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?