I live in Los Angeles, so we don't get very cold winters, though it will get down to freezing on occasion at night. We have a 1954 home with original hardwood floors. There is a crawlspace under the house, maybe 24" high, from dirt to the underside of my floor. The foundation walls have vents, open year round. In the Wintertime, the floor gets very cold. We dealt with it the last few years but now we have a baby crawling around and I'd like to solve the problem. I've been reading ****** about all sorts of options, but I suspect a lot of them vary depending on the climate you live in. I've read that insulating the underside of the floor will work, others say no. Some people say you can seal up the vents to the outside and install a crawlspace heater. I've read that sealing up the vents can cause mold issues. I've even read that hanging a few 100 watt bulbs in the crawlspace can make a noticeable difference.
The house is only 950 sq feet, so there's not a whole lot of crawlspace to heat. I've even considered trying to redirect some of the heat gathering at the ceiling, down into the crawlspace. Seems like it would do more good trickling up through my floor than collecting at the ceiling.