Is it practical to install netting for crawlspace insulation to help keep loose insulation in place? If so how is it fastened to the floor joist and where can I find the netting?
I had to insulate a crawlspace with joists at 24" on center, no-one seemed to have insulation hangers that length locally, and there was some urgency about getting it done. I had some 1" roofing nails and a ball of mason twine. I started in one corner, drove a nail part-way into the first joist a foot or so from the end and tied the end of the string to it, then drove the nail the rest of the way. I then went to the next joist, drove a nail part-way, looped the string around it, pulled it tight, and drove the nail home. I proceeded like this across the space, then repeated the process a couple of feet further along the joists. I went back and forth like this until I got to the far end of the house. The building inspector approved it, and the insulation was all still in place five years later when I went under there again. I would have used insulation hangers if I had been able to find the length I needed at the time, though.
If insulation hangars don't work for you, I've seen poultry netting (aka chicken wire) stapled to the joists to hold insulation up. If you do this, be careful that it doesn't touch metal pipes, as you will get corrosion due to dissimilar metals.
This could make a very neat installation if you're inclined to be bothered by sagging in between hangars, but it could be pretty tedious cutting the netting and installing it carefully so that no wire points are exposed.