I agree. Also, weatherstrip the windows and door down there- first.
The floor is cold due to the incoming outside air in the basement (making up the escaping attic air from the “stack effect”) permeating the joist bays and dropping the temperature of the floor joists, transmitting their temperature to you. Check your attic insulation R-value and air sealing of wiring/plumbing holes. Check the 1st floor above you (while in basement) for any similar holes that let air through. The decking is acting as an air/vapor barrier due to the exterior glue in the material. Any hole in an air barrier, no matter how small, will let through a lot of air due to the pressure difference between the basement/attic. The holes usually go through all floors and the wall top plates right to the attic; http://www.wag-aic.org/1999/WAG_99_baker.pdf
So you want to insulate the floor and treat the basement like a crawl-space; http://www.buildingscience.com/docum...ce-insulation/
Now you already have a basement….. some ways to insulate it; http://www.buildingscience.com/docum...g-your-basment
If dead-set on insulating the floor; http://www.buildingscience.com/docum...n-crawlspaces/
Either way, air-seal and insulate the rim joists- first; http://www.buildingscience.com/docum...m-at-rim-joist
AND, cover the dirt; http://dirt-crawl-spaces.com/crawlspace-dirt.html
Clothes taking longer to dry?
Clean the dryer screen in HOT water if using fabric softener sheets.
They leave a residue that impedes air-flow, costing you money.
Clean the ducting in the last six months? 17,000 dryer fires annually!