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Thread: Mold in HVAC

  1. #1
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    Mold in HVAC

    I could smell mold coming from my heating and air conditioning vents, so I called in a company to help. The guy came out and found some mold in the pan and said it looked like the water line may have been blocked. He said that he cleaned the coils very thoroughly and also the pan and unblocked the line. And then he recommended that I have a UV light installed between the coils, which I did.

    As background info, I have a genetic susceptibility to mold so that it makes me very sick very quickly, but it also means that I can very accurately smell mold when I am exposed -- way before a normal person could smell it. So if I smell mold, there is definitely mold. The air from the vents smelled better for ONE day only after the tech cleaned them, and then I started to smell the mold again. When I called the company and talked to the technician, he claimed that there is no way there could be any mold — but there is. He said that nothing else could be done. But when I looked online, I noticed that pros on forums said that UV light often doesn’t help because the home bulbs aren’t strong enough, OR the light is too far away (only works within eight inches), OR that one bulb is not enough (some said three to six bulbs per set of coils which I probably couldn’t afford because I could barely afford the $ for the one light). The technician said that mold doesn’t grow anywhere in the HVAC other than the coils and the pan. So I was hoping to get some feedback from the pros to see what they think and could recommend. Can mold grow in other places in the HVAC system? Is it possible that the mold could come back after only 24 hours and with a UV light installed. I had the technician use Concrobium Mold Control, which usually works very well. The rest of my house is completely mold free, but now the vents are spraying it around my house. I would really appreciate any help or advice that you could provide. Thank you so much for your feedback.

    Sincerely,
    Liz
    Last edited by beenthere; 07-14-2013 at 05:31 AM. Reason: Price

  2. #2
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    Quote Originally Posted by LizFromCA View Post
    forums said that UV light often doesn’t help because the home bulbs aren’t strong enough, OR the light is too far away (only works within eight inches), OR that one bulb is not enough (some said three to six bulbs per set of coils which I probably couldn’t afford because I could barely afford the $ for the one light). The technician said that mold doesn’t grow anywhere in the HVAC other than the coils and the pan. So I was hoping to get some feedback from the pros to see what they think and could recommend. Can mold grow in other places in the HVAC system? Is it possible that the mold could come back after only 24 hours and with a UV light installed. I had the technician use Concrobium Mold Control, which usually works very well. The rest of my house is completely mold free, but now the vents are spraying it around my house. I would really appreciate any help or advice that you could provide. Thank you so much for your feedback.

    Sincerely,
    Liz
    Well researched. Consider that your a/c may be wet for endless hours. Molds need extended hours of very high %RH. Operating your blower for several hours everyday to thoroughly dry the system may prevent mold from starting. At the peak heat of the day when occupied or evening hours when the a/c is need for several hour may work for you.
    Also, you must keep the indoor %RH <50%RH to provide dry air to the ducts. Most green grass climates will need supplemental dehumidification do all of this. Also I would suggest fresh filtered air when the home is occupied to pruge any indoor pollutants and renew oxygen. Check out the Ultra-Aire whole house ventilating dehumidifier to optimized the indoor air and reduce indoor moisture to <50%RH. The dehumidifier's dry air is routed through your a/c duct hasten the drying and eliminate potiential for mold growth.
    Also check your a/c supply during operation to assure humidity control during the peak cooling hours.
    Is there a basement/crawlspace involved?
    Regards TB
    Last edited by beenthere; 07-14-2013 at 05:32 AM. Reason: Price in quote
    Bear Rules: Keep our home <50% RH summer, controls mites/mold and very comfortable.
    Provide 60-100 cfm of fresh air when occupied to purge indoor pollutants and keep window dry during cold weather. T-stat setup/setback +8 hrs. saves energy
    Use +Merv 10 air filter. -Don't forget the "Golden Rule"

  3. #3
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    Any insulation that is inside ducting downstream from the cooling coil can be a host for mold to grow. The coil itself can also harbor mold if it is dirty. In your case, being that your tech cleaned the coil and pan, you may have mold active in insulation exposed to the high humidity present near the coil. The UV light can help for the coil and pan, but may not penetrate deep enough into insulation to kill anything embedded there. Solution there would be to get the insulation on the outside of rhe duct, and disinfect the exposed metal once the insulation is removed.
    Psychrometrics: the very foundation of HVAC. A comfort troubleshooter's best friend.

  4. #4
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    Sorry it took so long to respond but this is my first time on a forum and I kept watching the post online, assuming that it would automatically update/refresh when I received a reply but it doesn’t so I didn’t realize I received your feedback until I just checked my email. Thank you Teddy Bear and Shophound so much for responding.

    I have a couple questions regarding your posts. Teddy Bear mentioned humidity. I live in Roseville, CA, which is outside of Sacramento and it is usually dry here. Can the humidity in my house be too high when I live in a dry climate; I assumed it wouldn’t be but I have no idea. There is no crawl space or basement (concrete foundation). Lately it has been very hot, so the air conditioner has been running a lot, but I always run my fan 24/7 even when the air conditioner or heating isn’t on, hoping that will help with air circulation but maybe it doesn’t. You said to run my blower which I assume is the fan, so it does run 24/7. You mentioned supplemental humidity reduction so this is where I wondered if my house could be humid inside with a dry climate outside??? For fresh air, I have been opening my windows up at night from about 9 pm to 1 am and I have also considered a whole house fan. Not sure what you guys think of those. When I’m done with this post, I will research the Ultra-Aire as suggested.

    I have looked at other options such as ionizers that produce oxidizers to clean the air, but came across the following articles which indicate that they might be medically harmful: Free Radicals Are Not Friendly Oxidizers (http://allergyclean.com/news/5.htm) and The Dangerous Hydroxyl Radical (http://www.lef.org/magazine/mag95/95dec2b.htm). Because of these articles and the fact that I have asthma, I have ruled these units out. But I did have an idea tonight. If I put one of these oxidizing purifiers in my attic (are there electrical outlets up there?), is it possible that the unit would purify the coils and pan and the insulation that Shophound mentioned without distributing the oxidizers through the ducts and into my house. I’ve never seen a unit in the attic. Are the coils and pan exposed among the insulation? I’m kind of hoping they are but am assuming that they are enclosed inside the ducts?? The oxidizing purifiers are very effective at killing mold but it’s not good to breathe the oxidizers in so that’s why I thought of putting one in the attic by the coils and pan and insulation but outside of the ducts. Please forgive me if this is a totally ridiculous idea because I have no idea what the setup in the attic looks like. Shophound mentioned that the UV might not reach the nearby insulation but the oxidizing purifier covers 1000 sq feet so it could potentially sanitize the whole attic (because they do sanitize surfaces too) and the insulation if that’s the problem. A technician is coming back on Monday so I will have him look at the insulation and metal on the outside of the ducts as suggested. Sorry this post is so long but my health has been really suffering because of the mold coming from the ducts, so I am desperate to find a solution. And I am open to any other feedback or suggestions. Again, thank you so much for your help.

    Sincerely,
    Liz

  5. #5
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    http://www.wunderground.com/history/...q_statename=NA
    This is your weather history for the last damp time. Keeping a space warm during cool wet weather also help stop mold from growing.

    My point is to be aware of the indoor %RH and maintain <55%RH as much as possible. During brief periods of high indoor %RH, mold will grow. Indoor moisture from occupants builds up unless there is an air change in 4-5 hours.
    24/7 a/c blower operation will reduce the %RH in the ducts. Keeping everything dry is better than uv lites. You should have an indoor %RH meter monitor your home for moisture build up.
    Mechanical fresh air would be good, even from a good bath fan.


    Also be aware that dirt can build up on anything exposed to air currents and look like mold.
    'Regards TB
    Bear Rules: Keep our home <50% RH summer, controls mites/mold and very comfortable.
    Provide 60-100 cfm of fresh air when occupied to purge indoor pollutants and keep window dry during cold weather. T-stat setup/setback +8 hrs. saves energy
    Use +Merv 10 air filter. -Don't forget the "Golden Rule"

  6. #6
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    I will get a humidity monitor as you suggest. Is there one you recommend to homeowners? As background, my house is 2200 sq feet, and one person lives there 24/7. In the winter I keep the heater at 74 degrees with the fan running 24/7, and in the summer I keep the air conditioner at 81-82 degrees with the fan running 24/7. I always use two bath fans for at least one hour whenever I take a shower. Is this good? After I posted last night I looked up humidity in Sacramento and noticed that there are times when it’s more humid than I realized but less than many other places like the South. So in my area, would you still recommend the Ultra-Aire dehumidifier with the ventilator? Even though I’ve tried to take the precautions above, I still have mold now in the AC. It’s not that I see it, but that I can smell it because I am so allergic to mold. Do you believe that installation of the Ultra-Aire dehumidifier and ventilator in my area would get rid of the mold and prevent it from returning??? Is it the best solution, do you think? Thanks for letting me know that the UV light isn’t the best solution. I really appreciate your time and feedback.

  7. #7
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    Quote Originally Posted by LizFromCA View Post
    I will get a humidity monitor as you suggest. Is there one you recommend to homeowners? As background, my house is 2200 sq feet, and one person lives there 24/7. In the winter I keep the heater at 74 degrees with the fan running 24/7, and in the summer I keep the air conditioner at 81-82 degrees with the fan running 24/7. I always use two bath fans for at least one hour whenever I take a shower. Is this good? After I posted last night I looked up humidity in Sacramento and noticed that there are times when it’s more humid than I realized but less than many other places like the South. So in my area, would you still recommend the Ultra-Aire dehumidifier with the ventilator? Even though I’ve tried to take the precautions above, I still have mold now in the AC. It’s not that I see it, but that I can smell it because I am so allergic to mold. Do you believe that installation of the Ultra-Aire dehumidifier and ventilator in my area would get rid of the mold and prevent it from returning??? Is it the best solution, do you think? Thanks for letting me know that the UV light isn’t the best solution. I really appreciate your time and feedback.
    No dehumidifier is needed if you can maintain <50%RH with fresh air ventilation. It depends more on your local weather. You do occasionally have +60^F outdoor dew points. Monitor your indoor %RH. Walmart or Radio Shack have temp/%RH digital meters.
    Regards TB
    Bear Rules: Keep our home <50% RH summer, controls mites/mold and very comfortable.
    Provide 60-100 cfm of fresh air when occupied to purge indoor pollutants and keep window dry during cold weather. T-stat setup/setback +8 hrs. saves energy
    Use +Merv 10 air filter. -Don't forget the "Golden Rule"

  8. #8
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    I will go get a monitor to see what my indoor humidity is like. That’s good news about probably not needing a whole house dehumidifier. When you say “with fresh air ventilation,” are you just referring to opening my windows as much as possible. In the winter it’s usually too cold. I try to open windows some nights in Fall and Spring but not all the time. And in summer, it’s often too hot to open the windows at all; it can be 90 degrees at midnight to 1 am. So do I need an actual fresh air ventilator for the many days that I can’t open my windows to prevent mold, or are you saying that I just need to look at a monitor and open my windows when the indoor humidity is over 50%? Please forgive me if I’m misunderstanding what you’re telling me. Controlling humidity makes sense, but I just need to make sure that I understand the best way to do that. Thank you.

    Cheers,
    Liz

  9. #9
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    Try This:

    Switch the fan to auto. Only run fan when a/c is on.
    Do not operate any other fans.
    Do not open windows at night.
    Shut the bathroom door and open a window (If you can) while taking a shower. Don't use the exhaust fan. I say this because your bath exhaust duct just may be blowing moist air into the attic adding humidity. So this little test will tell.
    Go look outside, find your condensate drain, and see if water is actually coming out.
    Are all your down spouts leading the water AWAY from the home?
    How big is your a/c system?

    Hope this helps!
    Always here

  10. #10
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    This is the Ask Our Pro's forum. In order to post a response here, you must have verified qualifications and have been approved by the AOP Committee. You may ask a question by starting a new thread.

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  11. #11
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    In a dry climate, operating the air handler "on" mode may ok for keeping the ducts dry and also a method of getting fresh air into the home. If you home has returns from the individual rooms, a 6" fresh air inlet on the return side of you air handler ahead of the air filter could be the simplest method of circulating fresh air throughout the home and filtering the fresh air.
    MOnitor you indoor %RH to start off. Occasional 55%RH is ok.
    If your ducts are in the attic, moisture in the ducts during cold weather could grow mold. Recirculating air during cold weather will keep the ducts warm and dry.

    Keep us posted.
    Regards TB
    Bear Rules: Keep our home <50% RH summer, controls mites/mold and very comfortable.
    Provide 60-100 cfm of fresh air when occupied to purge indoor pollutants and keep window dry during cold weather. T-stat setup/setback +8 hrs. saves energy
    Use +Merv 10 air filter. -Don't forget the "Golden Rule"

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    Adlerberts-Protege

    This is the Ask Our Pro's forum. In order to post a response here, you must have verified qualifications and have been approved by the AOP Committee. You may ask a question by starting a new thread.

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  13. #13
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    Thank you Teddy Bear and Energy Star. I got the humidity monitor as you recommended, Teddy Bear. Tonight it has ranged from 35-41 percent, so I will watch it. I am printing out this thread to show to the tech tomorrow and to ask questions. I will get his feedback on the questions that Energy Star posed. Unfortunately, my master bath doesn’t have a door; it vents directly into the master bedroom, so I don’t know if that will mess up the test. Hopefully the tech will be able to tell if the bath exhaust is blowing moisture into the attic. Will also ask about a fresh air inlet. I will get feedback tomorrow and post findings. Thank you so much!

    Cheers,
    Liz

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