Possible Mold in basement?

[lindy rig]

I moved into a 10 year old house this summer, unfinished basement. I first noticed some dripping water from a fresh air intake in the basement. (dripping from a low point that had previously been duct taped) This was during the hottest part of the summer with our AC cranked because we were doing hardwood floors upstairs.

Asked around and even had an HVAC guy come out. Said they didn't know why water was in there. Kind of dismissed it for excessive condensation as we were running the AC constant.

The other day I noticed what appeared to be some mold in the insulation in the wall behind the plastic vapor barrier.

I've climbed around and peaked behind some of the plastic and it does look like mold only in an isolated area. But everything seems bone dry around it and I can't see any water damage anywhere.

We are running a dehumidifier and it fills a bucket almost daily.

Any ideas what I should do / check to make sure we don't have a problem starting?

[nobody05]

sounds to me that you have an incredibily high humidity problem in the house (obiously) you ever notice water or wet block? sump pump still running or has that stopped? Do you crank the t-stat in wide differations through the day or week in the hot heat?

[CAMAN]

You don't happen to have a humidifier installed do you?

With the patch of moldy insulation, the vapor barrier doesn't happen to have any cuts or gaps in that area does it?

[Tom7227]

Given the lack of rain and the low humidity for the past couple of months I wonder what is causing the high humidity in the basement. A possible culprit could be a leaky exhaust on a dryer, or water heater. Check and make sure that's not what is causing it and if so get it fixed asap.

This is a long shot but is the basement open to the rest of the house? If there is no way to close it off then possibly the coldest air is dropping down there when you have the AC on and the moisture is condensing on the cold air intake because of that.

I would spend more effort on the humidity issue than a bit of mold. I think folks go a little nutso with the mold. I know, don't start on that issue.

[lindy rig]

It's a walkout rambler home.

The sump basket is bone dry and I have not noticed any water inside of it, there isn't even a pump. The backyard slopes down away from the house towards a small pond.

There are cuts and gaps on the vapor barrier (mostly small ones), including one that I recently cut to inspect it. I thought if anything that would allow air inside to help dry it out. After the rain last weekend, I felt the insulation and it did feel damp although again I could not find any water entry from the exterior.

There is a door to the basement. Sometimes we have it open and sometimes closed, but we haven't run the AC now for almost a month. If it was a leaky exhaust on the dryer, wouldn't I smell fumes?

[lindy rig]

There is a humidifier and air exchanger installed in the house. Both have been turned off. I was told to only run those in the winter.

[frazwood]

Finding the cause of water problems in the basement can be very complicated because there are a number of possible causes (and you could have more than one problem at the same time!). This is probably a situation that warrants hiring a professional to come out and take a look (i.e., going to the internet for help is not likely to solve your problem).

The issue with the holes in the vapor barrier is a problem only in the winter. If you have a cold surface next to warm, moist air... you get condensation inside the wall and you get mold. The vapor barrier is designed to keep your warm inside air from meeting the cold exterior wall (the insulation doesn't prevent air movement sufficiently by itself). You won't really see this in the summer because it's not cold enough (usually). This is a likely cause of the mold inside the insulation. The solution is easy enough... remove the moldy insulation, replace the insulation, and replace the vapor barrier (doing so without any holes in it... you can tape over any existing holes but be sure to buy the right tape).

It also seems as if your basement is incredibly humid. We have had this problem at our lake cabin until recently. We had problems with our grading and our gutters, but it took fixing those problems PLUS adding a 3-ft wide sidewalk (with 4-mil poly underneath to prevent water from percolating under it) on one side of the house to solve our humidity problem (this also cleared up a bad landscaping problem, so it was win-win).

Something that is easy and important to check: Are your gutters working correctly? Are the downspouts discharging water far away from your house? Are your gutters clogged? Are your gutters poorly designed (i.e., too small for the roof area)? Is there a section of the roof that needs gutters but doesn't have them?

I recommend going outside in a rainstorm and checking how your gutters are performing.

Other questions: how humid is your basement if you turn off the dehumidifier? Do you see efflorescence (white powder on the walls) in your basement anywhere? Water almost always leave evidence...

[lindy rig]

Thanks for the information! I am on the verge of having a pro come look at it... but not even sure who to call. A buddy of mine is a contractor and has done some work for me but says not to worry about it, just monitor it.

Interesting point on the gutters. I do believe at least some of them are clogged. (I can see leaves sticking up in parts) The whole house does have gutters and the grading away from the house seems good. I was wondering if the clogged gutters could be a problem, but couldn't figure how that would equate to moisture / humidity in the basement.

[frazwood]

I have not looked for people in the Twin Cities (only in the Brainerd Lakes area), but there are companies that specialize in wet basements. You can also find a bunch of websites on the internet to suggest wet basement solutions. In theory, your friend the contractor should know someone too.

The clogged gutters can matter because all of the water from your roof is going to end up somewhere and if they aren't working properly, that water gets dumped right next to your foundation. This is the same problem if your downspouts discharge too close to your house.

Even so, your house is too new to have problems like this.

It's supposed to be wet the next few days. Take the opportunity to look around and see where rainwater ends up. You might be able to spot an obvious problem.

[panski master]

I have a house that is 10 years old like you and had the same issue. Here is what I determined and did.... The back of my house gets full sun from 1:00 til sunset due to no trees in my back yard. I beleive this was a big part of the issue. The houses now days are sealed so tight there is no room to breath causing a hot outside wall (from the sun)with a cool inside basement wall. Making the wall condensate. My basement was also unfinished with the basement door closed most of the time. With the door closed and no duct work (cold air exchange or heat vents) in the basement it limits the air exchange. I went and cut slits in the plastic vapor barrier to allow it to breath, ran a fan, and kept the door opened and it made a difference. I have a walk out with sandy soil and didn't have to worry about the rain and drain tile being the issue because mine has never ran. I finished the basement 5 years ago and the laundry room that I didn't finished I have not seen any condensation occur on the vapor barrier or insulation. I think this happens a lot in newer developements that are built in corn fields. Planting fast growing trees to shade the house is a must in my book. One, trees make a yard look spectacular and second its amazing how the shade it provides can make a difference. I especially noticed the difference in my lawn from having trees (less watering)and it will help with the cooling bill down the road. My trees are just starting to shade the back side of my house once the sun is at the end of its day but any little shade helps. I am no expert by any means and am not a carpenter but I hope this bit of info helps. Lets us all know what you find out and do.