I did put 3/4 foam board insulation on the floor and then put 3/4 wood flooring. I would have thought that that would be enough. But, NO!
It is in the low teens here at night. The floor is cold. The rugs I have put on the floor help.
Now I want to tell you of a cool (warm) idea that I thought of a couple years ago. I got this "heated pet pad". It is made to go into dog houses. It is a plastic pad that is almost an inch thick. It has an electric element that heats the pad when there is pressure applied on top of it, as when the dog is in the dog house. Otherwise it is not on, so it is not using electricity.
It plugs into a regular electrical outlet. Mine is the larger size. It is 100 watts. It is 3 feet by 2 feet. They make smaller ones as well.
SO, what does this have to do with warm feet? I put this pad under my desk,and now I can sit there with my feet on the pad and have comfy warm feet.