Home Healthy Home Reader Q & A: HELP! We Have Moldy HVAC Ducts and a Moldy Crawlspace!

Reader Q & A: HELP! We Have Moldy HVAC Ducts and a Moldy Crawlspace!

by Catherine

Where to Begin, What to Do, and Who to Turn To When Mold in Your Crawlspace and Ductwork is Making You and Your Family Sick.

Today’s post comes directly from some recent communication that I have been having with a reader concerning properly remediating moldy HVAC ducts and a wet and moldy crawlspace. She lives in the humid Southeastern part of the United States and has been going through quite a bit of mold discovery and damage control. She is currently facing trying to correctly remedy the problem without spending her family into a financial hole. I definitely feel for her and want to help her navigate this. Much of what she is going through is similar to what we went through with the mold in our HVAC system—getting sick, linking our sickness to something in our environment, locating mold in our home, trying to determine if and how the mold could be safely removed, and finding the money, appropriate professionals, and mental fortitude to get it done.

The good news is that her questions are ones that I feel very confident in answering. These days, all of this “HVAC stuff” is in my wheelhouse, because during the course of our ordeal, I learned more about Indoor Air Quality (IAQ) and Heating and Air Conditioning Systems than I ever imagined. It’s funny how when your wellbeing hangs in the balance, suddenly learning about anything that could improve or destroy the health of those in your home becomes your new passion. The only problem is that now that I know how things should be done for optimum IAQ, I am angered when I hear others’ stories like ours where poor building practices and HVAC design on the front end from trusted “professionals” in the field have caused a home to harbor mold and other environmental contaminants that have made the occupants extremely sick.

In this reader’s case, as you will see, she trusted that everything was done and constructed correctly. She even took some bad advice on add-ons to her system, like a humidifier, thinking she was doing to right thing. It is only now as she faces remediating her crawlspace, ductwork, and HVAC system, that she has found that many things were initially done with subpar materials (aka builder grade) or with designs that did not mitigate mold or improve air quality, but rather, created excess indoor humidity and caused mold growth to occur.

Here is a summary of some of her emails, so that you can understand what she is dealing with:

(Note: As always, I have eliminated or altered some of the particulars and details to protect her identity.)

Hi Catherine!

First of all, I would just like to thank you for all of the information you share on your blog. My son and I have been struggling with Candida for some time. We live a very holistic lifestyle, and I thought I was keeping my home environmentally safe through my use of natural cleaners, decreased exposure to EMF’s, eating organic foods, etc… Mold was never on my radar!!!

I recently noticed that my hardwood floors were starting to buckle and some interior bathroom walls were sweating. I went out and bought a hygrometer and noticed that I had excessive humidity inside my home. I then decided to have someone check my crawlspace. Low and behold, they found quite a bit of standing water and mold!!

In addition, my HVAC ducts are 22 years old and not sealed the greatest. I guess the mold was traveling throughout my house via the duct system. When I conducted an ERMI test, it showed very high levels of mycotoxins. To fix the issue, I just had my crawlspace fixed by installing a vapor barrier, sump pump, French drains and high-powered fans. I am replacing all supply ducts–they are just going to clean the return air ducts. Do you think cleaning return ducts will be enough?? My supplies had wet insulation inside them as they were insulated on the inside so I knew I had to replace them. (The supply ducts are actually in the crawlspace and return ducts are in the attic.) No visible mold has been noticed inside my house other than a wicker bar stool that was sitting right in front of a supply vent.

We have already started replacing our ductwork with flex duct that is going to be exteriorly verses interiorly insulated. Metal ductwork was going to be double the price!! Also, they are putting in the fresh air UVC lightbulb on evaporator coils and installing an ionizer on my air handler. The ionizer is not supposed to produce any ozone and help to destroy mold and bacteria. I already had a really good carbon filter on my unit, but because my ducts were leaky and moist I guess it didn’t matter. Are you familiar with the blue light bulb for evaporator coils and the ionizing system system???

 Is it possible that I could purchase the SANI fogger and fog the house with Ec3 myself?? I have already had a professional mold company come and walk through my house and tell me everything looks okay even after showing them the ERMI results. I know mycotoxins are very serious.

I also did a nasal swab test. My results showed I had a mild fungal infection with the mold cephalosporin showing up.  I also did extensive detoxing prior to this test for the candida, but now I know that I couldn’t completely heal from candida because we are living in a moldy environment. Do you use the CitriDrops Nasal Spray for fungal infections? What about the Sinus Defense? Do you use it on your children?

 I have read both of the HVAC articles on your site and they are soooo helpful!! Just with I would have known these things when I built my house.  

(Note: For your reference, if you are interested in reading my posts with more detailed HVAC information as well, here are the links: https://moldfreeliving.com/2017/09/28/how-to-spot-a-potential-mold-problem-in-your-hvac-system/ and https://moldfreeliving.com/2018/08/11/building-renovating-to-prevent-mold-and-optimize-indoor-air-quality/)

 Thanks, in advance, for your help and guidance.

After reading this, do you feel like I did? Exasperated by what this reader is going through, but wanting so badly to offer any help or guidance that could make this easier or better? She should truly be commended for being such a phenomenal detective and for really investigating until she was able to find the root of her health issues. She was able to put the excess indoor humidity piece together with the Candida piece and then to start looking at the common culprits for indoor mold, like the crawlspace, ductwork, and HVAC system. Honestly, she has done such an excellent job, even going the extra mile with the ERMI test and the nasal swab. Soon, she will probably be an “expert” and won’t need my advice at all.

But, navigating HVAC issues is complicated. There are so many nuances and factors at play—where your systems are located, where your supplies and returns are located, the size of your home, what materials your ductwork is made of, whether or not your venting system connects to your crawlspace or basement, etc. I am also not physically able to assess her home and situation, so I have to go on what I can discern from reading her descriptions and give my advice solely based upon my limited understanding of how her HVAC system is set up and what is going on. Those limits to my suggestions are why I want to take the time, before I share my response, to give you this added “cheat list” of things to look for that often indicate mold in your HVAC, just in case you are worried that you may be facing a similar situation. This list is by no means exhaustive. It is just a quick way to help you know if further investigation in your HVAC and ductwork should be done:

If you notice any of the following signs, mold may be growing in your HVAC system:

  • There is a strong mildew, musty, or mold smell in your home. This one tops the list, because if it smells like mold, it is mold. PERIOD. Also, if you are still noticing a musty smell AFTER the mold has been removed, you still have a problem. Your home should NOT smell like mold.
  • You see condensation, mold, or discoloration in and around your air ducts, intake vents, and drip pans.
  • You have condensation or sweating on interior walls or windows.
  • There is visible mold growing on the exterior of your furnace.
  • You have consistently high indoor humidity.
  • You have a humidifier attached to your HVAC system.
  • Family members are coughing, sneezing and/or congested.
  • Your eyes, nose or throat are irritated.
  • Your skin has developed rashes.
  • You or other family members are experiencing headaches, nausea, dizziness and/or fatigue.
  • You feel better when you are away from your home or traveling.

Now that you are armed with that list, reading my response to this reader may help you even more, because you can put her situation in perspective. You will also see what she is being guided and told to do by the professionals and constrained to do by her pocketbook, verses what she actually SHOULD do to save her health and her home from mold.

Here is my response:

Thank you so much for writing.

It sounds like you are doing all of the right things. If I were you, I would remove and replace ALL of the ductwork. Flex duct is definitely not the best choice for mold or any other allergens. Make sure that there is ZERO exposed fiberglass insulation inside the ducts. If the air or heat is blowing through the fiberglass and then into your living spaces, you will have even more issues with your health. Also, microscopic, sharp pieces of fiberglass can become airborne and cause tissue damage in your sinuses.  If the fiberglass is harboring mold, then mold and bacteria can grow in your sinuses.

Most contractors have no training when it comes to building materials and the impact they have on the occupants or on the health of a home or building. It is something that needs to change, in my opinion. I realize that the metal ductwork seems so much more expensive, but you have to think about the long game with your home and what choice will bring you the best health. In real duct systems, microbial growth occurs on the dust, not necessarily in contact with the metal.

It is also beneficial to consider the fact that once wet, damaged, or contaminated with mold or anything else, flex duct has to be removed and completely replaced. It cannot be cleaned or dried, like metal ducts can. Flex duct also has a life expectancy, where it breaks down over time and must eventually be replaced. Metal ductwork, once installed, can stand the test of time.

Another disadvantage to flex duct is that the seams sometime leak over time, which could be due to aging tapes or installation error. Duct tape is not approved for any ductwork and foil tape tends not to hold as long as a mastic/cloth tape combination.  These openings created by the connecting tape’s failure to adhere over the life of the duct, creates voids that can expose the cold air supply to warm humid condensation-creating conditions outside the duct. Where there’s moisture, there’s a good chance mold will develop. That’s why the moisture source—whether it’s a leaking pipe, roof or condensation-collecting void in the ductwork connection— must be rectified.

I have a feeling that the sweating you notice on your bathroom walls and the floors buckling has much to do with a combo of your faulty ducts, the water in the crawlspace, and possibly the humidifier that is attached to your HVAC system. The visible moisture is most likely due to condensation, which typically occurs during warm months. When your house is warm, water vapor can begin to form on the inside of your air ducts as cold air is pushed through them. If there is a high level of humidity in the air, the water will begin to collect instead of evaporating. Any environment with high moisture is a breeding ground for mold. What can make an HVAC system particularly bad, especially in terms of harboring mold, is the air it takes in from the outdoors. In your case, this would be the air that sounds like it is taking in through the supplies in the crawlspace as the crawlspace is also vented to the outside. With outside particles continuously being pushed through the ducts, dust collects in them. Dust contains organic materials, such as pollen and skin cells. These substances are the equivalent of food for mold, providing it the opportunity to grow and multiply. Thus, I am happy to hear that your crawlspace is being remediated, dried, sealed, and proper drainage is being employed, so that water does not accumulate there again. This as well as continuous dehumidification will be a key component to remedying the mold in the whole system.

My crawlspace knowledge is not as extensive as my HVAC knowledge, but here is what I know: Isolating your crawlspace is key.  A crawlspace should be isolated from the exterior and dehumidified; otherwise, humid air can enter the space and lead to condensation and mold growth.

Also, there shouldn’t be ANY exposed fiberglass in your crawlspace. Fiberglass in a crawlspace cannot be kept clean or totally dry. Thus, it will eventually be dirty, harbor pests, and/or harbor mold. If your crawlspace has a dirt floor, the dirt should be covered with a vapor barrier to limit the evaporation of moisture from the soil. Air flows from bottom to top, so if you are having any mold problems in your crawlspace, you can be sure that the air inside your home is also being negatively affected. (A helpful article with a section on crawlspaces and sealing venting to crawlspaces can be found HERE.)

Ionizers and UVC lights are more gimmicks than solutions for mold. Ultra-violet (UV) lights are supposedly designed to keep the mechanical system free of microbes. UV light has been used for decades to disinfect air, and does so successfully; however, the pivotal Canadian study that stated that UV lights would improve the health of millions of allergy sufferers was flawed and thus renders the conclusion that inspired the multitude of UV products for HVAC systems somewhat invalid. I won’t bore you with the details, but the main takeaway is that a UV light CANNOT actively clean air flow when installed as a “stick light” inside the return air duct near the air handler coil. This kind of UV light cannot totally dry the coil and could only kill microbes and mold on the coil in the spot where the light is directed.  It also does nothing to filter the air. Thus, while the light could prevent the growth of mold and microbes on the coil, it cannot improve your current air quality or prevent mold from entering your HVAC system when you have leaky ducts and excess moisture. 

Ionizers disperse negatively charged ions, which indirectly creates ozone—I don’t care what anyone tells you. When you stand by a waterfall and the water crashes against the rocks, negative ions and ozone is naturally generated. Outdoors, this cleans the air and makes it smell, well, charged for lack of a better word. The concentration of ozone in an outdoor setting is also not of major concern. But, an ionizer that disperses negatively (and/or positively) charged ions into the air in a concentrated and enclosed setting can generate enough ozone to cause respiratory issues for those living there. Further, these ions attach to particles in the air giving them a negative or positive charge so that the particles may attach to nearby surfaces such as walls, furniture or each other and settle out of the air. Some units also have internal “plates” that help gather the particles, like a filter does. In recent experiments, ionizers were found to be less effective in removing particles of dust, tobacco smoke, pollen or mold spores than either HEPA filters or electrostatic precipitators. Thus, it is my opinion, that if you are going to spend the money, invest in high-quality HEPA filtration instead. Take that for whatever it is worth.

If you do decide to do some sort of air purification system as part of your HVAC, I recommend the Perfect 16 by IQ Air (seriously the best one on the market) or one of Aprilaire’s whole-house purification systems. You also need to make sure you are using pleated filters in your furnace that are MERV 8 or above, so that they can properly filter mold spores and particulates out of your air. Change your filters every 3 months as well.

If you don’t want to invest in whole home purification, consider purchasing portable IQ Airs or other well-regarded HEPA purifiers for bedrooms and your main living space.

To really get to the root of the problem, you have got to address the moisture. Mold is caused by excess moisture and organic material that it can use as food to grow (aka the dust, insulation, and particles in your ducts). Rather than spending money on either the UV light or the ionizer, I highly advise you to invest in a whole house dehumidification system that is linked into your main HVAC system. That way, air is dehumidified at its entrance source to your living spaces. You will also have the added benefit of being able to control and monitor the humidity levels in your entire home from your thermostat. If you keep overall humidity below 50% you will be doing a lot to cut mold off at the pass. Consciously mitigating indoor moisture is one of the single most valuable investments that you can make for your health.

Now to address the mold remediation company seeing your ERMI results and not thinking that mycotoxins are a problem angers me so much.

(Note: Here is the quick and dirty on ERMI testing: An ERMI–Environmental Relative Moldiness Index—test looks for the DNA of 36 molds that are further divided into 2 groups in a vacuum or dust cloth sample that is collected from an indoor space. The vacuum sample is captured by attaching a small plastic tube with a filter inside to the end of a standard vacuum hose. The dust sample is captured by using a sterile cloth called a Swiffer Cloth that is swiped over surfaces. Either sample is sent to a lab that does a mold DNA analysis and sends back an ERMI report. The ERMI report lists the counts for all 36 molds and gives an overall score. The score is the difference of Group I molds—mold most typically found in water-damaged buildings—minus Group II molds—molds typically found outdoors. Based on your score, you should be able to determine whether or not the space is safe to inhabit. As you all probably know by now, I’m not a fan of this way of thinking, because, if a house or building is making you sick, but has an acceptable ERMI score, what then? ERMIs can give a false sense of security to some, and feelings of desperation to others. In my opinion, if you are sick, leave or fix the environment. I don’t care what the ERMI says.) Currently, the mold remediation space is not properly regulated. I could start a remediation company tomorrow, even if I knew nothing about mold. That is why you always need to look for credentials, like IAQ certification, Bau Biology degree, environmental inspector’s or hygienist’s licensing, etc. I actually wrote a post on this topic. You can find it HERE.

As for fogging your home yourself, YES! Yes, you can do that. To do it correctly, you will need to also purchase a certified HEPA vacuum, though. Once all HVAC work is complete and no more construction is occurring, you will need to methodically fog each area of your home and each piece of furniture in your home. Then, move fans into completed areas to ensure air circulation and proper drying. Do not saturate furnishings walls or ceilings with the fog. You just want to cover everything with a blanket of EC3 to, in a sense, smother the mold. Once everything is thoroughly dry, you will need to HEPA vacuum each room and all furnishings thoroughly. This will further clean the air and remove mold spores. I also suggest that you purchase some EC3 or Immunolytics test plates, so that you can test after you do this to make sure you have gotten your mold counts down. A few weeks later, I would test again to make sure that they are still down. Testing periodically will keep you on top of your mold maintenance and will ensure the safety of your home. This may require regularly (once a month) fogging to get things where they need to be for your health to improve.(Note: I am trying to get the lab testing to display on the blog, but there is scientific proof that regular fogging does keep fungal load down.  It takes some time for mold to get a foothold to the degree where it is big enough to release airborne spores. This is temporary, though, and will NOT fix the mold problem until the moisture source is eliminated.)

The news about your nasal swab is not surprising since you have been inhaling the mold in your living environment. Once you get your home cleaned up, treating the fungal infections in your body (nose and digestive system) will be much easier. Until you remove the antigen (mold), though, it will be hard to get rid of the infection long term. Using the CitriDrops Nasal Spray will help as will irrigating with the Nasopure sinus rinse with the CitriDrops Dietary Supplement added. If the mold has colonized in your sinus, though, you may need a physician to irrigate with a prescription antifungal. This can only be determined by a trained physician. I still use CitriDrops Nasal Spray daily and still find it beneficial, because rinsing the nasal passages with an antifungal is the single most effective way to mitigate mold infection risk.

Also, detox and an anti-Candida-specific diet and supplement plan will work a lot better once the environment is improved. To prep your body, there is no reason why you can’t start yourself and your son on the Sinus Defense now. It can only help and will also support future detox. I use Sinus Defense daily as well and so do both of my mold-sensitive children. It is a homeopathic and directly preventative treatment as far as I am concerned. I love the benefits to our immune systems that the transfer factor gives us. HERE is a post on Sinus Defense if you want to read more.

I hope this helps. I know it is so much information to digest. Just take one day at a time and trust your Momma intuition. The financial part is hard, but the future financial repercussions of not fixing things properly and remaining sick are much worse. We have almost recovered financially from our ordeal, and every day that I feel better and more like my old self, I realize that I wouldn’t change any expensive decisions we made to get here.

Take care and good luck with everything. Let me know if you have other questions along the way.



Have you experienced mold in your HVAC system? Did you find this post helpful? Please write to me at catherine@moldfreeliving.com or comment below. Sharing our stories with each other helps us all to learn and to heal.
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