There are many options for you to choose from when it comes to insulating your home.

One of the most common ones is blanket insulation. But what exactly is blanket insulation and what types of insulation can be classified as blanket insulation?

Keep reading to learn if blanket insulation might be the best option for your house.

What Is a Blanket Insulation?

Researcher Dale Kleist accidentally discovered fiberglass in the early 1930s while attempting to create a vacuum between two glass blocks. Some of the glass was transformed into tiny glass fibers by the stream of high-pressure air.

Over the following ten years, this material was transformed into “blankets,” which were widely utilized to help make houses warmer and more energy-efficient.

Blanket insulation is one of the most popular types in modern home building and typically refers to pressurized insulation materials that can be formed into rolls or cut into batts of insulation. 

Insulation blankets are typically made of fiberglass, but can also be made from mineral wool or other natural fibers. The continuous rolls of insulation can be cut and trimmed to fit the space you need to fill, and it is available with or without facing.

Rolls can be up to 64 feet long with widths of 16 or 24 inches, making them ideal for wood framing, which employs the same measurements between studs. A 1-inch variant is offered for particular applications, including around sills and less-accessible locations inside brick walls. Thicknesses of blanket insulation include 3 inches, 6 inches, and 9 inches. 

Each of these has a different R-value depending on the material. The thermal resistance, or R-values, of typical fiberglass blankets, ranges from R-2.9 to R-3.8 per inch of thickness. R-values for high-performance fiberglass blankets (medium- and high-density) range from R-3.7 to R-4.3 per inch of thickness.

What Is The Difference Between Batt And Blanket Insulation?

There is a simple difference between batt insulation and blanket insulation. A single long roll of material is known as blanket insulation. If the material is cut into 4 or 8-foot lengths to be sold in a bundle, it is referred to as batt insulation. 

Where Is Blanked Insulation Used?

Because blanket insulation comes in a continuous sheet, it is often installed in areas of a home or building where there are few impediments. (impediments include things like pipes or electrical wiring.)

New construction utilizes blanket installation, placing it between joists, studs, and beams. As it improves energy efficiency inside the home, blanket insulation can often be found in attics. 

Materials Used For Blanket Insulation


When molten glass is spun to create fibers and then coated with a liquid binder, it creates fiberglass. The pieces are broken up, cooled, and put onto a conveyor belt. It piles into a tangle and is then sent through curing ovens. The finished product is cut into the needed lengths and widths. 

Fiberglass makes a good insulator because it slows heat, cold, and even sound from spreading through space. It traps the cold or heat in pockets of air which helps maintain a room’s desired temperature. While it definitely limits the amount of outside air breaching the house or building, it doesn’t eliminate it completely.

The R-value for fiberglass insulation generally falls between 3.1–3.4 per inch of thickness. Still, you can increase it by doubling or tripling the material. 

Mineral Wool

Mineral wool was one of the earliest insulation materials to be widely produced commercially. Also known as rockwool, slag wool, and stone wool, production began in Germany in 1871.

The process of creating mineral wool involves melting the raw material — stone or iron ore slag — at a very high temperature. It is then spun like cotton candy to create very thin fibers. The fibers are then coated with a binder to hold them together and shaped into insulation batts or board stock.

Due to its superior fire resistance, mineral wool has long been a popular choice for insulation in commercial structures. It resists fire without the use of any chemicals or flame retardant. Compared to fiberglass, mineral wool is a denser and heavier insulation material, which improves its ability to regulate sound and better obstruct airflow. 

Plastic Fibers

Plastic fiber insulation is made from polyethylene terephthalate or PET, which is mostly sourced from recycled plastic milk bottles. The plastic fibers are turned into insulation in a process similar to fiberglass insulation. The finished product is then treated with a fire retardant. While this keeps it from burning, it can still melt when exposed to fire. 

Plastic fiber insulation’s R-values vary depending on the density of the batts, ranging from R-3.8 to R-4.3. 

The insulation does not cause irritation like fiberglass, but it can be more challenging to work with. Special tools may be needed to cut and handle it. 

Natural Fibers

Natural materials, including cotton, wool, straw, or hemp, can also be used as insulation. 

Cotton: Recycled cotton, like from blue jean manufacturing, can be treated with pest repellent and flame retardant to create insulation. Cotton fiber insulation has an R-value of 3.4 per inch and can be installed without skin or respiratory protection. However, it is substantially more expensive than fiberglass.  

Wool: Sheep’s wool can be treated with pest repellent and flame retardant to create insulation, just like recycled cotton. The R-value is slightly higher than cotton at 3.5 per inch.

Straw: Recent years have seen a renewed interest in straw as insulation, something that was popular in the Great Plains region 150 years ago. The R-value of straw bale insulation is placed at 2.4 per inch due to the gaps between the bales. 

Hemp: Batts formed from the inner fiber layer of the hemp plant are used as insulation, and flax, polyester, or kenaf fibers can be woven into the insulation to serve as a binder. Compared to mineral and sheep wool, hemp insulation is less flexible and denser. It has an R-value of 3.5 per inch.

Pros And Cons of Blanket Insulation

Advantages of blanket insulation:

  1. Blanket installation is quite simple to install — especially during new construction.
  2. Blanket roll insulation is relatively easy to transport. 
  3. Paper- and foil-faced blanket insulation often have stapling flanges which make it even easier to install.
  4. Fiberglass blanket insulation is relatively inexpensive.
  5. Fiberglass blanket insulation is readily available meaning it will likely be in stock when you need it. 
  6. Rock wool blanket insulation is easy for DIY installation.
  7. Rock wool blanket insulation is highly flame resistant. 
  8. Cotton fiber blanket insulation does not cause skin irritation.

Disadvantages of blanket insulation:

  1. If your blanket insulation has a low R-value, doubling or tripling it to increase thermal efficiency will take up more space. You may end up needing a foot or more of insulation!
  2. Rolls of blanket insulation need to be hand cut to fit into smaller spaces.
  3. Blanket insulation can compress easily causing it to lose efficacy.
  4. Fiberglass blanket insulation can cause respiratory irritation.
  5. Protective clothing needs to be worn when installing fiberglass insulation as it can cause skin irritation.
  6. Rock wool and fiberglass blanket insulation can harbor moisture leading to mold or mildew problems.
  7. Cotton fiber blanket insulation can be more expensive than other options.

Blanket Insulation R-Value Chart

MaterialR-Value (per inch)
Mineral Wool3.0-3.3
Plastic 3.8-4.3

Alternatives To Blanket Insulation

Blanket insulation is not the only type of insulation by far. Here are a few alternatives that may match your need better.

Blown-In (Loose Fill) Insulation

Blown-in or loose-fill insulation is a loose material added to an attic floor or between stud and joist cavities. It is made from various materials, including fiberglass, styrofoam pellets, and cellulose material. 

Blown-in is a good choice when adding insulation to already finished areas, irregularly shaped areas, or around obstructions. It is less DIY-friendly because special equipment is needed to install. Blown-in is best done by a professional.


Almost every portion of your house, from the roof to the foundation, can be insulated with foam boards — rigid insulation panels. They work well for special applications like attic hatches. Still, They are also suitable for inside sheathing for basement walls and exterior wall sheathing. Board insulation offers strong thermal resistance, up to twice as much as most other insulating materials of the same thickness. The three materials most frequently used to create foam boards are polyurethane, polyisocyanurate, and polystyrene.

Spray Foam

Insulation materials made of liquid foam can be sprayed, injected, foamed in place, or poured. Spray foam insulation is often blown into finished walls, underneath floors, or used on attic surfaces. Since it can be used in even the smallest of places, it is a great way to create an efficient air barrier. It is especially effective around gaps in door or window frames or around plumbing penetrations.

Can Blankets Be Used As Insulation?

Some people find the term “blanket insulation” confusing and assume it refers to using actual blankets as insulation. While it is technically possible to use a blanket as an insulator, it is not a best practice. Blankets can absorb and retain moisture which would lead to mold and mildew problems. 

How Thick Is Blanket Insulation?

Blanket insulation is available in different thicknesses. You can find rolls that range from half an inch to several inches thick. The R-value will vary by the thickness of the blanket. However, thinner insulation can be doubled or even tripled to increase the R-value. 


Justin's been in construction for over 20 years in both new build and renovation. With experience in both commercial and residential construction, he specializes in healthier and more energy-efficient homes.

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