We have a basement that is 1/2 unprofessionally finished. When it is very cold out we get a smell that I say smells like wet carpet, my husband says smells like the septic system. It seems to only be on the finished side (which has a new 9x12 bounded carpet that is not wet). The septic system is in the unfinished side in the front of the house. The washer machine always has a slight septic smell when I open it, but never any water (we think there may be a block in the roof vent, but weather is stopping us from checking). I'm not convinced that the smell is from that though, seeing when I walk in that room the smell seems to go away. The funny thing is that the smell just came a day or 2 ago when the weather here got close to 0 degrees. I have noticed condensation on the basement windows. Do you think the smell is from the 9 x 12 rug, even though it isn't wet?? I'm curious to see if the smell goes away when the weather hits 30 degrees in the next few days. Any suggestions would be appreciated. Thanks.