Benefit: The material itself lends to its popularity as fiberglass is chemically stable, will not rot and is nonflammable. All of these characteristics give it appeal for inside the walls of your home.

 Drawback: It does melt with enough heat, so unlike cellulose insulation it offers no fire retardant properties to the home. Also, it is not water resistant and will readily absorb moisture; thus it is a poor choice in damp or wet locations.

 Benefit: Fiberglass insulation is manufactured in a number of useful forms including: Fiberglass rolls, batts, blankets, and loose fill.

 Drawback: rodents love fiberglass, and eagerly make their little nests in it when they can, thus, if your home is not sealed well, you might be attracting mice, rats, etc. with this choice of insulation.
Now that we have looked at a few of the benefits and drawbacks of fiberglass insulation in general, let's take a look at what the different forms of fiberglass insulation offer:

Fiberglass rolls are very useful for custom built homes as they are available in various widths and lengths for use between the framing members of walls, ceilings and on attic floors.

Fiberglass batts are not much different from rolls. They too come in different widths, and in fact they are really the same as rolls, except that they are bundled in precut lengths to make installation in standard 8' walls easier.

So, for a typical or standard building or house, fiberglass insulation in the batt form is both convenient and useful.
Both batts and rolls have an attached vapor barrier facing to protect them from moisture and thus make your insulation last longer and work better. This vapor barrier facing is supposed to be stapled onto framing studs to keep the insulation in place prior to the installation of the wallboard or plaster. Paper is the most common facing, but there is also an aluminum facing which adds additional heat reflective properties to the insulation, but also causes an increase in price.

Fiberglass blankets are another form, and are similar to batts in that they are sold in precut lengths. However, fiberglass blankets do not have a vapor barrier facing. So, why not? Well, the fiberglass blankets don't need this because they are designed to be installed over the top of existing insulation (which already should have the vapor barrier) in locations such as the attic floors. This is done to increase the R-value, not as the primary insulation layer. So, never try and use fiberglass blankets as your sole source of fiberglass insulation, but rather as a reinforcement of insulation.

Loose fill fiberglass is also used for attic floors. It can be poured or mechanically blown onto attic floors, making this the fiberglass product of choice for quick retrofitting of insulation into older buildings or into areas with limited access for the installation of batts.

Loose fill does not have any sort of vapor barrier because it can't. it is blown in, and is great for those hard to reach areas, but installation of a vapor barrier is essential with fiberglass insulation, so it should only be blown into areas that have a vapor barrier; this is why blowing loose-fill fiberglass insulation into existing walls is not advisable, fiberglass insulation soaks up water like a sponge, causing a pronounced drop in its insulating ability, and can even cause mold to form in your walls.

While the most popular form of insulation, one big downside to fiberglass insulation is that it is a scratchy, irritating product if it comes into contact with any or all body parts. Contact with skin should be avoided, so when installing fiberglass insulation use gloves, long sleeves, and any other protective clothing and eye protection you can. You will also want a quality dust mask or respirator whenever working with fiberglass.