPANSION VALVES
WATER COOLED AIR CONDITIONERS
WINDOW / WALL AIR CONDITIONERS
WINDOW / WALL A/C SUPPORTS
Mechanically-damaged HVAC ducts: this article describes damaged HVAC ducts due to some mechanical activity such as stepping on a duct and crushing it, or improper and too-aggressive duct cleaning methods that damage duct interior surfaces, liners, or binding resins.
This article series discusses duct system defects such as missing air conditioning cool air supply or return air registers, undersized air conditioning duct openings, improper cooling duct routing, cooling (or heating) air duct corrosion, leaky air duct connections, defective heating or cooling ductwork materials such as Goodman gray flex-duct, some Owens Corning Flex-duct, and asbestos-containing air conditioning or heating duct work.
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At left our photo, provided by reader Steven King, shows the interior of fiberglass-lined flexduct that has been crushed, perhaps by having been stepped-on?
The result is reduced heating or cooling air flow, reduced building occupant comfort, and higher heating or cooling system operation cost.
We were also concerned that the exposed fiberglass in the duct appears to have been mechanically damaged, perhaps by a too-aggressive attempt at duct cleaning that may result in higher levels of airborne fiberglass duct insulation fragments in the building.
Other crimping and blockage or support problems found in flexduct installations are discussed at DUCT ROUTING & SUPPORT.
This photo shows the connection of fiberglass flex duct to a metal HVAC duct component. The fiberglass flex duct has been badly damaged.
As this photograph of duct damage was taken at the same installation as the example above, we suspect that an inexperienced duct cleaner has been at work here.
Water flooding in ductwork also ruins it and is discussed at WATER & ICE IN DUCT WORK
But when the metal sheeting nailed across the floor joist bottoms has rusted out, severe air leaks occur.
In a supply duct the result is higher heating or cooling costs. In a return air duct a hole such as the one shown in our photo can cause unhealthy or unsafe conditions by drawing other unanticipated air into the duct system (in this case next to a crawl space vent we are basically heating outdoor air and blowing it into the living area).
At below right we illustrate the rust (and rodent infestation) found in an in-slab metal spiral air duct. SLAB DUCTWORK - catalogs the functional and environmental problems found when HVAC air ducts are routed in or below floor slabs
Watch out: large improper openings in return ductwork, whether from rust or any other causes, can cause building backdrafting and dangerous carbon monoxide hazards. See UNSAFE DUCT OPENINGS and see BACKDRAFTING HEATING EQUIPMENT.
Illustrations of a leaky cast iron sewer line that sent sewer gases into the building's transite (asbestos cement) heating duct system can be seen at TRANSITE PIPE AIR DUCTS and at CAST IRON DRAIN PIPING.
Damaged or Lost HVAC Duct Insulation
Reader Question: is thi normal wear on the insulation on my duct work? Should I be worried about mold contamination?
Had an insulation question. Hopefully you are able to view the attached pictures. Do you think this is normal wear to the insulation around the Duct work or should I be concerned about the possibility of mold contamination? - J. 3/31/2014
I'm not sure what I'm looking at in your photos but it looks as if fiberglass insulation has been lost around the outside of galvanized metal HVAC ductwork.
If that's so the results are increased operating costs & risk of in-duct condensation and moisture-related problems (mold for example).
For a discussion about whether or not you can find mold in fiberglass - yes - see FIBERGLASS INSULATION MOLD
Causes of mold growth in HVAC ductwork - mold in air ducts at WHY DOES MOLD GROW in INSULATION? for a discussion of possible mold growth in fiberglass insulation in general.
Generally if I see ducts like this I expect that all of the original installation was on the duct exterior - where it doesn't produce much of a particle hazard to air flowing inside the ducts except in the event of duct leaks in the return air system. (See AIR LEAKS in RETURN DUCTS).
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Frequently Asked Questions (FAQs)
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Question: Un-lined Flex Ducts Exposes Fiberglass in My Home - is this OK?
I have attached my photos. You are welcome to use them on your website if it can help someone. Perhaps, it could help someone properly come to a conclusion and solution. Your assistance and help would be greatly appreciated. Sincerely, - A.G. 10/11/2012
Reply: Cleaning, Maintenance, Repair/Replace or Re-Line Suggestions for Un-Lined or Incompletely-lined Flex-Duct
A competent onsite inspection by an expert usually finds additional clues that help accurately diagnose a problem with an HVAC system, duct work, or often other more urgent building concerns that an owner or occupant may not have noticed. That said, I have taken a look at your photos and from what I can see:
Yes, normally flex-duct used in HVAC systems includes a plastic or vinyl interior liner and an external cover as well, leaving the fiberglass duct insulation sandwiched between the two. In my OPINION and based on your pictures
My recommendations for un-lined HVAC flex duct:
Question: six feet of damaged ductwork - health concerns?
I live in CA and had a new AC System installed about 7 years ago. I had it serviced by the company that installed it the first 5 years or so and they sold out to another company. Since then I have used that company until the last service. The company that came out told me the first 5 or 6 six feet of my duct was the old original Fiberglass duct.
I didn't think much about it at the time, but I recently had my ducts cleaned. This company told me the same thing and advised me to contact the installing company. They are now in AZ , and the company that took their clients won't respond to me. I have been told this could be dangerous. Can you tell me what government agency I would contact to see if there is anything I can do about it? My wife and I and our two dogs all have bad allergies and it could be related. Thank You for your response. - R.B. 3/24/2013
I'm not sure what government agency is going to get involved in the case you described, though you might obtain some advice from your local health department. For some help in deciding if it is appropriate to hire an environmental expert to examine your home for allergens, mold, or other health risks that could contribute to the allergy complaints you cite, please take a look at MOLD EXPERT, WHEN TO HIRE.
Just from your description we can have no idea if the ducts are hazardous, or if so, in what form. Indeed if the ductwork was fiberglass lined and was mechanically damaged by improper cleaning it might make sense to replace it.
Questions & answers or comments about the types of damage found in HVAC air ducts.
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