A closeup of cellulose insulation applied in a wall and flooring of an attic

Choosing the best insulation for your home can be challenging. That is why we are comparing two of the most popular types of insulation head-to-head in this article. 

Cellulose and fiberglass insulation are two of the most common and cost-effective types of insulation. Homeowners across the United States use both types of insulation to protect their homes from thermal penetration. Both are eco-friendly and great for soundproofing but have some challenges as well. 

In this article, we will break down both cellulose and fiberglass insulation and compare them to give you the most comprehensive understanding of each insulation type.

Fiberglass Insulation

Fiberglass insulation is one of the most common types of insulation. Fiberglass has widespread use in everything from boats to insulation and everything in between.

It is a sustainable material made of recycled glass and is inherently eco-friendly. Manufacturers spin very fine strands of glass into structured layers or loose pieces.

A picture of un-faced pink fiberglass batts in the wall, with a man installing it

There are two types of fiberglass insulation, batts, and loose-fill. Each has its ideal purpose; however, they are flexible in their uses. Here is a breakdown of the two types of fiberglass insulation.

Batts

Batts are a structured type of fiberglass insulation that comes in thick rolls. When unrolled, batts insulation looks like a blanket.

Homeowners and contractors typically use this type of insulation in walls. It fits very well into wall cavities and does not settle over time.

Stacked, unrolled batts of fiberglass insulation

One of the most significant benefits of batts is they can be installed as a DIY project.

In large areas, you can layer batts on top of each other to increase the R-value and overall efficiency of the insulation. Batt also comes in several thicknesses to help customize the insulation to the area you need. 

You can use batts in an attic, though they are not quite as efficient as loose-fill because they don’t reach every corner of the area. In addition, there is no seal with batts in an attic, and even small spaces or cracks without insulation can cause long-term inefficiencies.

Loose Fill 

Loose-fill is an unstructured type of fiberglass insulation. Typically, a contractor installs it as it can be tricky to install as a DIY project. However, Loose-fill is great for attics and hard-to-reach places. Contractors install the loose-fill insulation by blowing it into the desired area.

Because it is blown, loose-fill insulation will reach every corner, crack, nook, and cranny of the area you are insulating, pretty much guaranteeing a comprehensive insulation installation. In addition, most contractors will install a mesh layer over the insulation to ensure it is spread evenly and does not shift or blow.

You can choose to use loose-fill insulation in walls; however, it can settle over time which can cause issues with the insulation distribution and effectiveness.

R-Value of Fiberglass Insulation

The R-value of any insulation type indicates the insulation’s efficiency. The higher the R-value, the more effective the insulation will be. There are different R-values for batts, loose-fill in an attic, and loose-fill in a wall. 

Batt-style insulation has an R-value of 3.1 to 3.4 per inch of thickness. So, if you have a standard 3 ½” thickness, the R-value will be around 11. There are other standard depths as well, shown in the table below. 

R-values for Batts Fiberglass Insulation

Standard Depth Approximate R-value
3 ½” 11
6″19
8″25
12″38

Loose-fill fiberglass has a slightly different R-value. The average R-value is 2.2 to 2.7 per inch of thickness.

This means to reach a higher R-value, you need more thickness than batts. Loose-fill insulation is easier to make thicker because of its amorphous form.

Pros and Cons of Fiberglass Insulation

Fiberglass insulation has several benefits and challenges. You should prioritize and customize each to the needs for your specific project. 

Pros:

  • Cost-effective: Fiberglass insulation is one of the most affordable types of insulation on the market. It ranges in price from $0.40 to $0.50 per square foot of insulation. 
  • Durable: Fiberglass insulation has a lifespan of over 50 years. When it remains dry, it will efficiently insulate your home for decades. 
  • DIY: You can install batts-style fiberglass as a DIY project, saving money on installation costs associated with hiring a contractor. 
  • Soundproofing: Fiberglass insulation provides good soundproofing through ceilings and walls. It can help reduce external noise entering your home. 
  • Eco-Friendly: Recycled glass bottles are broken down and spun into insulation to make fiberglass insulation. Additionally, it is recyclable, and there are no chemicals that could hurt the environment even when it decomposes. 

Cons: 

  • Not a Vapor Barrier: Fiberglass insulation is not moisture-resistant and, as such, cannot act as a moisture barrier. You can hire a contractor to install a vapor barrier in addition to the insulation, but it is an added cost. 
  • Sags: When fiberglass insulation encounters moisture, it starts to sag, affecting the insulation’s long-term efficiency and reducing the R-value over time. Additionally, mold can grow, which could cause air quality problems in your home.
  • Dangerous to Breathe: As evident by the name, fiberglass insulation contains glass. If you breathe in even the tiniest particles, it can harm your health.
    Additionally, it can irritate your skin if you touch it. If you do not install the insulation properly, the fiberglass particles could be present in your home air supply.
  • Personal Protective Equipment (PPE) Required: If you install the insulation yourself, you must have proper PPE, including a dust mask and gloves.
    It is also best to wear long sleeves and pants to avoid skin contact with the insulation. Touching or breathing in fiberglass insulation can be dangerous and irritate your skin and lungs. 

Cellulose Insulation 

Cellulose is probably the most common insulation material for residential homes. Manufacturers make cellulose insulation by combining recycled newsprint, denim, and other materials.

Not only is cellulose insulation eco-friendly to make, but it is also biodegradable. Of course, most manufacturers will coat it in chemicals to make it resistant to fire and mold, but the eco-friendly nature remains. 

There are three main types of cellulose insulation, each with its benefits, uses, and challenges. 

Wet-Spray Cellulose

Wet-spray cellulose is most used in new construction, not renovations on existing buildings. Contractors install the insulation before putting up the drywall. When applied, contractors add water and adhesive to it right before installing it in the area. 

Because it starts wet then dries, it creates an excellent seal, preventing inefficiencies in the insulation, such as gaps or cracks. The average cost of wet-spray cellulose is between $1.25 and $1.75 per square foot.

Loose-Fill Cellulose 

Loose-fill cellulose is very similar to loose-fill fiberglass insulation except for the material itself. To install loose-fill cellulose insulation, a contractor uses a blower to spread the product. This type of insulation works on renovations and new builds. 

a yellow bag filled with grey broken up pieces of cellulose insulation
The ecologicaly clean cellulose insulation, fabricated from recycled newsprint

The installation process helps seal cracks or potential leaks in the area where you install it. The average cost for loose-fill cellulose insulation ranges from $0.80 to $1.30 per square foot. 

Dense-Packed Cellulose

The third and final primary type of cellulose insulation is dense-packed. You can choose to install it for renovation or new construction projects. Dense-packed cellulose starts as a liquid. It provides an excellent seal for any potential air leakage. 

A man installes densed packed cellulose insulation it the exterior walls of a home below a window
Courtesy of Nuwool

Once the dense-packed cellulose dries, it has a nearly complete seal in the installation area. Unfortunately, this cannot be done as a DIY project because it requires pneumatic installation by a professional. 

R-Value

Cellulose insulation has a consistent R-value across the different types. Dense-packed cellulose is the most efficient of the three types of cellulose insulation. Here is a chart breaking down the R-values per type of cellulose insulation. 

Type of Cellulose InsulationR-Value (per inch of thickness)
Wet-spray3.6 to 3.8
Loose-fill3.5
Dense-packed3.8 to 4.0

Pros and Cons of Cellulose Insulation

We discuss the benefits and challenges of cellulose insulation below. You will notice that cellulose is like fiberglass insulation in some ways, but there are still some differences in the details. 

Pros:

  • High Efficiency: Cellulose insulation has a high R-value across all its types, making it very efficient in insulating your home. Additionally, all cellulose insulation types create an excellent seal to prevent unwanted air leakage in your home.
  • Eco-Friendliness: Cellulose insulation is made from recycled paper, denim, and other materials. It is environmentally friendly to manufacture and dispose of.
    There are not a lot of chemicals used in making cellulose insulation that could produce pollutants at any point in the life cycle of the insulation.
  • Fire-Resistant: Manufacturers use a fire retardant chemical to make insulation fire-resistant. Cellulose insulation has the highest fire safety rating possible for insulation material. In addition, it has been known to delay a fire for up to 25 minutes, a potentially life-saving amount of time. 
  • Mold-Resistant: The chemicals used to make the insulation fire-resistant also help to control moisture and pests. Mold cannot grow at all on cellulose insulation, preventing allergens from entering your home. 
  • Soundproofing: Cellulose insulation provides an excellent sound barrier to external noises. 

Cons:

  • Not a Vapor Barrier: None of the types of cellulose insulation can act as a vapor barrier. However, while mold cannot grow on cellulose insulation, it does absorb moisture fairly easily. You will need to install a vapor barrier in addition to the insulation.
  • Not DIY-Friendly: To install cellulose insulation of any type, you must hire a contractor. Pneumatic tools and blowers are needed to install different types of cellulose insulation. 
  • Sags: Similar to fiberglass insulation, cellulose insulation can sag and settle over time, which can diminish the R-value. 
  • Shorter Lifespan: The lifespan for cellulose insulation is between 20-30 years. In addition to being on the higher end of insulation prices, this means it will be a more considerable investment both upfront and long-term. 

Direct Comparison

This section will take all the information above and directly compare fiberglass and cellulose insulation. Hopefully, this provides an easy reference for you in your decision-making process. 

CriteriaFiberglassCelluloseVerdict
R-Value2.2 to 3.4 per inch of thickness3.5 to 4 per inch of thicknessCellulose insulation is more effective than fiberglass insulation
Moisture ResistanceAbsorbs moisture easily and sagsAbsorbs moisture easily and sagsBoth react equally to moisture
Durability50+ years20-30 yearsFiberglass insulation has a longer lifespan than cellulose
InstallationDIY friendly Challenging – you must hire a professionalFiberglass is cheaper and easier to install
Cost$0.40 to $0.50 per square foot$0.80 to $1.75 per square footFiberglass is more budget-friendly
Health RisksMust use proper PPE and installation techniques to avoid lung and skin irritation Installation processes cause a lot of dust. Therefore, proper PPE must be worn and do the extensive cleanup. Both have challenges when it comes to health risks 
Vapor BarrierIt is not a vapor barrierIt is not a vapor barrierNeither can act as a vapor barrier—a contractor must install an additional vapor barrier with the insulation
SoundproofingGood soundproofingGood soundproofingBoth are effective at soundproofing your home

Conclusion

Both fiberglass and cellulose insulation can add a lot of value to your home. However, they each have distinct benefits, types, and challenges that you must consider when deciding how to proceed with your insulation project. 

Fiberglass insulation is cheaper, and you can install it as a DIY project. Still, it can be susceptible to mold and sagging and has a lower efficiency rating than many insulation types.

On the other hand, cellulose is mold and fire-resistant and has a higher R-value but is more expensive and has a shorter lifespan. However, both are effective at soundproofing and are eco-friendly, but neither can be used as a vapor barrier. 

Factor all of these details into your decision-making process to help you choose the most suitable insulation solution for your home.

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