Anyone insulate their TH floor?

Ours had insulated tanks on the forward two thirds of the floor and the rear was more exposed. You could feel the difference in freezing weather if you walked around in socks. We never addressed the issue while owning our TH.

Is the main floor insulated? Can you use the same type of insulation? Maybe the heating/cooling vents need to be looked at to make sure they are allowing free flowing heat/cold.

We don't have the separate garage so we don't notice the problem so much, but it is noticeable a little because the garage area doesn't have any heating vents. The vents stop in the kitchen/dining room area, so the living room/garage gets a little cool when it's cold outside, not so noticeable with the A/C since there are overhead ducting for the A/C.