Mold in ductwork

[teddy bear]

Mold spores are everywhere. Your a/c cooling coil is a moisture source that may keep your ducts wet enough to grow mold during the cooling season. During the heating season, ducts in an attic could be cool enough to have condensation on inside of the cold ducts.
During the cooling season, operating the fan enough to dryout the coil and ducts for several hours a day reduces the potiental for mold growth. During the heating season, operating the fan enough to keep the ducts in the attic warm enough to thoroughly warm/dry the ducts for several hours every day will prevent mold growth. Mold spore in a damp space for a couple days grows mold. Several hours of high humidity followed with several hours of being dry will not grow mold. Operating the blower continuously will also keep the ducts dry. How about a small amount of fresh air to purge odors/pollutants. Check out a ventilating dehumidifier like Ultra-Aire/Honeywell/Rheem connected to the air handler as an alternative method of dry, fresh air. Regards TB

[Beauble]

That may be. The "p trap" is a preformed PVC dip in a horizontal run of drain piping in the crawl space, not up near the unit in the attic. Not like any P trap I've ever run across.

Doing more research on air purifiers last night. Are the PCO and PHI technologies the same. The descriptions sure sound similar. (Air Oasis, RGF-PHI)

[Beauble]

Mold spores are everywhere. Your a/c cooling coil is a moisture source that may keep your ducts wet enough to grow mold during the cooling season. During the heating season, ducts in an attic could be cool enough to have condensation on inside of the cold ducts.
During the cooling season, operating the fan enough to dryout the coil and ducts for several hours a day reduces the potiental for mold growth. During the heating season, operating the fan enough to keep the ducts in the attic warm enough to thoroughly warm/dry the ducts for several hours every day will prevent mold growth. Mold spore in a damp space for a couple days grows mold. Several hours of high humidity followed with several hours of being dry will not grow mold. Operating the blower continuously will also keep the ducts dry. How about a small amount of fresh air to purge odors/pollutants. Check out a ventilating dehumidifier like Ultra-Aire/Honeywell/Rheem connected to the air handler as an alternative method of dry, fresh air. Regards TB

Thanks. When my house was built 2" insulation wrap was the code. Now 3" is code. Would that help the situation?

[Sleuth]

We need that p-trap right, within a foot or so of the air handler.

Soft corner "preformed" not acceptable.


Your a/c should make somewhere near a quart of water an hour during cooling season. 12 hour run maybe 3-4 gallons +/- .



I hope this helps.

[Beauble]

We need that p-trap right, within a foot or so of the air handler.

Soft corner "preformed" not acceptable.


Your a/c should make somewhere near a quart of water an hour during cooling season. 12 hour run maybe 3-4 gallons +/- .



I hope this helps.

Thanks for all your time . I will certainly get that fixed.

[Sleuth]

Thanks for all your time . I will certainly get that fixed.

This could well be the primary souce of mold in your duct work.

This is the time of year when the mold hybernates/or dies off and outgases causing people who are allergic to complain. I do hope there is not a humidifier in the HVAC system as this could also complicate your situation.

This type(s) of mold is pretty aggressive in temperature between 55-75 degrees F. A/C season.

Gas furnaces will kill off rather quickly or shorten the allergic reaction times. It's still present just dormant. Then the next a/c season it flares up again.
Spring and Fall are the most severe times.

Your results may vary.


Regards.

[Beauble]

That sounds like us. As far as cleaning the ducts, as I read the PCO and PHI air purifier technology, it sounds like they may send "oxidation molecules" (I'm no chemist or biologist) through the duct and clean it up over time. I just have a hard time believing that a mechanical cleaning process (rotary air blast or brush) can clean mold particles less than 1 micron in size. Seems to me that either a mist, or the PCO / PHI technology or a UV light passed slowly through the duct would be required to achieve a kill rate in the high 90s. Know of any resources on cleaning ducts?

[fcs]

GO to ASHARE's http://www.ashrae.org/ site or google ASHRAE MOLD IAQ.
sounds like you have a background that you'll enjoy the site.

Are you a member of AFE or ASHARE

[Sleuth]

To the OP:

Lets get the source under control first.

The evaporator may need to be professionally cut out and cleaned. The plenum/equip and duct probably need to be inspected by a pro to determine the extent and course to pursue.

This has all been building for some time so go outside and take a deep breath, as this scenario is all too common.

Anyone working "in" the system should be wearing a N95 respirator (or better)




Keeping the system temp up and the fan on, these symptoms will fade.

Remember this: asbestos can make you sick in 20 years,
mold can make you sick tomorrow.

Hope this helps you.

[Beauble]

GO to ASHARE's http://www.ashrae.org/ site or google ASHRAE MOLD IAQ.
sounds like you have a background that you'll enjoy the site.

Are you a member of AFE or ASHARE

will do.
not since I was in college in 1977.

[fcs]

will do.
not since I was in college in 1977.

AFE was AIPE back then my father was founding President of the Ft Waney IN Chapter 1n in think 1970 or 71.

[drk]

A good duct cleaning company should be able to get 98 to 99 percent of dirt and mold out of your system. Air purifiers or UV will not be able to handle the job inside of the duct.

[Beauble]

A good duct cleaning company should be able to get 98 to 99 percent of dirt and mold out of your system. Air purifiers or UV will not be able to handle the job inside of the duct.

Once is is cleaned should they be able to maintain it for the long haul?

[drk]

UV will only be able to kill mold it shines on. A media filter would be best. It will help keep dirt out of your system which is a food source for the mold.

[Beauble]

I think I have a plan. I ran across a company called Guardian Preservation using Service Magic (5 stars). No complaints with Chicago BBB. They use a proprietary enzyme to mist through the house and kill the mold. The enzyme eats the mold down to the root, then dies. The MSDS looks pretty harmless for humans and the kill report from the lab is pretty impressive. They provide a clearance letter for the life of the house that is transferable. Still researching them to confirm this technology. I have a friend who is a microbiologist.

If any of you are interested in signing up as a contractor, they are looking for people across the country.

I still need to select a PCO or PHI treatment system for on-going mold prevention - just in case. Any thoughts? I leaning towards the RGF Guardian or the Air Oasis 9" Induct unit. Are there others of similar technology and performance?

[drk]

Can you tell us more about this proprietary enzyme. Is it EPA approved?

[Beauble]

Can you tell us more about this proprietary enzyme. Is it EPA approved?

They say it is in process. Best I can say is go to Guardian Preservation & check it out. I don't want to pitch for them. It just looks like a potential alternative to conventional treatment measures.

[energy_rater_La]

When you opened the duct in the attic, did you detach it from the plenum?
If so was the insulation in the plenum also moldy?
Being in a similar climate, we have dealt with mold fairly often.
High humidity combined with ducts in the hottest part of the attic
should only lead to condensation and mold on the outside of the unit,
plenum and ducts. But..if the ducts are not mastic sealed, and there are
air leaks in to the plenum either at supply or return side then the attic
temps condensate and moisture is pulled into the ducts and plenums.
Once the moisture gets inside mold grows.
I'm not a big fan of duct cleaning, or UV lights for that matter.
What has worked for me is to replace the flex, and sometimes the insulation
inside the plenums (on one memorable occasion..both supply and return plenums)
and mastic seal everything.
Most duct systems have 20 to 30% duct leakage, so sealing the ducts and plenums
increases the system's performance. And once a system is sealed..contaminants
can't get into the ducts.
In my experience, a sealed duct system is a clean duct system.
I use a blower door turned around to blow (pressurize instead of depressurize)
to find all duct leakge. You can do a quasi pressurization test by simply
feeling around heating system to plenum (s) and plenums to duct take offs when
system is running. You won't pinpoint everything a duct blaster or blower door will find, but it will give you a general idea of where it leaks.
Do you have ceiling returns, or is your return air located lower on the wall in a chase?

Keep in mind that even if you kill the mold, it will come back unless you determine what
is allowing it to grow.

best of luck.

[Beauble]

When you opened the duct in the attic, did you detach it from the plenum?
If so was the insulation in the plenum also moldy?
Being in a similar climate, we have dealt with mold fairly often.
High humidity combined with ducts in the hottest part of the attic
should only lead to condensation and mold on the outside of the unit,
plenum and ducts. But..if the ducts are not mastic sealed, and there are
air leaks in to the plenum either at supply or return side then the attic
temps condensate and moisture is pulled into the ducts and plenums.
Once the moisture gets inside mold grows.
I'm not a big fan of duct cleaning, or UV lights for that matter.
What has worked for me is to replace the flex, and sometimes the insulation
inside the plenums (on one memorable occasion..both supply and return plenums)
and mastic seal everything.
Most duct systems have 20 to 30% duct leakage, so sealing the ducts and plenums
increases the system's performance. And once a system is sealed..contaminants
can't get into the ducts.
In my experience, a sealed duct system is a clean duct system.
I use a blower door turned around to blow (pressurize instead of depressurize)
to find all duct leakge. You can do a quasi pressurization test by simply
feeling around heating system to plenum (s) and plenums to duct take offs when
system is running. You won't pinpoint everything a duct blaster or blower door will find, but it will give you a general idea of where it leaks.
Do you have ceiling returns, or is your return air located lower on the wall in a chase?

Keep in mind that even if you kill the mold, it will come back unless you determine what
is allowing it to grow.

best of luck.

I had already pulled out the plenum duct insulation and replaced it with armaflex. I do believe there is leakage. The duct is run from the ceiling registers back to the take-off. There is a flex piece of duct at the take-off. This means that the pressure in the system will try to drive air out of the joints. The take-off had mastic, but I'm not sure about joints in the run. When I replace the flex, I may just take the straight run to the register and flip it end for end to get the joints right. There are two return grilles, one in each hallway. House is pretty much in thirds - master BR / bath, study / kitchen, DR,LR / 3 BR and bath.

[ChuckHVAC]

In my opinion and experience you will not gain much mold prevention with PCO. PCO is a UV light shining on a titanium dioxide grid, it oxidizes what touches the grid. It works great to oxidize odors and even VOCs, but you need to eliminate the source. I have had good results cleaning the ducts, and installing UV lights where they shine directly on the coil. Of course humidity needs to be keep in an acceptable range.