There’s parts of the country where it doesn’t regularly get cold enough for insulation to really matter.
That said, my house in the Chicago suburbs is over 140 years old and was definitely never insulated underneath. By the feel of the walls in the winter any insulation that was in there has probably all collapsed as well.
Insulation in the floor is really much less important than walls/roof. Heat rises so if you wanna trap heat the ceiling is most important. And in the summer the basement is usually the coolest part of the house. Basically only matters if the floors being cold to the touch bothers you in the winter, and a very modest energy savings (likely never will recover the install cost).
There’s parts of the country where it doesn’t regularly get cold enough for insulation to really matter.
That said, my house in the Chicago suburbs is over 140 years old and was definitely never insulated underneath. By the feel of the walls in the winter any insulation that was in there has probably all collapsed as well.
But… Insulation also insulates in summer against heat?
Insulation in the floor is really much less important than walls/roof. Heat rises so if you wanna trap heat the ceiling is most important. And in the summer the basement is usually the coolest part of the house. Basically only matters if the floors being cold to the touch bothers you in the winter, and a very modest energy savings (likely never will recover the install cost).