View Full Version : Mold on grills
07-20-2004, 11:59 PM
Hello - I'm hopeful someone can offer advice. We purchased this house three months ago - it is approx. 60 years old, galvanized/metal duct work was probably installed in the mid 60s. The HVAC unit itself (Carrier A/C - Furnace combo) is probably 3-5 years old and includes a UV light system that is located at the return according to the A/C tech sent by the home warranty company.
Approx. 6 weeks ago we noticed mold growth on the grill in the downstairs bathroom. We returned from one-week vacation at the end of June and mold is now on almost all of the grills although not as bad as what is in the bathroom (temp on A/C was 80 degrees while we were gone if that makes any difference). The A/C tech sent by the home warranty company says that the unit is in fine shape and that he suspected mold in the duct work. The home warranty says such work is considered routine maintenance and is not covered.
We called 2 duct cleaning companies - both reps said we have mold in duct work (neither removed even 1 grill) and offered to clean the duct work for between $700-850 using vacuum/big brush method that is described on EPA/NADCA websites (I apologize for my simplistic terms). Both said they would use Fosters 40-20 on all insulated areas - the first company said they would fog with Fosters 40-80 into clean ducts.
What is a good course of action? What additional questions should I be asking? Is cleaning of ducts necessary?
Thanks for any advice that can be offered!
Catherine in New Orleans
07-21-2004, 08:13 AM
Your house is too cold. Raise the stat a couple degrees.
07-21-2004, 10:40 AM
Grills/ducts are that are wet for more than a couple days grow mold. You live in wet climate. Get %RH meter and track the temperature and %RH. High indoor %RH allows the grills to sweat during the off cycle of the a/c. Less than 50%RH inside decreases the amount of condensate on the grill. Operating your fan in the "on" mode also helps dry the ducts/grill during the none-a/c time. Drying the coil/ducts with the fan unfortunately raises the indoor humidity levels above 50%RH.
One of the solutions to this problem requires a whole house dehumidifier connected to the a/c ducts. The unit circulates dry air throughout the home via the a/c ducts when the home or ducts are wet. Keeping the home <50%RH is very comfortable and allows a warmer indoor air temperature.
This an example of the equipment available.
Several models are avialable from many manufactures.
07-21-2004, 05:39 PM
I know this may be a silly question, but what is a %RH meter? Also, why would Steve say my house is too cold - I would think that 80 degrees in a humid climate might be too warm.
Thanks for the info.
07-22-2004, 10:29 AM
%RH is for "percentage of Relative Humidity", a measurement of air humidity. You can get one at stores like Walmart, it's called hygrometer. It usually measures both temperature and humidity. It's around $20 for a cheapo version.
07-22-2004, 07:34 PM
If your grills are painted, discard them and replace with new ones with a factory finish. Do not paint with Latex paint.
Gone on vacation for a week and temps set at 80 degrees in a humid climate. Without A/C you had no dehumidification so mold grew on painted grills or dirt on the grills.
I believe another failure will be discovered. You will have a large opening in the duct system somewhere . . . possibly at the location where the UV light was installed.
You're fortunate to have rigid ducts, they are easily cleanable.
09-04-2004, 04:08 PM
Remove some of your grilles and look inside of the attached ductwork. If the mold/mildew problem is only on the grilles then cleaning the ducts is not the solution. Mildew growth on the grilles is usually caused from condensation on those grilles. There are several factors that can cause condensation on the grilles and you should be looking for the cause of the condensation problem. Be sure that whoever looks at your system can explain to you what is causing the problem so that you understand exactly what you are dealing with. If they cannot explain properly then keep searching until you find someone who can. BB
11-05-2004, 10:32 PM
Just a thought, like was said air too cold. Like maybe because of a plugged up filter or dirty coil and not moving enough air? or what if the duct is not insulated very well, could it be sweating?
11-14-2004, 11:24 AM
Duct cleaning is not helpful in this situation, or any other for thst mstter, least of all a condensation problem. "Air too cold" makes me scratch my head since we are talking about a/c. Lowering RH is the answer, and the causes can be many. Ask for referrals to a reputable hvac contractor to find the solution. Good luck.
11-14-2004, 08:43 PM
I have a similar situation mold on paited grills and on painted ceilings near air handling unit. Ducts were cleaned and grills replaced. This has made everything great for now until summer comes again. I think the moisture is coming from the ducts sweating, will insulating the ducts correct this problem ???
11-20-2004, 07:17 PM
Does your furnace have a variable speed motor? If so, all that may be needed is a little caulk.
I recommend sealing the gap that MAY exist between the boot of the register & the ceiling. Just an idea that's worked for me in the past....
11-28-2004, 12:58 AM
Did you find a R.H. / Temp. meter at Walmart or HomeDepot? I have one located next to my clock in the bedroom, This way I check at least twice each day. Teddy bear has many post on this subject, you can do a search to find other post too.
12-01-2004, 10:24 PM
Mold is ALIVE it wont just go away mold produces spores. so small that only static electric filters of true hepas can catch them. MILLIONS OF SPORES EVERYWHERE. Mold needs only two things to live water and food allow me to give examples of each:
water: there are up to 110 grains of moisture of water in one pound of 70 degree air (thats a lot when your a spore of mold millionths of an inch in size)infinite. it gets higher the warmer you go (warm air is more humid typicallly.
food:dead skin cells, pollen, dander, drywall dust, smoke reside, oils, fabric particles, ANYTHING that can and does biodegrade is food for mold. these things are so common i duct work and on every surface of your house.
MOOLD CAN KILL new research says that childern with developing lungs 0-14 years that are exposed to certain strains of mold are 120 times more likely to have ashsma and allergies.(do the reaseach your self you dont belive me)
THERE IS HOPE we have to do three things at this point get the spores out or dead , kill the living mold and keep it from coming back
Mold has enimies
I CAN TELL YOU WHAT YOU NEED TO KNOW IF YOU TELL ME THE FOLLOWING:
what kind of furnace ie: where is the filter
which way is air flow
how manny btus of approxamate size of ducts supply and return
size of the house
geographical location so important for humidity
kind of house basment,slab,crawl,
are the grilles painted
where are the grilles located floor walls cellings
How adiment you are about keeping this problem from happening again
How much are you willing to pay to fix it
Please dont be freaked out im not trying to scare you into duct cleaning i just want you to realize that mold can be a VERY SERIOUS PROBLEM thankyou
12-02-2004, 12:12 PM
In response to the previous post:
furnace is located in 2nd story attic - change filter in downstairs hallway
no idea re btus - duct size approx 8 inches metal
round grills are located on ceiling - some have been painted, some have not
we're in New Orleans - obviously a very humid place
house is approx 1800 sq ft
no basement - house is raised on piers
Personally i think that it is a humidity problem - one that existed prior to our purchase of the house. The last owners installed a new furnace with the UV light system about a year prior to selling. One of the companies that came out to provide an estimate noticed a patch on the exposed duct work in the second floor and said it appeared some of that Foster's stuff had been sprayed in that duct work - therefore it seems likely that previous owners had ducts cleaned.
I really appreciate all the advice everyone has provided - thank you.
12-02-2004, 12:20 PM
My mom in Florida swears by Space Gard air filters to reduce dust and mold spores? Would this be worth looking into as well?
12-02-2004, 02:55 PM
spend lots of time reading here, at EPA.gov, etc.
cheapest RH gauge from reptile pet store <$10.
one can tell lots by looking!! all seams & joints need to be sealed with duct mastic. all ducts not in the conditioned space should be insulated with 3" tk, those joints sealed.
12-05-2004, 09:10 AM
I have been doing Mold consulting for over 13 years, work with two of the leading Mycologist in the country (probably the world and can add a few bits of information.)
Everything you have seen posted in reply to your question is true. (though mold itself unless ingested can't kill you directly - you have to have an active allergy to the particular concentration of the exact type of mold growing for that it to cause an allergic reaction. This is documented by over 35 year of date collection by the Mycology Department at the University of Florida and Recent independent studies done by the University of Michigan.)
If the air was turned off during your vacation and the humidity went up, then a mold colony could become apparent.
If the air is too cold on the grill, from low air volume, and it cools the metal to the point of condensation, then a mold colony could become apparent. (a colony is just a term used to describe the area of growth - it can be as small as the point of a straight pin, or as large as a wall). If the paint is organic based the mold could use it for food, if it is non-organic the mold is simply growing on top of it.
The big thing is - Has this caused you or any one in your family health problems? Headaches, excessive tiredness, eye irratation, breathing problems.
If not - the first step is to take a clean (new) sponge put some bleach (cholorine has to be in it) and simple clean the area. The cholorine will kill the mold it touches. If you are sensative to it, use gloves and a nuisance mask (bought at the local hardware store normally used for painting.) See if it goes away - it could be a very local problem. If not them move foward with other actions.
Have the A/C coil cleaned. The drain pan is an excellent place for a source colony.
A good filter can remove lots of mold spores (Space Guard is a good brand, but by no means the only one with that will help.) Keep the filter clean, change it monthly for a while.
If the mold still grows have the ducts cleaned. The mold can't actually grow on the metal duct. There has to be dust present for it to grow on. (the Foster coating is to help prevent dust collection on the internal insulation.)
If the duct is not insulated properly have it done. Improper insulation can allow condensation which the mold needs to grow (Moisture and Organic food source are the two things mold has to have.)
The paint if it is based on a natural substance can be the food source. If after all that the mold grows back and it causes Health problems then change out the grilles.
I have worked on over 350 mold cases. None of them have been completely like another. Each case is a little different and the one thing I will recommend it that you realize that fact. If it doesn't cause immediate health problems don't let any tell you it is going to kill you. That simply isn't true. MOLD is everywhere. Many times the concentration is substantially higher outdoors than it is indoors. (In New Orleans about 6 months out of the year according to air quality indexes kept by the National Weather Service.) So take the most reasonable approach for you and your situation.
If it isn't causing health problems deal with it sequentially. Start at the visible and move outward from there. Start with the most affordable solution and work upward from there.
If it is causing health problems: Find out what is in the air through professional sampling. (Both contact swabs and air compaction testing) But be careful not everyone knows how to properly do this. The safest bet is to use a Certified Industrial Hygenist, or get some one from Tulane who has familiarity with sampling to do it. (I will also offer my services at cost, no profit, no labor, just expenses to come sample it and then have the samples quanititaed and ID). Move the person away from the visible growth areas, and keep them away. Sometimes this means moving to a different room, sometimes to a different building. But again don't let scare tactics make you do anything you don't feel the need to. Reasonableness is the best approach.
12-05-2004, 11:52 AM
bldgcode1 good post:)
12-05-2004, 06:28 PM
I know there are some who have started working with mold in the last three or fours years who disagree but all of the old timers I have met and worked with say the same thing. And it is the most reasonable thing. Least Expensive to most. Visible to unaccesible (not visible)as a standard approach. UNLESS there are immediate health problems which indicate a severe allergy (or asthma). Then you have to a take a more aggresive route.
12-05-2004, 07:07 PM
Yes , thank you bldgcode 1 for being the voice of reason. The majority of posters have been very helpful and I appreciate it.
12-07-2004, 09:54 PM
In Ga A Home owner sued the company that installed thier unit that grew mold and won 546,000 in damages and the condemed her house.
12-07-2004, 10:37 PM
This type of scenerio has played out all over the country over and over again now. (I have personally been involved in 6 cases as an "expert" going both ways.) When you get past the jury trials and into the appeals the awards normally wind up being much lower (the actualy cost of installs, and estimated cost of clean up.) The reason is that juries tend to award big, then the appeals start and the legal fees run up, the insurance companies are the truly deep pockets and keep the litigation going. In one case in TX a 2.5 million house was condemed and the owner, after all the appeals and suits LOST money going to court. Their legal fees exceeded the final award ($210,000). And as the insurance industry steps up active appeals the awards drop down and the legal fees go way up and so do the insurance premimums. Then of course the insurance industry writes exclusions and mold damage is no longer covered.
I am not trying to discourage people who are injuried from taking action, but sometimes one relatively short unforseeable happening can change the entire set of circumstances in an installation. A lot of times everyone benefits if the people involved just do the reasonable thing to start with, instead of fighting over it.
12-08-2004, 12:31 PM
I by no means would pursue legal action. As discussed previously, there are more mold spores in the air in New Orleans than there are in my house!
12-19-2004, 12:23 AM
I understand your problem, I live just south of you in Thibodaux. Everything has pretty much been addressed previously. Check the Heater Vent Light make sure it has a damper and is properly sealed. I see bathroom grilles sweat because the electrician never installed the damper on the HVL all the time.
12-20-2004, 03:27 PM
Also being from a hot-humid climate (Alabama)I often run into cases similiar to yours. I agree with most everything that has been mentioned previously, but would like to take a moment to point out to you a couple of very IMPORTANT things.
#1.) When dealing with mold, SOURCE IDENTIFICATION is the very first thing you should address. Mold on your registers and grilles could very easily be caused by a number of things. One thing that you said that really stands out in my mind is that "the house is 60 years old and on tiers." This tells me a couple of things....Under the first floor of your home is open to everything that Bourbon Street is. The hot,humid air may (depending on the pressure of the home) be being sucked directly through every little crack and crevice into your living area. Ground moisture and relative humidity are things that I would investigate sooner rather than later. If your problem is caused by either ground moisture or ambient air humidity, the most plausible solution would be mold remediation followed by whole house dehumidification. If you control the moisture, mold is not an issue.
#2.) Not to disagree with bldgcode1, but I do think sampling and testing is too often prescribed too early. My point being (and yes I do offer testing and sampling as a service)that if it is suspected to be mold, why do you need to know what the species is? Just get rid of it. If there are some health problems related to this "mold", then testing may be needed. By the way, anybody who walks up to your ductwork and says, "Well, you have a mold problem." Send them on their way. While I can be 95% sure that what I am looking at is mold, there is no way for me to be sure without testing.
That's my .02 cents worth. I hope it was helpful.
12-24-2004, 08:08 AM
I don't contribute very much to this website, but I feel I have to since this is my area of expertise.
Here is what I believe is happening:
1. Your system is probably oversized, this means your AC does not run long enough to remove moisture, but blows very cold air during frequent short cycles. This is causing an extremely high relative humidity level at the area around the supply outlets. Lower tempertures can hold less moisture and as a result when the cold air hits the moist warm air it condenses. Similar to a pitcher of ice water outside in the summer.
2. The UV light in the return duct is a waste of money. Mold spores have to be irradiated with UV light for 2-3 hours before it has any effect. Since they are just blowing by, the light will do nothing unless the mold spore lands on it.
3. As far as mold in the ductwork, mold spores are everywhere. If the house does not smell like a mold farm when you operate the fan, I wouldn't be too concerned about it unless you have some horrible infestation and have severe upper respiratory distress (sneezing, sinus infections, etc.)
4. To fix the problem, the HVAC contractor could increase or add some additional outside air to the return air to increase the run time. Of course the air would have to be conditioned through a desicant and filter first to remove contaminants and moisture. He could also add a reheat loop to increase the heat load, causing the system to run longer. Most HVAC guys know what this is. You could also add a dehumidification system to compensate for the oversized system. Or the most costly of all, replace the system with a properly sized system.
This is a common problem all over the country creatded by improperly sized Cooling systems. Bigger is not better when it comes to humid climates. Best of Luck!
12-26-2004, 04:34 PM
As I read these responces (which are very good) I wonder why no one has mentioned anything about checking to see if the drain on the A coil (located in the duct usually right above the furnace) is working properly, this would be an exellent place for the humidity to begin. Also, is the pan sloped toward the drain.Another train of thought, here in British Columbia the building code requires two four hour periods of exhaust through bathroom type fans,200 cfm or so (which I disagree with) but, the thought is to have at least 1/3 air change per hour, in a 60 year old house this is a piece of cake. If you don't have a pipe coming into your return air duct (before the filter) put one in, if you do make it larger.This will make a slight pressure inside the home forcing air and moisture out. There is only one way to get rid of humidity and that is with ventilation.
If you run your furnace fan continuously you will reduce the temp difference in the duct and reduce the amount of humidity created this way (you need a 23* temp difference to create humidity from the air.)
I hope this is of some help, the cost of these ideas is very minimal. Good luck.
12-27-2004, 10:57 AM
Your not disagreeing with me. My first line of approach is moderation! If you clean up the visible and have no health problems I alwasy say not to do any thing else.
I live in Florida, and have lived in Memphis. Both extremely hot humid areas with loads of mold problems. I seldomly actually sample any growth I find. Most of the time I simply recommend cleaning it up (and of course stopping the moisture that allowed the growth.) Don't ever be afraid of telling some one not to sample. In my personal and professional opinion it is a waste of resources in most cases.
After all how have moldy showers across the south been handled for decades. Dry the shower, spray it with Chorox, and clean it up. (Get rid of the water, kill the mold, abate it!)
01-05-2005, 08:36 AM
FYI, Those cartridges are available elsewhere at 1/2 that cost.
I aggree with alot of what has been said, especially by B-Code. Most of the problems are easily avoidable, by the customer as well as the installer and servicer.
Puling the damn registers off and looking is a good start-simple sealing around where the boot meets the floor/ceiling can help a large number of problems.
I've been in several palatial homes where the customer didn't want to believe they had problem (till it literally exploded in mold). Or they didn't think they should do anything about it once they knew because someone else should be paying for the work.
Our local porn King is sick in the hospital and has the lawyers after the builder, claiming mold is killing him. We all think something else growing somewhere else might be hurting him.
01-06-2005, 09:15 PM
We cleaned the grills with a bleach solution and the mold/mildew/whatever came back. We cleaned a second time and have seen little to no new growth. Now we are occassionally running the heater (we live in New Orleans, what can I say - it was in the 70s yesterday) and have not used the A/C recently (maybe in November sometime) so I tend to agree with some of the posts that we have an indoor moisture problem. We do need to remove the grills but there are soooo many layers of paint that I'll have to repaint after and with three kids that is rather difficult.
Thanks again for all of the advice - y'all are great and we really appreciate your input.
If you have not checked already. I would check between the filter and the equipment for leakage. Here in Houston we commonly find mold growing in the system because warm moist air is allowed to be pulled in from the attic and is overloading the system with moisture. This means that the better, more restrictive filters you use will actually compound your problem.
Smoke is the easiest way to test for return leakage.
"Pigs get fat, Hogs get slaughtered"
01-08-2005, 07:41 PM
Enjoying the warm weather?
I am in Lafayette area now after 15 years of
I wonder if you checked to see if there is a gap
between your a/c box (or boot) and the attic flooring?
This area is often not sealed and often there is a
big gap. Hot air meets cold air and condensation occurs.
So try this .. go into your attic and check one of the a/c
boxes where it rests on the attic floor. If there is a gap
this may be the problem. Or at least it is the least expensive place to start checking.
If you do have this gap there is an excellent product called Hardcast Mastic Tape which is available at HVAC supply for about $25. a roll. This is a tested and approved tape to seal areas like this as this tape will not
only stand extreme attic temps, but it will last unlike duct tapes. It is easy to apply and will seal both to
metal a/c box and to attic flooring material, both surfaces need to be clean and dry.
Best of luck and post when you have time to check and see if boxes are sealed.
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