DaveX

Our (unfinished) basement is warm and smelly. I have a few ideas about it but wanted some outside input. First off, it can get very damp in the summer (we're in MN). There has been some sort of concrete barrier applied to the original wall (house was built in 1914) about 4 feet high that had a lot of staining on it. Inspectors have always said it would be best to leave that alone. There has also been evidence of damp areas on the floor but usually after a rain and there are never and areas of standing water. A realize there is likely a runoff issue which can be worked on. We have a dehumidifier working down there which is on quite a bit during the mid-summer I have it set halfway and it does turn off from time to time. I've painted the walls and floor with moisture blocking paint and there is no evidence of it peeling up or staining although it's only been a couple of months.
Here's the thing though: The basement gets very warm and there is a sort of musty smell. The basement ceiling has insulation in about 3/4 of it. I'm wondering if the heat from the dehumidifier is heating up the basement and the insulation is keeping the heat down there. I believe someone was living down there before we moved in so maybe that's why it's insulated. Could the insulation be part of the problem here? Is there a reason for it in an unfinished basement? Could there be mildew or mold growing in it or between it and the ceiling?
Now, for the smell. Mildew aside, we discovered that a rat was living in the house this past spring. We had someone come out and he poisoned and we found it a couple of days later. It had been storing cat food under our dishwasher. There was an amazing amount of it under there and it didn't smell very good. I was able to clean it out though. We determined that it was likely we only had the one rat and there's been no further evidence of any others. Anyway, under our sink the wall is sort of blown out a bit where the plumbing goes through and, when it gets real warm and humid there's an odor that seems to be coming from through there that is similar to what I smell in the basement. I'm not sure how long the rat had been with us but I know the smell was there at least last summer as well. I'm wondering if what I'm smelling could be left over from the rat and could it be exacerbated by humidity?

inspectorD

It could be everything you just said, rats tend to stink for a while. Take the insulation down is my opinion. If you get a change, then that was the issue. I do not like insulation in a basement, it collects mold from the dampness in the air and collects on the dust from living there. Then you get a musty smell.

Just my opinion of course, been in thousands of moldy basements.

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CyFree

First - Seems like you have two types of moisture problems in your basement. You are getting moisture from condensation and moisture from water infiltrating the concrete walls.
The dehumidifier might get rid of some humidity in the air but can't do much about the water seeping in through the walls. That needs to be addressed otherwise the water will evaporate inside the basement and your dehumidifier will not be able to keep up with the load.

I'd suggest an interior perimeter drainage system installed along the internal basement wall, to intercept water seeping in through the walls and the junction between the wall and the floor, diverting it to a sump pump system.

Since you seem to have a big condensation problem, a vapor barrier might be recommended. Waterproofing paints and sealants are not the best idea because they will not handle hydrostatic pressure and will eventually peel off.

The idea is to install a vapor barrier that will allow the water from the wall behind it to be diverted to the perimeter drain and keep it from evaporating into your basement. There are many products in the market that will do just that. From thick 20mil plastic liners to wall systems.

The energy savings alone will pay for the repairs overtime.

Second - Musty smells usually indicate the presence of mold. Even if you can't see it, it must be lurking somewhere. And my bet is... the insulation. Because you have all that moisture in the air, your insulation is probably damp and, if there is anything organic in it (such as paper) mold is feeding on it... Or on wooden floor joists.

I'd also take a look around that little blown hole under the dishwasher, if it smells musty as the basement. A plumbing leak or even rain water might be soaking the wall or insulation behind it... and since those tend to be organic...water + organic matter = mold.

I am thinking mold because it is a foul smelling fungus.If it it were something else, like a dead rat, urine or feces, it would smell much worse. It would not be something you'd describe as musty.

contour

Humid, hot and musty smell means probably mold. For the health aspects alone you should solve this as fast as possible. Better to pay for repairs and enjoy the house than to pay the doctor and enjoy the hospital. There is a bit of information about water leaks in basements on the site that I am reading these days: Repair that Basement Water Leak. Might help, who knows. Cheers!