Probable mold in ductwork

[jimcmd]

Opinions requested on presence of mold inside trunklines. Have 2 main trunks which are sheet metal with fiberglass insulation inside. I "scoped" both trunks yesterday and found one to be completely infested with what appears to be mold (tests pending) and the other to be about 1/2 way infested. Likely we will replace the ductwork, but I just want to make sure that there are no other options which are equivalent (cleaning with fungicide, etc.). The moisture source apparently came from the unit once having had a humidifier, but apparently removed before I bought house. Also, is there any better material than sheet metal/insulation which could be used to construct the ducts? thanks.

[Thebil Illpay]

Opinions requested on presence of mold inside trunklines. Have 2 main trunks which are sheet metal with fiberglass insulation inside. I "scoped" both trunks yesterday and found one to be completely infested with what appears to be mold (tests pending) and the other to be about 1/2 way infested. Likely we will replace the ductwork, but I just want to make sure that there are no other options which are equivalent (cleaning with fungicide, etc.). The moisture source apparently came from the unit once having had a humidifier, but apparently removed before I bought house. Also, is there any better material than sheet metal/insulation which could be used to construct the ducts? thanks.

http://www.epa.gov/iaq/schools/tfs/guideh.html

Read and digest this and you will come to the only possible conclusions: A) that if you indeed have mold growing in your ducts the humidity in the ducts is likely too high and the currently growing mold isn't a result of some humidifier removed in the past and, B) if there is mold growing it is growing on organic material that has accumulated on the fiberglas insultaion. {I'm not sure this is spelled out in the article: that mold needs organic material to feed on}

[drk]

You could have the duct cleaned and sprayed with BBJ. Then coat the liner with Foster 40-20 will be allot cheaper than replacing. If you replace just go with sheet metal wrapped on the out side.

[wahoo]

Couple of good earlier posts! If you decide to replace ductwork, and wrap the outside, be aware of possibility of increased "air noise" if you also have metal pipes to your outlets. Our experience has been that the removal of internal insulation on main ductwork with the use of metal pipes will increase noise levels. But the inside of the ductwork is easier to clean. The "black" specks you are seeing may be the flacking of the "mat" on the surface of the ductlining insulation, and actually not be mold at all (hopefully). You mentioned that you had sent it off for testing. Good move.

[jimcmd]

The "specks" are not black, but very numerous white circular growths which cover a large portion of the black insulation. What is the efficacy of duct cleaning/treatment if it indeed turns out to be mold. (insulation inside)

[Thebil Illpay]

The "specks" are not black, but very numerous white circular growths which cover a large portion of the black insulation. What is the efficacy of duct cleaning/treatment if it indeed turns out to be mold. (insulation inside)

As this isn't an HVAC question, I suppose I can try to answer it for you. It's basically kind of common sense. The efficacy at the time it is done is, for all practical purposes, 100%. The mold has been cleaned off, it's gone, period. If you don't control the humidity to a level below that at which the mold can grow, if there is organic material on which to grow, it grows back.

[bigtime]

Air leaving a cooling coil is has a relative humidity of close to 100%. How can you not have humid air in a air conditioned supply duct?

[drk]

Foster 40-20 will prevent future mold so it will not grow back on the coating.

[Thebil Illpay]

Air leaving a cooling coil is has a relative humidity of close to 100%. How can you not have humid air in a air conditioned supply duct?

Good question. The humid air leaving the coil shouldn't have the chance to condense on the insulation. [The mold won't grow unless the water condenses on or is absorbed by an organic material bearing material. This is an HVAC question. Read the same EPA publication I referenced and you'll come across references to moving air. Apply your knowledge. I'm not crossing that line.

I should have added earlier that you can eliminate the water OR the food source.

[jcarneal]

Ran into this exact problem once. Lab tests of swabs are pretty much useless except to tell you the kind of mold. If you're seeing growth, you can bet it's mold.

We ended up ripping out the ducts and putting in all new with insulation on the outside. This should eliminate organic material getting trapped in the ducts in the first place, eliminating or reducing the chances for further growth.

If you're going to attempt to clean it out (I wouldn't), I'd recommend an airborne mold test by a professional mold remediation service after you're finished to ensure that the mold has actually been removed. If you're still getting too high a ppm mold reading (don't remember the numbers myself) on that test, you'll have to go to more drastic measures.

Good luck.

[Thebil Illpay]

Ran into this exact problem once. Lab tests of swabs are pretty much useless except to tell you the kind of mold. If you're seeing growth, you can bet it's mold.

We ended up ripping out the ducts and putting in all new with insulation on the outside. This should eliminate organic material getting trapped in the ducts in the first place, eliminating or reducing the chances for further growth.

If you're going to attempt to clean it out (I wouldn't), I'd recommend an airborne mold test by a professional mold remediation service after you're finished to ensure that the mold has actually been removed. If you're still getting too high a ppm mold reading (don't remember the numbers myself) on that test, you'll have to go to more drastic measures.

Good luck.

Nothing that you have stated is bad advice. However, I'd clean it out and have the fiberglas coated for a few feet. The mold likely doesn't extend more than a few feet, if that even. The reason I'd do this is common sense combined with some intelligence. Mold spores are all around your home. They can not be eliminated -we're talking about a house here. You can change the duct but all it takes is for one of the installers to have some mayo on his fingers during the install and - poof- mold colony.

You've got to remember that all the mold hype started with one lawsuit about black 'toxic' mold.

And if I'm wrong about any of this, enlighten me.

[jcarneal]

Nothing that you have stated is bad advice. However, I'd clean it out and have the fiberglas coated for a few feet. The mold likely doesn't extend more than a few feet, if that even. The reason I'd do this is common sense combined with some intelligence. Mold spores are all around your home. They can not be eliminated -we're talking about a house here. You can change the duct but all it takes is for one of the installers to have some mayo on his fingers during the install and - poof- mold colony.

You've got to remember that all the mold hype started with one lawsuit about black 'toxic' mold.

And if I'm wrong about any of this, enlighten me.

I'm not qualified to enlighten anyone :)

You're right, mold spores are in the air inside and out all the time. The problem, as I understand it, is that once you have a concentrated source in something like a trunk line, you increase the ppm of mold spores to unacceptable levels vis a vis the baseline of outdoor air quality. And due to better and better insulation in todays homes, that newly "contaminated" air doesn't have an opportunity to cycle often enough to dilute the excess particles.

People who are sensitive to airborne allergens are therefore more likely to develop respiratory problems and other ad hoc illnesses even if the mold is of the most common, innocuous types (aspergillus or penicillium). If it's more toxic stachybotrys, it can lead to a host of unpleasant, and long-lasting problems.

As to it extending only a few feet, that's a good point and worth checking out. Problem we had is that it did pervade the entire trunk line. You can easily check this by randomly removing a branch line at different spots on the trunk and shine a light in. The growth is more than likely readily visible if it's there.

One last point to the OP, I'd definitely recommend you consider the liability ramifications of whatever fix you implement. If the mold comes back and someone gets sick later and you are deemed to have been responsible for an insufficient fix, a sympathetic jury is going to have a field day with you.

In fact, depending on your state, you may not be qualified to do anything at all. Some states now require licensed mold companies with complex encapsulation and osmosis/filtration techniques to be set up during the remediation process so as not to contaminate the rest of the home during removal.

I'm not saying I agree with all this mess, just pointing out that's the way it is. Personally I think the whole mold thing is way overblown (no pun intended), but that's another post :)

[drk]

As far as testing the mold it really doesn't matter what kind of mold it is. Money would be better spent in treating the mold. As far as the equipment goes any good duct cleaning company that uses negative air equipment (not rotobrush junk) will have the equipment to remove the mold. This is very common we do at least one job per week that has lots of mold in the HVAC system.

[francosair]

Talk to a good IAQ (indoor air quality) specialist on your area and also to your a/c contractor they will help you to aviod future health, and building prblems.

[jimcmd]

Cut holes in length of both trunk lines and both are completely infested. Looks like a freaking mushroom farm growing inside. Maybe I can harvest some truffles and pay for this system. In any event, ripping it all out, starting fresh. Going with a carrier 95 percent furnace and a 17 seer a/c.. adding the filter and the uv light. Got lots of quotes, and just like skinning a cat, got as many different opinions. Thanks for all who contributed to this thread. I certainly have learned more than I ever thought about HVAC... If there are any mushroom, mold, or truffles fans out there, please let me know and I will send you my old ductwork.

[HRPGuam]

Here is my problem:

First I am from Guam and we do not have heating here. Outside temperature is almost 89 degrees everyday and drops to about 80-85 degrees at night. I have a metal building with some interior batt insulation. Now I have a drop ceiling which separates the inside from the ceiling space. I have duct board duct work coming from a 5 ton unit mounted inside a closet. Return is not ducted.

My ceiling tiles have mold on them coming from the water that is condensing on the duct work and then dripping into the tiles. It is worst around the diffusers.

It seems like there is not enough air circulating inside that ceiling space even though there are a few holes on the existing ducts to get some air inside the ceiling space. I was thinking of replacing the unit with a 7 ton unit and get more air into the space.

Do you think this will solve my mold issues? Do I need to replace the ductwork?

Thanks,

[genduct]

As your second post stated, Mold needs organic material to grow (DIRT) so when dirt and liquid water (already pointed out that AC has almost 100% RH) then BUGS can grow.
The thermal bridge of connectors with sheet metal duct or ripped vapor barrier of wrap make keeping water (sweat) from getting inside sheet metal duct challenging.
IF you are really concerned I think you could demo and replace the infested trunk with fiberglass ductboard trunk for less than cleaning and treating the existing duct.
Ductboard by its design doesn't have the thermal bridge or vapor barrier problem.

You have to have insulation if you don't want the sweat/ extra liquid water.
Good luck

[teddy bear]

Here is my problem:

First I am from Guam and we do not have heating here. Outside temperature is almost 89 degrees everyday and drops to about 80-85 degrees at night. I have a metal building with some interior batt insulation. Now I have a drop ceiling which separates the inside from the ceiling space. I have duct board duct work coming from a 5 ton unit mounted inside a closet. Return is not ducted.

My ceiling tiles have mold on them coming from the water that is condensing on the duct work and then dripping into the tiles. It is worst around the diffusers.

It seems like there is not enough air circulating inside that ceiling space even though there are a few holes on the existing ducts to get some air inside the ceiling space. I was thinking of replacing the unit with a 7 ton unit and get more air into the space.

Do you think this will solve my mold issues? Do I need to replace the ductwork?

Thanks,

You need several hours of <50%RH everyday to be assured of no mold growth in damp places. This includes some dry time for the inside of your a/c ducts. Attic spaces can not have extended hours of sweating ducts. You must have adequate insulation to avoid near condensation in the non-conditioned space or seal the non-conditioned space and dehumidify the space to <50%RH during the cool hours of the day.
You are going to need some supplemental dehumidification when the cooling load is not high enough keep the space dry with a/c only.

We recently bid a armed services barricks project that was designed with supplemental dehumidification to maintain <50%RH all the time. This included daily drying out of the a/c ducts for several hours eveyday. Check the Ultra-Aire install manuals for suggestions.

A local engineer designed the systems.
A larger a/c may not help unless you are unable to maintain the desire temperatures during the hottest weather.
Regards TB

[Jack2007]

Here is my problem:

First I am from Guam and we do not have heating here. Outside temperature is almost 89 degrees everyday and drops to about 80-85 degrees at night. I have a metal building with some interior batt insulation. Now I have a drop ceiling which separates the inside from the ceiling space. I have duct board duct work coming from a 5 ton unit mounted inside a closet. Return is not ducted.

My ceiling tiles have mold on them coming from the water that is condensing on the duct work and then dripping into the tiles. It is worst around the diffusers.

It seems like there is not enough air circulating inside that ceiling space even though there are a few holes on the existing ducts to get some air inside the ceiling space. I was thinking of replacing the unit with a 7 ton unit and get more air into the space.

Do you think this will solve my mold issues? Do I need to replace the ductwork?

Thanks,
I'll just tell you about my past system. I HAD a 5 ton AC with duct board ducts. The inside of the duct board was filled with mold because (according to the contractor) my system was so over sized that it was NOT getting rid of the excess moisture.

The humidity in my home was always >65% in the summer.

Since I went to a smaller two staged system, my humidity is always <50%, usually in the mid 40% range in the summer.

.

[genduct]

JACK, it's nice to hear that a 2 stage system, no doubt running longer at the lower capacity solved your RH problem. This seems to be the root of 30% of the posts on this site.
That being said, the mold on the inside of your duct was because the filters must not have been changed routinely and dirt was present with LIQUID WATER so you then grew BUGS. All duct sees almost 100% RH supply air during the cooling season so high Rh IN the duct is not the problem only when the condensation is allowed to enter the duct.
Too bad you contractor didn't know that or you may have misunderstood his remarks.

[HRPGuam]

Thanks for the information guys. One contractor suggested I install an exhaust for the attic space? Any thoughts on this?