So I bought a house where the basement is finished but later found out during this past winter which was very very cold that there was no insulation in the basement. I circled back to the previous owner and he said he build the basement with 2x3, without any insulation. It's not inhabitable in the winter months, too cold. What is my best and least expensive option for insulating this basement?

If the studs are covered with drywall, it will be a difficult task without ripping out the drywall. Is there any access behind the wall?

You ca blow loose insulation into the webs between the studs,making holes above the ceiling(if you can access there) and blowing down the openings,the white insulation doesn't settle like the older mica chips did and keeps things quite warm.I did this for a 100+ year old home from the outside in the winter,the heating bill more than halved after I finished)

Any more thought or comments are most welcome,:)

KBC