The previous owner build an addition to the house and build basement under old portion of the house only, so on the bottom of the old portion he left empty space. So it's like empty space between floor and the fundament. There is no supporting beams and the floor is allways called. What can be done to fix that issue?

build basement under old portion of the house only, he left empty space so it's like empty space between floor and the fundament.no supporting beams and the floor is allways called
Insulate the fundament and the called space will be warmer
Post back if you need more details on how to do that and
Thank you!