Cellulose Vs. Fiberglass: Choosing the Right Type Of Insulation


Selecting a trustworthy insulation is key when attempting to build a home with lasting comfort. The two popular insulation materials, cellulose and fiberglass, offer good thermal insulation and a wide variety of R-values. Both materials have different qualities that can affect the performance of home insulation.

The best place to start in deciding on an insulation material is to understand what it’s made from and how it performs.

What is Fiberglass?

Fiberglass insulation is made from tiny glass fibers bound together using a resin or binder to create a wool-like texture. Fiberglass is manufactured in the form of batts and blown-in insulation with little to no degradation. It has strong thermal retention as well as noise control. 

There are three fiberglass insulation methods to choose from:

Batts are manufactured into tightly packed and ready-to-install precut strips. The batts are pre-measured to fit the standard width between studs on a wall,  resulting in a quick installation process. Fiberglass batts have a lower installation cost yet still provide strong thermal performance. 

Rolls are not precut like the batts, but they are commonly used for insulating. Due to their long length, rolls require the extra step of cutting for fit. However, it is worth the extra effort for air-tight insulation.

Blown-in is ideal for oddly shaped and hard-to-access wall cavities. This loose-fill insulation will require a blowing machine for installation. CertainTeed offers the Volu-Matic® III High-Performance Insulation Blowing Machine for maximum coverage.

What are the Benefits?

  • Budget-Friendly: Fiberglass insulation is not only lower in installment cost but also possesses a high R-value. Having optimal thermal performance will help keep energy costs low.
  • Variety: Installation options provide easy and secure coverage in attics, walls, basements, ceilings, and other rooms in your home. 
  • Durability: Fiberglass is mold, mildew, and naturally non-combustible, ensuring the insulation will last without deterioration for the lifetime of your home. 
  • Sound Control: Enjoy high acoustical performance, muffling exterior sounds and minimizing the spilling of interior sounds from one room to another. 
  • Easy Installation: Fiberglass is lightweight and flexible, easy for handling, precise cutting, and placement. 

What are the Drawbacks?

  • Air Leaks: Fiberglass is known as an air-permeable insulation and should be paired with an air sealing product, like CertaSeal to help meet air tightness requirements in the building code.
  • Improper Installation: During installation if the fiberglass insulation is compressed, it will not achieve its tested Thermal value.

What is Cellulose?

Cellulose is composed of approximately 80% recycled newspaper and 20% fire-retardant chemical binders, which can be harmful to the skin. It is popularly as a loose-fill form (blown-in), but is also available in the form of batt insulation. Cellulose insulation will aid in preventing drafts and reduce noise from a home’s exterior surroundings. 

There are three popular installation methods for Cellulose:

Loose-Fill has a similar installation method to blown-in fiberglass, using a machine to fill cavities or hard-to-reach spots. 

Wet-Spray insulation is applied onto wall cavities using dry insulation mixed with water. The wet spray acts as an adhesive, sticking to any surface to stop air filtration, and covering pipes and wires without gaps.

Dense Packed is a heavy form of cellulose insulation that is typically installed in an exterior wall assembly. This requires you to drill a 2″ access hole into the wall and then inject the cellulose using a tube to pack the cavity tightly. Dense packing is on the pricier side of cellulose insulation.

What are the Benefits?

  • Practical Application: Cellulose has effective application methods that ensure complete coverage in a wall, cavity, or ceiling.
  • High Coverage: The option to either dense pack or loose-fill an area allows for complete insulation coverage upon application.
  • Fire Resistant: Cellulose is primarily made from recycled newspaper, which might seem like a potential fire threat. However, it is treated with fire-resistant chemicals. 

What are the Drawbacks?

  • Mold Growth: Cellulose is treated against mold but it is still vulnerable to moisture. If it were to get wet, it would transfer the moisture to any wood in a ceiling, wall, or attic space, causing mold to grow.
  • Expensive: The insulation can be challenging to work and has more intensive installation processes, resulting in higher installment fees. 
  • Dust: When installed or shifted, cellulose can kick up dust that can get into your air vents, creating issues with air quality in a home.

Key Takeaway

Every home needs insulation. It is necessary to achieve quality comfort and protect a home from the impact of extreme weather–think freezing pipes. Knowing insulation is a must, you should choose a reliable product. Fiberglass offers excellent acoustical performance, is resistant to mold and mildew, installs easily, and is financially sensible. 

If you have any questions, we’re always available to assist you. Don’t hesitate to reach out!

Leave A Reply