Mold in Basement

[Bushwacker7]

Over the weekend I discovered black mold in my unfinished basement ( 6 yr old house) growing between the fiberglass insulation and the visqueen vapor barrier. I'm not sure what the problem is. I am from a climate that has a dry climate and mold problems are rare.

Is it possible that the visqueen trapped moisture in the air behind it allowing mold to grow?

If so, would replacing the insulation and (vapor barrier ??!??) and keeping a dehumidifier running likely cure the problem in the future? Do most people find it necessary to run a dehumidifier in the basement to prevent a mold problem from initiating?

Is this visqueen/vapor barrier needed or advisable?

Any thoughts or anecdotal advice is greatly appreciated - Thanks

[BoxMN]

There were a bunch of threads similar to this, so maybe do a search to see them all. Good info in them.

We have new construction a few years ago (I am not a builder, just interested in how its done so asked contractor lots of questions). For our basement (walkout) on the blocks he used Thermax (can't recall exact name) but the double foil sandwiching foam. He put that right against the block, and taped it all up with foil tape. That serves as the insulation AND vapor barrier. He told if I finish it myself, to just add studwall on inside of that and do NOT add any more insulation or poly.

Mine is still unfinished but that seems the norm. I asked him about my home, which is block and unfinished and he told me to do the same thing. Key is taping it all up and not adding more insulation. Somethign about leaving the concrete/block able to breathe but keeping that on OUTSIDE of the insulation.

Good luck, more here are contractors and builders, and can give you accurate expert advice, mine is just anecdotal.

[amateurfishing]

I am in middle of roughing in my unfinished walkout basement as we speak & BoxMN is correct

I have black spots (thinking mold)behind my poly vapor barrier on east & south facing walls. So i took black marker/pen/pencil & outlines some significant patchs. did not grow over time. still concerned b4 finishing basement, i called in city inspector and made phone calls to couple other pros. mold was ruled out for me, the dark spots are just signs of air movement behind my vapor barrier, dirt naturally moves in air & can just get stuck in insulation or on plastic as air current moves behind it. I was told it would stop once drywall is up.

reason i am telling all of this is this may be what u have. highly possible. cut small holes in poly (that u can tape up or cover later) & see if just dirt or if there is a smell. i was told it happens when basements are not finished within certain time frames of home being built (do not know what that time frame is)

get a pro or 2 out & verify if it is actual mold or not. i just had a local building inspector come out after i applied for permit to do a pre check walk through and asked about it then, was told dont worry, its nothing just cover it up.

[soldoncass]

Can you post a picture or two? 6 + years ago it was code to put poly on the inside of blocks, frame wall, put r-11 fiberglass in studs, then poly again on the inside. There was a LOT of problems with that method, so they finally changed codes to foilfaced foam board glued to blocks, and sealed with tape (as mentioned above). Frame the 2x4 wall inside that, add NO more insulation or poly. WALA problems went away.

[Tom7227]

I am sort of simple minded. How do you know that 'WALA the problems went away' if there is a completed wall and insulation that is glued to the wall? Do people tear things apart to see if there is mold? Just wondering.

[JeffB]

I had some issues on a house recently that the basement always had a musty smell and you could see some mold on the insulation. I pulled everything out and had the basement spray foamed. The project turned out great and the smell is totally gone. Your whole layer of insulation is impervious to water and adds a lot of strength to your foundation. If I remember the cost of doing the whole basement was around $2500-$2700.

[EBass]

Got any pics of that foamed basement? Sounds interesting.

[frazwood]

I'm not saying that it isn't possible (perhaps you left something out of your description), but mold won't normally grow on fiberglass and plastic. It needs, in addition to water, a source of organic material. Normally, this organic material can come from the paper used in drywall.

More likely, and other people have said this above, you have air movement through your insulation. Because air contains dirt, this dirt accumulates in the fiberglass, leaving it looking black (kind of like mold).

I agree with everyone above... please post photos.

Other questions: does it smell moldy? Is it wet behind the plastic?

[efgh]

If you have mold on studs and on the block wall, you can paint the area of mold, after scraping it down, with a product called Kills. this is supose to kill the mold spore.

[soldoncass]

Tom,

The problems went away, because the "cause" was no longer present. Two layers of poly traps moisture in between the layers. In some houses , with the old method, there was so much moisture forming on the poly/ insulation it was sopping wet on the bottom. The new method, with foam, we never had a single problem. There are many opinions/ theories about why, I won't get into them.

[Bushwacker7]

I got all the old insulation out today. It did have mold spots on it - but very little. It looked worse with the poly on it - which may have had a film of mold on it ? I kinda felt foolish throwing some of that insulation away. I sprayed everything down and I will let it dry out.

I plan on putting the insulation with the paper surface on one side toward the inside. I may put drywall on it if it's not too expensive. I bought a dehumidifier and plan on keeping that going.

The only side of the basement that seems to have been with mold is the side without the block wall (with the plastic siding). I'm sure that has something to do with it but haven't figured it out yet.

[Bushwacker7]

I agree - it had to be mold growing on dirt spots. It was completely dry and there was no mold on the studs or sheeting behind.

The gentleman that came to look at it said that this problem occurs more with newer houses that are "wrapped tight" in order to be "energy efficient".

[frazwood]

I agree - it had to be mold growing on dirt spots. It was completely dry and there was no mold on the studs or sheeting behind.

The gentleman that came to look at it said that this problem occurs more with newer houses that are "wrapped tight" in order to be "energy efficient".

Again, I'm just guessing because I haven't seen it... but this sounds like dirt, not mold. The fact that it was completely dry is a good thing and indicates dirt, not mold.

[chad austin]

I plan on putting the insulation with the paper surface on one side toward the inside.

[Bushwacker7]

It appears that there is a plastic material on the outside of the sheeting (the sheeting material visible under the insulation from the inside). It feels like it has a texture to it - not like plain plastic. I can see staples in it - so it blowing rain gets in there and through a staple hole, I suppose mold could grow between the wrap and the sheeting.

?

[K_Josh87]

that should be typical install on the house wrap. I'd only expect issues from it being lapped the wrong way, or seams not tapped etc...