don't replace it. fiberglass will compress a little over time and lose some of its insulative function but shouldn't have to be replaced because it is still working just not as efficiently as when new. Add more if your'e concerned about it. Nowadays 6 to 8" is minimal and 10 to 12" in extremely cold or hot climes. It'll pay for itself fairly quickly. It's a little like sex, a lot is way better than a little!!!
fiberglass
Yes, especially if it is made of fiberglass and the fibers get into your skin. That is why insulation should only be handled with heavy gloves and long sleeves.
Fiberglass is a very strong material that is good for insulation.
Fiberglass is not combustible; at high temperature fiberglass is melted.
copper
Fiberglass is a good insulator. It's often used in home insulation!
Fiberglass is a good insulator. It's often used in home insulation!
acetone
Plastic. fiberglass. ceramic. cork, eider down is not the insulation... the insulation is the dead air in the small cells plastic is combustible, glass is not fiberglass is a better choice for habitable areas
Foil and Fiberglass Duct Insulation is best.
Dogs can get sick from eating fiberglass insulation. If you find your dog eating fiberglass, take him to a vet immediately.
In the case of fiberglass insulation, it's silica, either from quartz or feldspars.