kimosabe wrote:

I have to insulate the floor in an older ranch house. It will be done
from underneath, which is a crawl space. (Ugh.)

Anyway, considering the usual array of pipes, electrical wires, and
cross-bracing between the joists that all tend to make the job more of
a hassle, what would be the most workable type of insulation to get?
I thought about rigid, but it would mean a lot of cutting and fitting.

If it turns out to be batting, that means the paper side would be
facing the ground. Is that OK?

Paper or foil side should face the warmer side, the house.

Do NOT use foam board, spray foam, or anything else flammable. Stick
with fiberglass or rock wool.