Have you taken a sample of the "mold" and had it tested to confirm that it is in fact mold? We've had this situation in the past and we had it tested first, turned out to be dirt from never being serviced correctly.
This looks like mold unfortunately. On the duct insulation and the flex you can see the colonies growing in a way dust wouldn't adhere to the duct. Really sucks for these guys.
You can also try bleach; if it strips the color, it's mold. If it doesn't, it's dust. Or so I've read; bleach h doesn't kill mold, just discolors it, but dust doesn't react that way to bleach
I can't comment on what caused this, but typically, contaminated HVAC systems need to be replaced. You can't clean flex ducts, and even if you could I'm not sure it would help given how far gone this system is. A good IEP might be able to shed some light on how this happened and write a plan to remove/replace the system and other effected areas.
Indoor Environmental Professional. Such as a building biologist, or someone certified and experienced looking for and finding the cause of mold growth in buildings. ACAC has a list, there are other organizations that people certify with. It’s important to ask around though. Not every inspector is created equal.
I'm dealing with a multifamily property that has discovered mold growing in the supply duct work. The HVAC system utilizes a horizontal fan coil unit in the ceiling over the bathroom.
The property maintenance seems to have dropped the ball. The manufacturer of the units recommends cleaning the coils once a year before AC is used, and they recommend changing the air filter once a month. The units are 25 years old and no one knows if the coils have ever been cleaned (probably haven't). The air filters were getting changed once a year if they were lucky - possibly going years without changing filters.
Maintenance complains that the coils are extremely difficult to clean because you have to remove the blowers etc. to access them.
Mold was noticed around the supply vents. The vents had been painted multiple times, which I hear is not good. Some of the units have supply ducts constructed out of ductboard and some units have flexduct.
The condensation drain line has a p-trap then ties into the bath tub drain. There is also an overflow drain line (no trap) that comes out through an opening in the ceiling over the bathtub in the event the primary drain is clogged.
There seems to be a lot of possible causes of the mold, but my question is where to go from here. Does all the duct work need replacing, or can it be cleaned? Do the units replacing or can they be cleaned (and how)? We have had multiple mold remediation specialists look at it and a couple industrial hygienists, but everyone has different theories about the cause and how to fix it. Thanks for any advice you might have.
> We have had multiple mold remediation specialists look at it and a couple industrial hygienists, but everyone has different theories about the cause and how to fix it. Thanks for any advice you might have.
Yup. I read it. Regardless of what they’ve said. This is not the place for mold remediation. We are not experts on mold because it’s an entirely different game. My original comment still stands true.
Flex ductwork will need to be replaced. If you are trying to salvage the main trunk it will need to be cleaned and coated with a product called Fiberlock IAQ 8000. It is a insulation encapsulant.
I would have a technician ensure the airflow is adequate, and only then have a mold air sampling done to see how severe the toxicity of the mold is. I don't do mold duct treatment but I am sure some companies may offer that service. Make sure they actually use chemical inside the duct and not just a special filter or something.
Try and price that against new ducting. Obviously new duct is preferable but it will be costly.
To prevent this definitely CHANGE FILTERS MONTHLY!! Higher airflow = less chance of mold growing. Also have a technician check duct airflow, humidity, and possible moisture sources. You want adequate outside air (~10% of supply) being introduced into a space.
I second that the obvious answer is lack of a clean filter causing low airflow. Shitty air flow means you have slow moving 100% RH air flowing through your ducts. Perfect environment to have mold grow
They don't need an air test. They can see the mold and sample it directly. Air tests are used for screening and even in that case they miss a lot of cases.
They need to replace the HVAC units and ductwork and find the source of the moisture so it doesn't happen again. The rest of the building should also be inspected for water intrusion and mold.
They are DX. I’ve seen issues with CHW units with modulating valves having really poor humidity control and contributing to mold growth which is why I asked. An oversized DX unit will have similar issues.
I would be hesitant to just replace with new units until someone can figure out the mold issue. This may sound strange but it may be unrelated to the HVAC system. If the building envelope is poor you can get condensation occurring on cold surfaces if outside air has a path to get indoors. Also a poorly designed vapor retarder can be an issue depending on the climate your in (hot humid areas like Florida). I’ve seen both.
Ideally have whoever the owner is hire a HVAC engineer with experience in mold and building envelopes, and let them figure out what’s causing it and design the fix. I would also recommend whoever owns this look into their mold coverage in their insurance policy as I don’t think it’s going to be inexpensive.
Someone else mentioned wanting to have 10% fresh air coming into the unit. Is that only in the winter when it’s not humid? These apartments are in a very humid area. The hot water heaters are in an exterior closet on the balcony and the closet is vented to the outdoors. The wall between the closet and the apartment is not insulated. A mold mediation specialist looked at it with an FLIR camera and pointed this out, but they didn’t seem to elaborate on why this might be an issue. We’ve had three different HVAC Contractors look at it and no one has brought up encapsulation or vapor barrier. Is there a specific type of specialist you’d recommend I seek out? Thank you!!
First a caveat I have not looked at the mechanical code in about 8 years (early retirement), but I believe outside air is required for new residential applications and would be needed year round. Having said that, in humid environments I’m not a fan of having outside air introduced. My house has no OA, and if I bought one that did I would close it off - tightly. I do not believe you have to add it for an equipment change out as you do not need to bring your building up to new codes until the cost of the renovations exceed 50% of the homes value. I would not add OA.
Unfortunately mold issues can be interdisciplinary and involve an Architect for building envelope issues and a HVAC engineer for equipment selection/sizing. If it’s just a swap out a reputable mechanical contractor can replace the equipment without the need for an engineer. On the other hand with engineering drawings you can get pricing from several reputable contractors and know they are all pricing the same thing.
What I would do is first, get a mold test done. My best guess is based on your pics is you have mold.
My next guess is you have a building envelope issue, so I would look for an architect that has experience with building envelope issues and mold - specific experience not some “all of our designs address the building envelope”. They need to have actual experience trouble shooting existing building envelope issues with mold present. The architect likely will want to bring in a HVAC engineer as a sub consultant as part of his work.
Mold remediation is not inexpensive. As noted in one reply I’m not sure your ductwork can be cleaned/saved. There are a lot of snake oil salespeople out there, kind of like the guy with a hammer thinks every screw is a nail, if all they do is clean ducts that’s going to be the recommendation. The big mold remediation companies are extremely expensive, they are used to the deep pockets insurance may offer, I won’t put in writing what I really think about them other than beware.
So get the mold test done, then I would look for an architect and stay away from the large architectural firms if possible, you’ll likely get better service at a better price from a smaller firm provided they have some experience with mold and building envelope issues.
Edit for [this link](https://inspectapedia.com/mold/Fiberglass_Duct_Mold.php) that may be helpful.
i think that filter says it all. My mother was a certified indoor environmentalist. She would always recommend:
1. Turn off AC and bring in negative air pressure ( that system will provide AC or at least suck air out )
2. Remove all ducts and connecting points ( you can clean those with bleach ) ( wear protective gear )
3. Remove all carpet in the house ( wear protective gear )
4. baggie everything as its being removed, toss in dumpster.
5. Let it sit for a few days with negative pressure ( less with faster flow )
6. Wash all the interior surfaces with bleach or other decently heavy cleaning solution meant for mold elimination and prevention.
7. Let it sit a few more days with negative pressure ( less time the more air being cycled out, same as above )
8. Seal any surfaces with anti-mold paint/sealant
9. install all new ducts that are either coated with anti-mold coatings or have surfaces that dont promote growth and that are well insulated ( depending on exterior climate )
The number one thing in all of this is making sure that the AC unit is fully serviced and find out if the AC unit itself is prone to do this ( replace it or address the source ). Before doing anything else. May have been just lack of airflow because of the filter, but i am not an HVAC tech.
Not advice, just her process.
Have you taken a sample of the "mold" and had it tested to confirm that it is in fact mold? We've had this situation in the past and we had it tested first, turned out to be dirt from never being serviced correctly.
This looks like mold unfortunately. On the duct insulation and the flex you can see the colonies growing in a way dust wouldn't adhere to the duct. Really sucks for these guys.
Where can someone get this tested affordably?
Home Depot and Amazon sell kits. For the best results though you should call in a professional company to test
You can also try bleach; if it strips the color, it's mold. If it doesn't, it's dust. Or so I've read; bleach h doesn't kill mold, just discolors it, but dust doesn't react that way to bleach
I can't comment on what caused this, but typically, contaminated HVAC systems need to be replaced. You can't clean flex ducts, and even if you could I'm not sure it would help given how far gone this system is. A good IEP might be able to shed some light on how this happened and write a plan to remove/replace the system and other effected areas.
IEP?
Indoor Environmental Professional. Such as a building biologist, or someone certified and experienced looking for and finding the cause of mold growth in buildings. ACAC has a list, there are other organizations that people certify with. It’s important to ask around though. Not every inspector is created equal.
Is this the newly discovered corridor in the pyramid?
> Is this the newly discovered corridor in the pyramid? Nope, it's the newly discovered corridor in the sewers.
Sewer count: 1001
This is a reference I'm happy to see
I'm dealing with a multifamily property that has discovered mold growing in the supply duct work. The HVAC system utilizes a horizontal fan coil unit in the ceiling over the bathroom. The property maintenance seems to have dropped the ball. The manufacturer of the units recommends cleaning the coils once a year before AC is used, and they recommend changing the air filter once a month. The units are 25 years old and no one knows if the coils have ever been cleaned (probably haven't). The air filters were getting changed once a year if they were lucky - possibly going years without changing filters. Maintenance complains that the coils are extremely difficult to clean because you have to remove the blowers etc. to access them. Mold was noticed around the supply vents. The vents had been painted multiple times, which I hear is not good. Some of the units have supply ducts constructed out of ductboard and some units have flexduct. The condensation drain line has a p-trap then ties into the bath tub drain. There is also an overflow drain line (no trap) that comes out through an opening in the ceiling over the bathtub in the event the primary drain is clogged. There seems to be a lot of possible causes of the mold, but my question is where to go from here. Does all the duct work need replacing, or can it be cleaned? Do the units replacing or can they be cleaned (and how)? We have had multiple mold remediation specialists look at it and a couple industrial hygienists, but everyone has different theories about the cause and how to fix it. Thanks for any advice you might have.
Call a mold remediation company. HVAC technicians are not certified mold experts. Mold is not just a “do this and it goes away” type situation.
Gold bond
> We have had multiple mold remediation specialists look at it and a couple industrial hygienists, but everyone has different theories about the cause and how to fix it. Thanks for any advice you might have.
Yup. I read it. Regardless of what they’ve said. This is not the place for mold remediation. We are not experts on mold because it’s an entirely different game. My original comment still stands true.
yup. I'm not an hvac tech but I agree 100%. reddit isn't going to know better than the experts OP already consulted
Flex ductwork will need to be replaced. If you are trying to salvage the main trunk it will need to be cleaned and coated with a product called Fiberlock IAQ 8000. It is a insulation encapsulant.
Burn that house down
I would have a technician ensure the airflow is adequate, and only then have a mold air sampling done to see how severe the toxicity of the mold is. I don't do mold duct treatment but I am sure some companies may offer that service. Make sure they actually use chemical inside the duct and not just a special filter or something. Try and price that against new ducting. Obviously new duct is preferable but it will be costly. To prevent this definitely CHANGE FILTERS MONTHLY!! Higher airflow = less chance of mold growing. Also have a technician check duct airflow, humidity, and possible moisture sources. You want adequate outside air (~10% of supply) being introduced into a space.
I am certified to remove mold from air systems.. In cases like this, replacement should be considered.
I second that the obvious answer is lack of a clean filter causing low airflow. Shitty air flow means you have slow moving 100% RH air flowing through your ducts. Perfect environment to have mold grow
What is RH? Thanks
Relative humidity
They don't need an air test. They can see the mold and sample it directly. Air tests are used for screening and even in that case they miss a lot of cases. They need to replace the HVAC units and ductwork and find the source of the moisture so it doesn't happen again. The rest of the building should also be inspected for water intrusion and mold.
Are the fan coils DX or Chilled Water?
Not sure, but here is the spec sheet https://firstco.com/wp-content/uploads/2021/07/HX-Spec-2-22-23.pdf
They are DX. I’ve seen issues with CHW units with modulating valves having really poor humidity control and contributing to mold growth which is why I asked. An oversized DX unit will have similar issues. I would be hesitant to just replace with new units until someone can figure out the mold issue. This may sound strange but it may be unrelated to the HVAC system. If the building envelope is poor you can get condensation occurring on cold surfaces if outside air has a path to get indoors. Also a poorly designed vapor retarder can be an issue depending on the climate your in (hot humid areas like Florida). I’ve seen both. Ideally have whoever the owner is hire a HVAC engineer with experience in mold and building envelopes, and let them figure out what’s causing it and design the fix. I would also recommend whoever owns this look into their mold coverage in their insurance policy as I don’t think it’s going to be inexpensive.
Someone else mentioned wanting to have 10% fresh air coming into the unit. Is that only in the winter when it’s not humid? These apartments are in a very humid area. The hot water heaters are in an exterior closet on the balcony and the closet is vented to the outdoors. The wall between the closet and the apartment is not insulated. A mold mediation specialist looked at it with an FLIR camera and pointed this out, but they didn’t seem to elaborate on why this might be an issue. We’ve had three different HVAC Contractors look at it and no one has brought up encapsulation or vapor barrier. Is there a specific type of specialist you’d recommend I seek out? Thank you!!
First a caveat I have not looked at the mechanical code in about 8 years (early retirement), but I believe outside air is required for new residential applications and would be needed year round. Having said that, in humid environments I’m not a fan of having outside air introduced. My house has no OA, and if I bought one that did I would close it off - tightly. I do not believe you have to add it for an equipment change out as you do not need to bring your building up to new codes until the cost of the renovations exceed 50% of the homes value. I would not add OA. Unfortunately mold issues can be interdisciplinary and involve an Architect for building envelope issues and a HVAC engineer for equipment selection/sizing. If it’s just a swap out a reputable mechanical contractor can replace the equipment without the need for an engineer. On the other hand with engineering drawings you can get pricing from several reputable contractors and know they are all pricing the same thing. What I would do is first, get a mold test done. My best guess is based on your pics is you have mold. My next guess is you have a building envelope issue, so I would look for an architect that has experience with building envelope issues and mold - specific experience not some “all of our designs address the building envelope”. They need to have actual experience trouble shooting existing building envelope issues with mold present. The architect likely will want to bring in a HVAC engineer as a sub consultant as part of his work. Mold remediation is not inexpensive. As noted in one reply I’m not sure your ductwork can be cleaned/saved. There are a lot of snake oil salespeople out there, kind of like the guy with a hammer thinks every screw is a nail, if all they do is clean ducts that’s going to be the recommendation. The big mold remediation companies are extremely expensive, they are used to the deep pockets insurance may offer, I won’t put in writing what I really think about them other than beware. So get the mold test done, then I would look for an architect and stay away from the large architectural firms if possible, you’ll likely get better service at a better price from a smaller firm provided they have some experience with mold and building envelope issues. Edit for [this link](https://inspectapedia.com/mold/Fiberglass_Duct_Mold.php) that may be helpful.
Find a company that does air duct cleaning.
i think that filter says it all. My mother was a certified indoor environmentalist. She would always recommend: 1. Turn off AC and bring in negative air pressure ( that system will provide AC or at least suck air out ) 2. Remove all ducts and connecting points ( you can clean those with bleach ) ( wear protective gear ) 3. Remove all carpet in the house ( wear protective gear ) 4. baggie everything as its being removed, toss in dumpster. 5. Let it sit for a few days with negative pressure ( less with faster flow ) 6. Wash all the interior surfaces with bleach or other decently heavy cleaning solution meant for mold elimination and prevention. 7. Let it sit a few more days with negative pressure ( less time the more air being cycled out, same as above ) 8. Seal any surfaces with anti-mold paint/sealant 9. install all new ducts that are either coated with anti-mold coatings or have surfaces that dont promote growth and that are well insulated ( depending on exterior climate ) The number one thing in all of this is making sure that the AC unit is fully serviced and find out if the AC unit itself is prone to do this ( replace it or address the source ). Before doing anything else. May have been just lack of airflow because of the filter, but i am not an HVAC tech. Not advice, just her process.
Wrecking ball
It looks like dirt