What exactly is fiberglass insulation? Fiberglass insulation consists of extremely fine glass fibers. It is an insulation is that is commonly found in many homes. Fiberglass insulation comes in two different varieties. You can find fiberglass insulation in blanket form which is batts and rolls, and loose fill. Typically manufacturers produce medium- and high-density fiberglass batt insulation products that have a slightly higher R-Value than standard batts. Fiberglass can be placed in unfinished walls, floors and ceilings. It is fitted between studs, joists, and beams.