Cellulose and fiberglass are both good insulating materials, although the merits of the two are always hotly debated. You, as the consumer, are ultimately responsible for understanding the pros and cons of each to make an informed decision. The best choice for one homeowner is not necessarily the best choice for another.
Cellulose is made almost entirely of recycled newsprint. Left untreated, the material would be highly flammable – not ideal when you’re talking about insulation. But cellulose is coated with chemicals that make it safe and fire-retardant.
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When it comes to performance, cellulose and fiberglass actually have a lot of similarities. They have fairly similar insulating abilities, or R-values, and neither is ideal in high-moisture environments. But fiberglass is far more common due to outdated fire-risk fears about cellulose and because it has been around longer.
Types of Cellulose Insulation
There are three types of cellulose, differentiated by where and how they are applied.
- Loose-fill is the term used to describe cellulose when it is installed on the attic floor. Fluffy, lightweight pellets of cellulose are blown in using specialized equipment called a hopper and blower. The loose-fill method can be used for new construction or in existing structures.
- Dense-packed means the insulation is being added to wall cavities or other enclosed spaces, either in new or existing homes. The insulation is blown in to the walls through small access holes that are drilled.
- Damp-spray (also called wet-spray) is used to fill wall cavities in new construction. It allows for application without the need for a temporary retainer, and it creates a better seal than other application methods.
How Much Does Cellulose Insulation Cost?
Loose-fill cellulose typically costs about $0.50 to $1 per square foot installed. The cost is similar to that of fiberglass batts but, if anything, slightly less. Damp-spray cellulose costs about $0.60 to $1.80 per square foot of wall space. Dense-packed cellulose often costs $2 to $2.25 per square foot installed.
Keep in mind that these prices are only meant to be guidelines – costs vary widely from one region of the country to another. The cost also depends heavily on the R-value, which varies from one brand and product to the next.
- Less air leakage – Both cellulose and fiberglass need to be combined with an air barrier because they allow air to pass through. However, cellulose does slow the flow of air to some extent, while fiberglass does not.
- Ideal for tight spaces – Because cellulose is always blown in or sprayed in, it is ideal for hard-to-reach areas and adding insulation to existing spaces. Fiberglass batts don’t offer that flexibility. You can add batts in easy-to-access places such as the attic, but not in between walls.
- Better insulator (sometimes) – Cellulose and fiberglass batts typically have similar R-values of about 3.2 to 3.8 per inch. However, loose-fill cellulose has a much higher value than loose-fill fiberglass, which claims about 2.2 to 2.7 per inch. (We’ll talk more about the different types of fiberglass later.)
- Deters pests – Varmin and insects are less likely to invade cellulose because of the chemical coating.
- Difficult to install – Installing cellulose almost always requires the skills and expertise of a professional. It is a difficult do-it-yourself project. Even professionals tend to find it more challenging than fiberglass.
- Moisture issues – Cellulose may absorb more moisture than fiberglass, although this topic is a major point of contention among experts. Talk to friends, neighbors or local real estate agents about their experiences with one or the other.
- Not recyclable – Even though cellulose is made of recycled materials, it is not recyclable like fiberglass.
Fiberglass is the most popular type of insulation, partially because it has been around so long. Picture the fluffy pink stuff. (Although that represents just one brand; fiberglass insulation also comes in colors like white and yellow). Most people are more familiar with fiberglass than cellulose, despite their similarities.
Just as the name implies, fiberglass is made of glass fibers. The material has long been recognized as a good insulator that is reasonably priced. Modern fiberglass is also increasingly eco-friendly, made with 20 to 30 percent recycled glass.
Types of Fiberglass Insulation
Fiberglass comes in two forms: blankets (rolls or batts) and loose-fill. Blankets are best suited for new construction and easy-to-access spaces such as attics, and they must be cut to fit precisely into wall spaces and other cavities. They are far more common than loose-fill fiberglass, which is blown in.
Fiberglass batts are sold in varying densities, with varying R-values. Standard batts typically have an R-value ranging from 3.2 to 3.8 per inch, while medium- and high-density varieties have R-values of up to 4.3 per inch.
How Much Does Fiberglass Insulation Cost?
Standard fiberglass batts cost about $0.50 to $1 per square foot installed. The higher the density and R-value, the higher the price: Batts for the attic cost more than batts for walls, for example, because they need to be denser. Some batts with very high densities cost upwards of $1 per square foot.
Blown-in fiberglass also costs about $0.50 to $1 per square foot.
Fiberglass Insulation Pros
- Easier to install – Do-it-yourselfers are more likely to have success with fiberglass batts than cellulose. However, mistakes are easy to make even with fiberglass, and they can lead to significant energy loss.
- Familiar material – Because fiberglass is so popular and it has been around so long, contractors have more experience working with the material. You probably won’t find as many local contractors that are experts in cellulose installation.
- Recyclable – Fiberglass is completely recyclable, even though it is made with a small percentage of recycled materials. Cellulose, despite being made from recycled materials, is not recyclable.
Fiberglass Insulation Cons
- Air leakage – Fiberglass doesn’t do much at all to slow the flow of air, while cellulose has some success. Air leaks can eventually lead to problems with moisture and condensation.
- Not ideal for extreme cold – The R-value of fiberglass lowers considerably in extremely cold climates, making cellulose a better choice.
- Health risk – Concerns have long been raised about the negative health effects of fiberglass insulation. The glass can irritate the skin and lungs of those who install it if proper precautions are not taken. But fiberglass is safe once it is installed.