If properly sized and installed,the new ac units will help if not totally eliminate the mold.

Take some pictures of it and post them. I'd like to see it.

Mold in the home is typically a moisture problem. The aftermath of a flood, plumbing water leaks, AC condensate that isn't drained properly, operation of an over sized AC that doesn't remove humidity because it can't run long enough due to it's size in relation to the structure.

Anything related to excessive moisture in the home can cause mold to grow and spread.

Hi, Trent,

Sorry for your experience.

Mold/mildew spores are in the air all around us. To get established, mold needs a food source (the paper face of your drywall checks that box) the right relative humidity (60% or higher) and the right temperature range. Once established, it can thrive at a relative humidity below 60%

"the downstairs unit hasnt worked in 2 years and the upstairs one works, but it cant handle cooling/heating up the rooms upstairs on the more extreme days and nights."

If you haven't had an operating air conditioner on the lower level in two years--that means you've had no control over the relative humidity on that level of your home. The 2nd floor unit is currently insufficient for that task, too. You'll need to get the relative humidity levels down below the range which supports mold/mildew growth. I also suggest you look in and around the home for moisture intrusion--a damp crawl space, for example, is often a source of mold that can then be spread throughout your home.

Be aware of adding moisture to your home: always run exhaust fans when showering/using bathroom, cover all boiling water pots, etc.

Your hvac system may need a dehumidifier.

By definition, if the mold keeps coming back, you DON'T have it under control!

IMO, a huge source of condensation that the mold needs to grow in new homes are all those leaky and/or cold sheet metal flex duct connections at junction boxes and ceiling registers. It doesn't matter how good the flex connections are made, exposed cold metal surfaces will condense lots of moisture. Encapsulation with spray foam will go a long way to help this.

To austin air: There was leak in the upstairs above the garage, which was caused by hurricane Florence. The walls in that room had some mold starting grow, but I replaced the bottom 4’ of drywall with new drywall and insulation myself and I haven’t gotten any of the mold in the vents like in the rest of the house. This room is more of an outer reach like I said in the first post. I did post those pictures of what it looked like before I got to cleaning. i am unsure about the part of the ac removing the humidity

To charles ross: I haven’t had the main ac unit working like i said, but I did put a floor ac unit in the master bedroom, downstairs guest bedroom, living room, and office to keep the downstairs cool and I have 1 dehumidifier running in the dining room for the past year along with an air purifier I just got a few weeks ago. Until I get the whole thing replaced, should I get another dehumidifier or what other way could I get the humidity to a proper range? I haven’t thought about the crawlspace, ill put on my jump suit and check that out. I did have a pump installed back in 2007 that’s supposed to pull sitting water from the crawl space, but I haven’t noticed if it still works good or not.

To HU-8####: i guess I was more like putting a band aid on an amputation rather than having it under control.

I have noticed that with the metal. Something else you just reminded me of is this. This is the downstairs ac drain pipe. After it stopped working, mold started to grow everywhere on the other side of the drywall to a point where I just cut out rather than clean it. It was because water was condensing on the outside of the pipe. It took a long time to notice this because this is in the guest bedroom closet and I hardly ever go in there. I ended up turning off the unit from the attic and flipping the breaker for it and That kind of issue hasn’t come back and no water has Condensed since then.

To austin air: There was leak in the upstairs above the garage, which was caused by hurricane Florence. The walls in that room had some mold starting grow, but I replaced the bottom 4’ of drywall with new drywall.

Trent, Yeah that's typically what happens here as well, even the flooring is typically ripped out and replaced as well.

That first picture you show with the chandelier type light fixture hanging from a chain. You see the pattern on the ceiling in that room?

The only way mold grows like that is moisture. What causes moisture? high humidity & cooler air coming in contact with a warmer surface. (They call it dew point)

It's the same thing as taking a plastic cup filled with something cold, the cup will sweat because the ambient air comes in contact with the cool sides of the cup / moisture in the air condenses on the cup. That same effect is what is happening in that room.

If you weren't running the air conditioner, you likely wouldn't have this problem. (I say likely because: you said this house took damage from a Hurricane. Without first hand inspection there are doubts.)

*Typically* --- this is an insulation issue or issues meaning more than one. Mold loves and thrives in damp, dark, cool. It also needs something nutrient wise to grow on... but sheet rock is well designed for that.

During the housing crisis when banks sat on inventory from foreclosures back in 2008/2009. Homes sat vacant... alot of them! You think a bank is going to keep the AC on? LOL. uh- no. --- those homes didn't have any mold at least none that I came in contact with.

So just because it's humid like normal humid --- not hurricane induced humid. Mold will not grow. Damp, dark, cool is where it thrives. When humidity in the home is "off the charts" -- this is where I have my doubts. I've seen some really bad stuff in regards to hurricane / flood damage.

--------------

What to do: Inspect these areas from the attic visually. If insulation isn't filling the void of those rafters from the sheet rock to the top of the rafters that will need to be fixed, but with the growth of this mold like it is, probably best to rip all that sheet rock out.

Once new sheet rock in place --- then insulate as I mention above.

The green room doesn't look as severe to me. It should be investigated and reinsulate above as I said above. Unless this room is a lower level room --- you may be causing the problem with an inoperable AC from upper floor and cooling this room from below that.

Because floors in homes are not insulated between floors. If you catch my drift.

Turn the AC temperature up in the mean time 78 at night / 80 during the day (until you have sheet rock replaced / insulation issues fixed and the other AC unit back online. This will lessen the "cool" that mold thrives in with consideration of these other problems. Run the dehumidifier(s) as much as you want that will help too.

Check your water meter - make sure there are no other things adding to this problem. (shut off all water in the house at all fixtures, go to the water meter --- verfify the meter does not move at all --- if it does you need to investigate why it's moving and fix it. )

"The only way mold grows like that is moisture. What causes moisture? high humidity & cooler air coming in contact with a warmer surface. (They call it dew point)"

Sorry, Ray, I can't let that one pass. You've got the physics exactly backward. 180 degrees out of phase. Wrong-O. Dewpoint is never greater than the air temperature.

Dewpoint is the temperature at which air is fully saturated--i.e., it can't hold any additional moisture. It's also called the saturation point. Condensation occurs when saturated air comes in contact with a surface at a temperature which is below the dewpoint. Warm humid air coming in contact with a colder surface, if you like, but no, not cool air coming in contact with a warm surface.

So the cup with cold water in it... a warm room. The moisture on the side of the cup?

This "condensation" appears within minutes on the side of the cup. Temperature differences from cup to surrounding air?

It's the same difference but sheet rock absorbs the moisture to the point of saturation (spongy or damp if you prefer) --- mold grows under those conditions.

Charles do you own experiments.

Like how does dew form on the grass in the morning? (essentially it's condensation... but why do they call it "dew"?) There's some hints in between the lines....

PS: I never said dewpoint is greater than air temp. You're reading things that aren't there... reading problems again Charles?

What causes moisture? high humidity & cooler air coming in contact with a warmer surface. (They call it dew point)"

Read it, yourself Ray. You've got it backwards. Condensation doesn't occur when cooler air contacts a warmer surface (which would imply the dewpoint being higher than the air temperature.) Condensation on a cup of cold water occurs when warm, humid aid contacts the cooler cup surface-which is below the dew point. You can even check your favorite Wikipedia sources if you like. Or you can ask a fifth grader.

Condensation on drywall occurs when the surface temperature is below the dew point of the surrounding air. Those kind of conditions happen frequently in the south and are sufficient to promote growth of molds/mildews. You don't need a leak or a flood although both will work more rapidly to promote mold/mildew.

Professionals don't get their fundamentals, backwards, Ray. I think you don't understand basic psychrometrics which explains a lot of your illogical posts.

Condensation on a cup of cold water occurs when warm, humid aid contacts the cooler cup surface-which is below the dew point.

Well sure I posted it backwards... because the thread isn't about the cooler cup, it's about mold growth on a "warmer surface" that comes in contact with cooler air. I just used the cooler cup as an "example". LOL.

The OP was running an air conditioner. Cooler air from air conditioning --- in a room with high humid content comes in contact with a warm surface....

It's the same difference Charles?

How do you think dew forms on grass in the morning Charles? The ground is warm, temperature does what at night?

Yes, another common sense thread.... that some how has gotten away from our resident home builder.

"How do you think dew forms on grass in the morning Charles? The ground is warm, temperature does what at night?"

You've still got it backwards, Ray.

Condensation occurs when air is cooled below its dew point. Dew on grass occurs when the air cools to a temperature below its dew point (saturation point.) That's fifth grade science class material.

If a room is conditioned to say, 70 F, the drywall ceiling temperature might be, say, 71 F or 72 F. If air with a dew point higher than 72 F leaks into the room through cracks and crevices around doors and windows, electrical receptacles, switches-- or by flowing backwards though a back vent fan duct connected to the outdoors, you'll get condensation on whatever surface the air contacts (to be clear: the drywall is the cooler, condensing surface.) This is why mold/mildew is often observed when you remove switch plates and receptacle plates. And it's why mold/mildew is often observed around bath vent fans.

You can research weather data for any location on the internet. Every day the dewpoint is higher than the drywall temperature inside the home, there is a risk of condensation.

Back flow through bath vent fans is well documented, and there are a variety of different devices available to minimize the potential for it. The say necessity is the mother of invention. I don't think folks invented the devices if there is no application for them.

You've provided sufficient evidence that you don't understand basic psychrometrics, Ray. For an HVAC "professional" that's a concern. Even more so when the area you service is a hot-humid climate zone. Houzzers will be well served to view your posts with a healthy degree of skepticism.

Condensation occurs when air is cooled below its dew point. Dew on grass occurs when the air cools to a temperature below its dew point (saturation point.) That's fifth grade science class material.

yes, and clearly you are reading things I wrote out of context. I don't disagree with this text above... but things are more complicated when you read and can't understand the context in which it was written.

"How do you think dew forms on grass in the morning Charles? The ground is warm, temperature does what at night?"

what makes up the term temperature above? Is it not air temperature? Are there *not* days in which there is no dew on the grass of a morning?

So there are two temperatures in oposition to one another? aren't there? But yet you say the magical word is "air". If you put room temperature water in cup would it produce condensation? uh, no.

Sorry Charles just a new argument and multiple posts of going around in circles with you.

The problem is: it won't appear like this on sheet rock, until it's much too late *typically*.

There's actually 3 things you need to form what I show in the picture above. Let it be known this is NOT HVAC class. I am here to do it for you, not teach you how to do it.

If you want to learn there are HVAC trade schools across the country. (Charles makes this mistake daily or close to it...)

Ray,

When digging yourself into a hole, it's usually a good idea to put down the shovel.

This one's for you, Charles...

Might be a good time, for both of you to take a break. Seems to happen every time, you both post on a topic. About like my boys, when they were two and three yrs old.

@Trent Pyrtle, mold is extremely difficult/impossible to get rid of aside from removing any and all mold infested materials which is often nearly impossible. Many molds are nearly impossible to kill and can exist in tiny spaces beyond the reach of any chemicals.

I think the best option is to create an environment where the mold is effectively dormant and the only way I know of to acheive that is DRY.

Any sheetrock or insulation material that's EVER had mold s/b removed and tossed.

All structural and other material behind that needs to be left exposed to dry air for a period (weeks, months) until the moisture content is below where mold can be active (12%?). If any is rotted or degraded then it s/b replaced.

Once everything is fully dried out then you can redo the insulation and sheetrock.

You need a good dehumidification system in your home that can maintain low enough humidity (55% or less?) in EVERY space at ALL times.

There are a lot of different types/sizes of mold. I believe MERV-9 is the minimum filter thats effective against many but some require higher MERV ratings. Make sure your HVAC system can handle whatever filter you install. FWIW, we run MERV-13's in our HVAC systems for normal use and install MERV-16's if there is considerable smoke outside.

You likely cannot get rid of the mold spores but you can keep it inactive and reduce spread throughout your house.

Might be a good time, for both of you to take a break. Seems to happen every time, you both post on a topic. About like my boys, when they were two and three yrs old.

Imagine how much fun I could have if I went to a "new construction" board?

Every where you look: nothing but "Builder Grade". LOL.

I think it's funny.... and Charles keeps coming back for more and more and more?

Yeah I question that logic too. (This topic was posted under HVAC / Home Repair / Other -- what kind of new home builder gets involved with that???)

The pictures show mold that go's far beyond that which can be remedied by solutions offered here. Personally I would move to a hotel,sit down and read my HO insurance to see what they say about mold and mildew. Cost of remediation in cases this sever often approach value of home. At minimum I urge to speak with your family doctor and have samples lab tested. Even if it isn't fatal,it will eventualy cause serious allergys or worse.

The pictures show mold that go's far beyond that which can be remedied by solutions offered here.

It's a forum board, there are no solutions on a forum board... just *possible* discussions about them.

You can't do an "in person job" from a forum board.

Contrary to popular folklore myth: I am not a psychic, fortune teller, mind reader or crystal ball reader.