Put a vapor barrier in the crawl space. It needs it, and it may be all that needs to be done. Let us know what the inspector finds..

I would do a thorough inspection of the attic...you just never know...
Do you have drainage issues outdoors?
Does water pond up in your crawl space during a rain event?
Also a.c. units can be notorious for mold sources.....condensate , ductwork in hot locations etc.
All the best. Hope you have good luck with the detective work.
Let us know how you make out...

Looks like the crawl space is the issue. My AC ducts are also dry rotted so we will end up replacing those. I live in Florida thus the crawl space humidity is basically the issue. No standing water, but just a humid environment. Vapor barriers have been recommended, but to be honest there is no way we can afford one. Considered doing it myself, but worried about doing it properly. I would assume an improperly installed vapor barrier will make the situation worse. Additionally, we get hit by a hurricane usually yearly, and although my house has never flooded the neighborhood usually does. Not sure how a vapor barrier will hold up in a hurricane. I spoke with some neighbors and thus far have yet to find anyone with a vapor barrier. I imagine the majority of the neighborhood has crawlspace mold.

Of course I will get the mold remediated, but trying to find less costly solutions (even if short term) besides a vapor barrier. Is there any value in installing a dehumidifier in the crawl space without a vapor barrier? As usual I appreciate all the advice!

Thanks

Marc

Installing a vapor barrier is not expensive. You can do it yourself. Here is a very good video of installation. I have never seen the white plastic they installed, its always been heavy duty clear type of plastic in this area, that is used. https://www.google.com/search?source=hp&ei=5LwzXb2dD8rM_Aa9trqwDw&q=U+tube+video+on+installing+a+vapor+barrier+in+crawl+space&oq=U+tube+video+on+installing+a+vapor+barrier+in+crawl+space&gs_l=psy-ab.3..33i299.1526.14408..17076...0.0..0.258.6993.19j35j4......0....1..gws-wiz.....0..0j0i131j0i10j0i13j0i13i30j0i22i30j33i22i29i30.WSRh1Ej_gko&ved=0ahUKEwi9n4eo68TjAhVKJt8KHT2bDvYQ4dUDCAc&uact=5#kpvalbx=_9rwzXZ-3HJCp_QbSsKqgAQ10

I imagine the majority of the neighborhood has crawlspace mold.

Could be. The idea of living at 72 degrees and 40-50% humidity year round is a modern one.

Fifty or 60 years ago, home air conditioning was still considered a luxury. In the summer, it was hot and humid. Things got moldy from time to time, and you wiped them down with a bleach solution, if and when you noticed it.

No doubt hidden mold and mildew was all around us. Cellars and crawl spaces felt damp and smelled musty. That was just the way it was. Somehow, we survived.

Maybe people are more sensitive to molds today. If so, it could be a reaction to industrial and/or agricultural and/or domestic chemical pollutants around us, but that's just a wild guess.

Or maybe we're just less willing to put up with allergy symptoms that our parents and grandparents considered part of normal living.

I've lived most of my life in older houses with those damp, musty-smelling cellars. Where I live now, the cellar dehumidifier runs day and night all summer long, and barely manages to keep the humidity below 70%. I've never had a mold test done in this house, but I wouldn't be surprised if my numbers were even higher than yours. I'm not dead yet, though. :)

This is not to suggest that you should ignore your situation, far from it. I'm just pondering here, and thinking that if this were, say, 1959, this matter probably wouldn't have even come up.

You'd have your windows wide open every night, to fill the house with cooler night air, which BTW is what the architect who designed your 1921 house expected. He couldn't possibly have foreseen nearly universal air conditioning, and for sure didn't design your house for it. Your indoor air quality would therefore be pretty close to the outdoor air quality.

You also wouldn't have spent much of your life with the news media's breathless and profitable fearmongering over every possible potential household hazard, from asbestos in your floor tiles to bacteria in your dish sponge.

So you might not have allergy problems, and even if you did, it's unlikely that you'd be worrying about mold spores in your house.

Food for thought, perhaps, if not for action. Now I'll bow out of this thread, and get out of the experts' way.

Go on Youtube and look for crawl space encapsulation. There will be lots of videos on what is required and how to do it. It's not rocket science. It's hard, nasty, and dusty work. That's why most people hire companies to do it. But, you can do it yourself. The poly that you are seeing is available on the web. You can buy something very similar at Home Depot or Lowes. It's a question of understanding the goal, the steps needed, and acquiring the right materials. The YouTube videos will help.