Sorry for shouting,,lol,,,want to replace 40 year old fibrglass insulation in basement ceiling with new,joist are 16 inches apart and 2x8 sized,,,what size insulation should i use
=== maybe you use the basement a bunch or not so much SO, you do need to insulate that ceiling to make it energy efficient the higher the R-factor the better the savings and the warmer that it will be above the basement ceiling ..... buy the stapler tacke
You should use R-19 which is approx. 6 1/4 thick. The next size up is R-30 which is 9 1/2 thick.
You provided all the information that DOESN'T matter and none of the information that does. If the basement is heated, FORGET the insulation. The only thing it is doing is dampening sound, and there are better options for that. If the basement is unheated, the answer depends on local climate. You need more insulation in Alaska than in Hawaii.
Why are you insulating the ceiling of a basement,? Unless there is no heat in the basement it is not efficient to insulate the ceiling from a heating stand point. But it's your ceiling. Size 15x 93 batts R factor 19