My house has a crawl space, and I can feel the cold coming up.

Short of adding insulation - get as large an area rug as you can. Make sure the gap between the floor and walls is filled in. You may have to caulk around it. Then put up trim. They also make insulation for behind switch plates. I added those for a room I have that just has a craw space.

This article might give you some good ideas! https://www.houselogic.com/organize-maintain/diy-repair/insulating-crawl-space/

If your crawlspace is accessible, Create a vapor barrier on the floor of the crawlspace, then insulate between the floor joists. This is a common problem and is best solved by doing the "big" job of proper insulation. Good luck.

You could add more insulation in the crawl space, or try Tyvek under carpeting, this will keep your floor warm.

Barbra is right on the money! A moister barier is extremely important if you don’t have one in good condition now? Otherwise you can have mold growing that can be very dangerous and unhealthy to breathe mold spores! That should be addressed first and then add insulation under the flooring. As a band aide you may be able to get some cans of spray insulation and have some shine a bright light on your floor while some is under the house looking up for cracks and spray some insulation in those areas to help air flow inside the house. But remember this is really only a band aide and your flooring will still be cold till you insulate it well!