Fiberglass insulation
 

Where i live hydroponics supplies are all mail order. I've been able to manufacture or come up with replacements for just about everything. One idea that has come to mind, is to use compacted fiberglass insulation instead of rockwool. They are virtually the same material. Anyone thought of this? Would it work?

They are the same material with fire resistant chemicals added that aren't good for plants. That is what I read somewhere but never tried it myself. I have found that the so called experts don't always know what they are talking about so I would try it on a small scale to see what results you get.
Ron