A closeup of cellulose insulation applied in a wall

One of the oldest forms of home insulation, cellulose, is a material made primarily from recycled newsprint and denim. 

The high concentration of recycled materials in cellulose makes it one of the most eco-friendly forms of home insulation. Cellulose is also popular for its relative ease of installation, high R-value, and flame-retardant properties. 

R-value measures the resistance to heat flow offered by an insulating material. In other words, the higher the R-value, the better its insulating ability. 

What is the R-Value of Cellulose Insulation?

The R-value of cellulose is between 3.2 to 3.8 per inch of thickness. Such a range exists because the exact R-value per inch of cellulose can vary slightly, depending on the size, shape, and construction of the building being insulated, the production methods of the cellulose manufacturer, and the typical weather conditions in the area. 

As a point of comparison, you can check the R-value of other common insulating materials such as fiberglass, foam board, and rockwool.

Learn more about the R-values of foam board insulation here. 

Here’s a chart for a quick, visual comparison.

Type of Insulation R-Value
Fiberglass2.2 to 3.8 per inch, depending on loose-fill, blown-in, or fiberglass batt insulation.
Foam BoardApproximately R-5 per inch of thickness.

RockwoolBetween 3 to 3.3 for each inch of insulating material.

CelluloseBetween 3.2 to 4.0 per inch of thickness.

Air leakage, also known as convection, is one of the major factors responsible for heat loss in modern buildings. Conditioned air often leaks out through cracks and gaps in the building envelope, accounting for over 40 percent of the total energy loss in a given year. 

Cellulose is an excellent air-blocker, meaning that it can minimize heat loss through convection. Hence, it can provide great comfort and energy savings when insulating a home or office. 

Types of Cellulose Insulation

Cellulose insulation is incredibly versatile. Therefore, when deciding which type of cellulose insulation is best for your home, you will have three primary options to choose from. They are:

Loose-Fill Cellulose

This type of cellulose insulation is typically used in attics and installed with the help of a blowing machine. It is a granulated or fibrous insulation material made from cardboard, paper, and paper stock.

a yellow bag filled with grey broken up pieces of cellulose insulation
Loose-fill cellulose insulation is made from recycled newsprint.

Loose-fill insulation material is relatively easy to apply, as it can be blown into the attics and finished wall cavities that need to be insulated. 

Dense-Packed Cellulose

Typically used to insulate walls and ceilings, this type of cellulose insulation requires neither ventilation nor a vapor barrier. Instead, this method involves packing as much of the material as possible into a given space.

A piece of dense-packed cellulose insulation

The increased density of insulation material ensures that dense-packed cellulose offers a higher R-value than other types of cellulose. 

Wet-Spray Cellulose:

With this type of cellulose insulation, water and a binder compound are added to the insulating material. The liquid cellulose is then sprayed into the space that must be insulated.

The binder compound ensures the cellulose will stick into the area sprayed. As a result, wet-spray cellulose can be used to seal and insulate a space simultaneously. 

Here’s a chart to help illustrate the R-values of the different types of cellulose insulation.

Type of Cellulose Insulation R-Value
Loose-fill celluloseAround 3.5 per inch of thickness

Dense-packed celluloseBetween 3.8 and 4.0 

Wet-spray cellulose3.6 to 3.8 per inch

Benefits of Cellulose Insulation 

One of the oldest insulation materials still used in modern homes, cellulose has stood the test of time because it offers numerous benefits to homeowners.

Increased R-Value

Loose-fill cellulose insulation offers an R-value of around 3.5 per inch of thickness, while densely packed cellulose boasts an R-value between 3.8 and 4.0 per inch. 

This value is higher than other insulating materials within a comparable price range. For instance, loose-fill fiberglass typically has an R-value around 2.5, while loose-fill rockwool offers an R-value of 2.8 for every inch of thickness.

As mentioned earlier, a higher R-value means better insulation. In other words, cellulose insulation will help keep your home cozy and comfortable, regardless of the time of year. As a result, you’ll save a substantial amount of energy that would otherwise have been used for heating and cooling your home. 

Effective Sound Barrier

As an insulating material, cellulose offers excellent sound insulation, minimizing noise transmission to and from your living space.

Cellulose ensures that unwanted external noises – such as the sounds of traffic and loud pedestrians – will not disturb the peace of your interiors. 

Cellulose also minimizes sound transmission from one room of the house to another. Therefore, it is a great way to increase the privacy and tranquility of your living space. 

The density of cellulose ensures that it can absorb almost 80 percent of the sound that it comes into contact with, which is why most cellulose insulation products have a Noise Reduction Coefficient (NRC) rating of .80 or higher. 

Environmental Sustainability

Cellulose consists of more recycled materials (mostly paper, denim, etc.) than any other insulating material on the market. Cellulose insulation also does not use any greenhouse gases as a propellant.

Furthermore, cellulose insulation can help regulate the temperature of your home, reducing the energy required for heating and cooling and, hence, lowering your overall carbon footprint. 

It also hardly produces any pollutants during the manufacturing process. All of these factors make cellulose an incredibly eco-friendly insulating material. 

And while the fire-retardant chemicals used during the manufacturing process prevent old cellulose insulation from being recycled into new insulating products, the material is nonetheless fully biodegradable.

Flame Resistance

Cellulose insulation gained popularity during the 1950s when fire retardant chemicals were added to the insulating material. Boric acid, ammonium sulfate, and borax are just some of the flame retardants that cellulose insulation products are treated with. 

Most cellulose manufacturers use a combination of borate and ammonium sulfate for fire safety. This thorough borate treatment affords cellulose a Class I fire safety rating, the highest an insulating material can get. 

According to trials conducted by various rating agencies, cellulose insulation can provide up to 50 percent more fire resistance than comparable insulating materials, delaying the spread of a fire by as much as 25 minutes.

During a house fire, 25 minutes could be the difference between life and death for you and your loved ones. 

Mold and Pest Prevention

The flame-retardant chemicals that cellulose is treated with also help prevent pest infestations. As the chemicals are toxic to pests, they minimize the risk of infestation in homes where cellulose insulation has been installed.

Cellulose insulation also offers excellent mold and mildew resistance. The chemicals mentioned above, like borate and ammonium sulfate, ensure that mold cannot grow and spread on the material’s surface. 

Apart from keeping your home clean, dry, and sanitary, this can also help prevent allergies and other respiratory issues since mold and mildew are common allergens. Click here to learn more about the link between home insulation and health. 

Affordable and Easy Application

Made from recycled newspaper, cellulose is one of the most inexpensive insulation materials currently available. It can also be easily applied to the most remote and inaccessible nooks and crannies in your home. Simply blow the loose-fill cellulose into the stud cavities, and it will eventually settle into all the nooks and crannies.

You can rent a blowing machine from your local home improvement store before using it to blow cellulose insulation into your attic (or any other inaccessible space you want to insulate). For an experienced homeowner, this will be no more than a simple weekend DIY project.

Application Process of Cellulose Insulation

Even the highest quality insulation material will not do much good if it isn’t correctly installed. Proper application or installation of the cellulose will determine its effectiveness in insulating your home.

A man in full PPE protective gear standing on an attic floor installing loose-fill grey cellulose insulation in between the wood trusses.

Start With Some Air Sealing – The Low Hanging Fruit of Home Efficiency

When installing cellulose insulation in your home, the first thing you need to do is to seal all the gaps and holes in the building envelope. Air sealing can be done quickly with simple tools like a caulk gun and a spray bottle containing insulating foam. 

You can start by sealing all the leaks in your attic, particularly around the pipes, fan housings, electrical lights, wires, and junction boxes. Also, don’t forget to seal the areas where the wall plates intersect with the attic floor. 

Similarly, you must carefully seal all the leaks in the basement ceiling to block all the potential air infiltration points. If possible, fill all the gaps and holes in the wall framing, particularly around the electrical and plumbing penetrations. 

Begin The Cellulose Insulation Install

After all the leaks, holes, and gaps have been thoroughly sealed, you begin to install the insulation. You can use a rented blowing machine to blow dry cellulose fiber (loose-fill cellulose) into an enclosed wall or an open attic. 

You will need at least one other person to operate the equipment properly. While one person will feed dry cellulose fiber into a hopper, the other will be responsible for operating the hose. This hose is attached to the blower and will extend to where the insulating material needs to be deposited.  

Wet-spray cellulose, on the other hand, is sticky and damp. Water and adhesive are added to the bare cellulose fiber to get the material for wet-spray cellulose.

It can be sprayed directly into an open wall cavity in a newly constructed building, leading to a wall cavity that is airtight, solid, and totally filled. 

Wet-spray cellulose is applied with the help of a water hose that incorporates a high-pressure nozzle, similar to a pressure washer. A mist of water dampens the surface of the wall cavity as the cellulose insulation is applied.

Water makes the material sticky, increasing the bond between the insulating fiber and the framing materials of the building. 

Therefore, the water flow should be adjusted to ensure the fiber is damp enough to adhere permanently to the wall cavity but not so wet that it will later cause dampness and moisture problems in the house. 

Concluding Note

Cellulose insulation is inexpensive, eco-friendly, and can offer R-values of up to 4.0 per inch of thickness. But unless you have lots of experience with DIY home repair and up-gradation projects, you should leave the installation process up to the professionals. 

Proper installation is essential to the performance of any insulation system, including cellulose insulation. So, before you hire an installer, be sure to ask for a list of references and call them for more information about the quality of the service they received.

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