I need to rent a dehumidifier to get the moister out from underneath my house and put down a moister barrier of plastic. How long do you have to let it run to really get the job done right..

Also you can get sand installed and removing the old insulation, and installing new, Www.facebook.com/top2bottomnc

There are a lot of variables that would factor in here. Size of dehu versus area, overall condition, insulation, etc. Bottom line is to bring your moisture level ( humidity) below 50% minimum. Lower if possible and it may require installation of a permanent dehumidifier in the crawlspace area.