Which Insulation is Better, Fiberglass or Cellulose?

Find Out Which Insulation Is Most Beneficial For Your St. Louis Home!

Sometimes, when discussing loose-fill attic insulation, it seems like a fist fight is going to break out between fiberglass supporters and those who prefer cellulose. Who is right? At Dr. Energy Saver St. Louis we prefer cellulose for blown attic insulation, most of the time.

First, some background. Fiberglass insulation is made from glass spun into small fibers. Cellulose is made from plant materials such as newspaper or other recycled materials and treated with fire-retardant chemicals such as borate. Both serve the purpose of resisting the flow of heat. The resistance of these products are determined in the laboratory and is referred to as the R-value of that product.

Many people are familiar with fiberglass insulation batts that are installed inside wall cavities and with fiberglass insulation rolls that were once installed on attic floors between the joists. We are not concerned with this type of fiberglass insulation batts or rolls. For this discussion, we are concerned with loose-fill fiberglass and loose-fill cellulose insulation only. Loose-fill insulation is blown into attics.

Now for the fist fight. In one corner, we have the fiberglass manufacturers. In the other corner, those who make cellulose.

In support of their case, fiberglass devotees usually claim the following advantages for fiberglass insulation:

• Fiberglass settles much less than cellulose
• When fiberglass gets wet it absorbs much less moisture, dries faster, and regains its resistance to heat flow faster than cellulose
• Fiberglass won’t combust whereas time and exposure might rob cellulose of its fire-protective chemicals
• Manufacturing of fiberglass insulation includes use of recycled products

 Cellulose advocates usually claim their own set of advantages:

• Cellulose has a higher R-value per inch at 3.2 to 3.6 (settled) compared to fiberglass at 2.6 to 3.0
• Cellulose maintains its resistance to heat flow better than fiberglass at lower temperatures
• Cellulose resists the flow of heat by convection and other airflow better than fiberglass
• Cellulose is treated with Borate (fire retardant) so as not to combust
• Manufacturing of cellulose is friendlier to the environment than fiberglass due to greater use of recycled materials
• Cellulose does not irritate eyes, skin and respiratory system the way fiberglass does

All things considered, with a higher R-value per inch and better resistance to heat flow through air movements, we believe cellulose insulation safely does a better job of making your home energy efficient. After all, isn’t that why we use insulation in the first place?