Results 1 to 12 of 12
  1. #1

    Help! Mold found on A/C register

    I recently purchased a home and shortly after moving in I noticed a small amount of mold coming out of an a/c vent. When I opened it I found mold on the insulation in the ac register. The mold does not appear to be going into the ducts. What is the best way to clean this and is it toxic? If I rub at the mold will it ruin the insulation? Should I get my air ducts cleaned, and will an air duct cleaning service remove this mold? I posted pictures of one that looked bad in the house and another that looked more normal.

    Thanks in advanced!
    Attached Images Attached Images    

  2. #2
    Join Date
    May 2005
    Location
    Lubbock Texas
    Posts
    773
    Do not agitate it or you will release the spores to spread. Spray it with a 50/50 Bleach concentration and water. Mold spores are common with every day life. You will never be rid of them. As long as moisture isn't present it is harmless unless you agitate it and help them spread. Talk to your HVAC Contractor and see if you can up grade your filtration in your furnace to a Merv 10 rated filter or higher and get a humidistat and monitor your humidity in the home. If you are regularly above 55% you might want to think about a dehumidifier for the home. There are others on this forum that direct you in the right direction for de-humidification applications.
    The premise of ventilation is that the OA is clean or of sufficient quality to be used for dilution. Traditional ventilation is somewhat being threatened by the fact that the EPA is changing the requirements for outdoor air quality which is creating non-attainment zones in what is now becoming a significant portion of the country. That means that buildings in those areas will need to clean up the OA before they bring it into the building.
    www.genesisair.com
    Genesis Air Inc.

  3. #3
    Thanks for the reply genesis. I found that if I take a knife and cut the top layer of the insulation off, the mold is not present underneath. I considered spraying the insulation, but was worried the bleach would penetrate the insulation and make it worse by adding moisture.

    Does anyone know how the mold could just be on the register box and not in the duct work? We don't know what the source of the moisture is and/or history of the house. We opened 14 vents in the house and only 4 look bad like the two pictures on the left and the other 10 look as if they are just old and dirty. Should we get mold test sampling or a mold remediation crew in?

  4. #4
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
    Posts
    6,334
    Follow EPA's recommendations for cleaning. Soap and water, wipe dry. Do not cut plastic in the ducts. Mold spores are everywhere and any continually moist surface will grow mold in the dust that collects. Monitor the indoor %RH. What region do you live in? <50%RH is nice in a home.
    Do not get hyper start cutting. 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"

  5. #5
    Thanks for the response teddy bear. I live in Houston so it gets very hot and humid. Since the post, we're planning on getting the mold tested and will get thermal imaging done on the house to check that it's only where we see it (not cheap). Then we plan on getting a mold remediation company to come out for the cleanup which includes deep cleaning of both the ac units and all the ducts (really not cheap). The guy recommended removing the register box insulation all together, since insulation in the box is a breeding ground for mold. Do you think we're going over board? For peace of mind we'd like to get it all taken care of.

    Another option would be to not test the mold and remove the insulation our selves, then just get a normal duct cleaning. This would be 1/3 to 1/2 the price of the option above.

    ps what's the golden rule?

  6. #6
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
    Posts
    6,334
    You are going of the deep end.
    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"

  7. #7
    Join Date
    Mar 2005
    Posts
    997
    Why test it! You see it so you know it is there. Spend the money to clean it up! Any good HVAC cleaning company can handel this for under a grand. Have both HVAC systems cleaned and treated with BBJ then coat the boxes with Foster 40-20.

  8. #8
    Join Date
    Apr 2010
    Posts
    17
    I have been working for service master a while now and every house has had mold somewhere in it. The reasons can be from a wide variety, like if it is next to a window, or how far the register is from the system and on and on. We use a sanitizer/deoderizer on vents, and a fogger that goes thru all the ducts. It can get expensive depending on how many systems you have, which is about $400 a system and includes 12 vents. But I would make sure whoever you use has a vacuum with the roto brush for the ducts, some people are using a brush connected to a drill that I dont think will work half as good. Good luck

  9. #9
    Join Date
    Aug 2003
    Posts
    906
    It's pointless to clean unless you've changed the conditions so mold won't regrow. IMO making the mold go dormant is the most important, then remove if necessary.
    -If you won't turn it on then nothing else matters.

  10. #10
    Join Date
    Jan 2001
    Posts
    7,698
    Every time I have ever encountered mold....or lets just say..."growth of a substance on air registers.... it has been due to poor airflow. Usually clogged filters...

    Id have the ac system checked and have the registers cleaned....by yourself or the ac guy...with bleach.

  11. #11
    Join Date
    Mar 2005
    Posts
    997
    Dormant mold is an allergen so you need to remove it completely. Spraying bleach on mold by a professional is asking for a lawsuit. A home owner is fine but stick to the products that are EPA approved for use inside of HVAC systems

  12. #12
    Just wanted to update everyone. Thanks for all the suggestions and tips. We've had an all around service to get the whole system cleaned. We got all our ducts cleaned and both a/c units. The technicians said it looked like they've never been cleaned (15 year old house). We also had them rip out the insulation from all the ac register boxes and clean the vents. Some insulation in the boxes that looked mold free from the surface actually had mold on the other side of the insulation, away from view. They treated all the metal boxes and vents with chemicals to prevent mold.

    Now looking at the register boxes with the insulation removed, we have figured out why mold has grown. Let me explain, think of an ac register box as a square, with 4 sides and a top and a bottom. There is metal on the 4 sides. The bottom is where the vent attaches and is what is seen when in the room. The top is where the duct connects to the box. The top should be metal with a hole for the duct to come through, but in this house all the boxes did not have metal on the top, but just a thin layer of insulation. Therefore, attic air is on one side of the insulation and then ac air is on the other, thus producing mold.

    We're currently asking around for ways to add the metal on the top (with a hole for the duct) so the box is sealed, or quotes on replacing the boxes. Anyone have any ideas? or any number on how much it should cost for one box to be replaced?

    Thanks!

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
Comfortech Show Promo Image

Related Forums

Plumbing Talks | Contractor Magazine
Forums | Electrical Construction & Maintenance (EC&M) Magazine
Comfortech365 Virtual Event