At what Humidity % does Mold become a threat?

[Miles]

I am curious.. I have heard multiple opinions.. My Hygrometer says 40-50% is the 'comfort zone', however anything above 60% is dangerous..?

Does any have any links or scientific/person experience with this issue?

 

[Oddball]

A relative humidity of 55% will provide the environment needed for black mold and other fungi to develop. Moisture saturation and material of surfaces determines the extent/rapidity in which molds and fungi will propagate.

 

[Oddball]

I guess I should explain as I was told when figuring the proper dehumidifier for my fish rooms.
Relative humidity (RH) describes the amount of water the air can hold at specific temperatures. A room at 70F with 50% RH will have a RH of 100% when cooled to 50F.
The comfort zone for humans is 30-60% RH. Mold grows best in an RH of 80% and above. Dust mites prefer an RH above 60%.
It's best to maintain an RH of below 50% to prevent wood construction materials from warping and, of course, to deter mold, fungi, and mite growth.
It's been a while since I checked for this info. You could google 'determining relative humidity' and 'adjusting humidity' to get more info.

 

[Miles]

Ahh.. Thanks Phil.

I recently finished the installation of my Air Exchanger and was quite upset to find that over the last 2 days of constant operation, it is holding my Humidity (per digital hygrometer) at around 60%.. This unit was suppose to easily handle 3500sq ft, however the basement area it circulates is only around 1000sqft.

I do have suspicion that it could be do some rainfall here in the Area, as I would imagine the out door humidity would greatly affect the the 'fresh' air being blown into the house..

I only have about 1000g of tanks set up in the basement as of right now, but plan on doubling that before too long. It looks like I will have to keep the digital de-humidifiers around just for pre-cautionary measures.

Any Suggestions?

My house was built in the 50s and the basement has alot of wood panelling in it, which I am afraid the mold would grow behind. I am thinking about installing some small ocellating fans in the ceiling to increase air flow. I once read that if you keep the air in constant movement, the moisture has a hard time 'settling' down into absorbant materials.

Also, the Temprature holds a steady 80 degrees, dont know how much that matters with the RH factoring in..

*Note - I also have a bad 'negative slop' in which rainfall will flow towards the foundation of my house.. I am going to be fixing this soon, but I sure hope this isn't causing any greater problems..

 

[Oddball]

You nailed it with the air movement. My dehumidifier (72 pint unit) grabs alot more moisture when my ceiling fans are on. Makes sense considering heat rises. My ceiling also feels drier with the fans on.
I also installed a heavy duty shelf, near the ceiling, and moved the dehumidifier up off the floor. It works better up high and is out from underfoot. I just "T" into the drain pipe to plumb the dehumidifier from behind a rack of tanks so I don't have to deal with dumping the reservoir.

 

[Oddball]

Ahh.. Thanks Phil.



My house was built in the 50s and the basement has alot of wood panelling in it, which I am afraid the mold would grow behind. I am thinking about installing some small ocellating fans in the ceiling to increase air flow. I once read that if you keep the air in constant movement, the moisture has a hard time 'settling' down into absorbant materials.

*Note - I also have a bad 'negative slop' in which rainfall will flow towards the foundation of my house.. I am going to be fixing this soon, but I sure hope this isn't causing any greater problems..

I painted all surfaces in the fish building then, coated everything with external varathane. Then, sealed all seams (panel, molding, etc.) with transparent weather/window caulk. I had litmus indicators in most of my walls for the last year+ to check for moisture getting behind the paneling. But, none have turned different colors yet.

I don't envy you on the retaining wall project. That's big bucks to get it done right. My brother had the same problem and was able to stop the runoff with curbing fashioned in a slight arc around the front of his house. The outer edges terminated at recessed 8" drain pipes that led to the gully behind his house. If it wasn't for the gully, he would have needed a large dispersion gravel pit at the rear of his yard.

 

[Vitaliy]

I spotted a couple of tiny growth’s which looked like mold to me, I paid this company to do a test for mold and they found black mold in my room. This is what I get for having 100+ gallons in a small NYC bedroom. I ended up sticking huge fans on the windows and constantly have them running now.

 

[Miles]

Yikes!

I my yard is all screwed up anyways, and has lots of awkward slopes. I planned on bringing in a back-hoe, to 'pull back' the negative slop and have the yard sloping in the right direction. At the same time, I plan on installing a sprinkler system as well as planting all new grass.. 3 birds with 1 stone, hopefully.

Thanks for all your input!


Heres another question, a bit off-topic. I was playing with the thought of having the de-humidifier drain back into the fish system. I understand this water is incredibely soft and stripped of hardness, which is beneficial to me because my water is hard and I import soft-water fish.. I have also heard that bad bacterias and other negative properties come with de-humidified water.. What if I were to have the drain flow through a purity system with a layered unit of carbons, resins, and chemi-pure?

 

[Oddball]

I've known people that have tried it, both with and without success. The major restriction is the material making up the dehumidifiers condensing coils. If they're copper, forget it since the copper levels can be lethal to your fish/inverts. If they're made of stainless steel, you can filter it for reclamation. Where I live the water bill is a flat rate for usage no matter what volume I use so, I just sewer the dehumidifier's waste water.
The potential bio-hazard of this waste water isn't bacteria. It's black mold spores and fungi spores. So, part of the reclamation filtration needs to filter down to 5 microns or less.

 

[Oddball]

I spotted a couple of tiny growth?s which looked like mold to me, I paid this company to do a test for mold and they found black mold in my room. This is what I get for having 100+ gallons in a small NYC bedroom. I ended up sticking huge fans on the windows and constantly have them running now.

I have a separate building for my fish. So, I was able to buy an exterior mold inhibitor (aqueous copper sulfate) and painted all my varathaned wall/ceiling surfaces with it. Still have some more prepping and coating to do but, I have way less mold now than I did before I started these surface treatments. I don't know if this treatment is advisable for inside the home.