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

Cellulose is one of the three most popular insulation materials used in the ceiling and walls of modern homes, in addition to fiberglass and mineral wool. 

Therefore, if you’re planning to insulate a new home or upgrade the insulation of your old home, cellulose insulation is definitely one of the options to consider. However, before you decide, you should learn a bit about the pros and cons of cellulose insulation. 

Made primarily from recycled newsprint and denim, cellulose is eco-friendly and biodegradable. It is also fire-resistant, mold-resistant, inexpensive, and has a high R-value.

The pros and cons of cellulose insulation are closely tied to the material and how it is manufactured and installed. Plus, more than one type of cellulose insulation is available on the market.

As a result, the pros and cons will depend on which type of cellulose you have chosen and how (and where) it has been applied.

In other words, you cannot fully understand this topic without knowing a bit about what cellulose is, where it comes from, and how it works as an insulation material. 

So, let’s dive straight in and learn some more about cellulose insulation!

What is Cellulose Insulation?

Cellulose is one of the oldest insulation materials still used to this day. While it has been around for over a century, cellulose insulation only became popular in the 1950s, when fire-retardant chemicals like ammonium sulfate and boric acid were added to the material. 

Typically, cellulose insulates unfinished attic floors and existing enclosed walls. Cellulose is a popular insulation material for existing buildings because you do not need to remove an existing wall to install it. 

The loose-fill version of cellulose can be blown into wall or attic cavities with the help of special blowing machines. The tiny particles of plant fiber form an effective insulating material, which conforms to most structures and spaces without disturbing or dislocating the finish. 

A type of plant fiber, cellulose insulation can make your home more soundproof and draft-proof than before. It has a high R-value, meaning it can effectively resist heat flow to keep your home warm during the winter and cool during the summer.

You can learn more about the relative R-values of cellulose and Rockwool here.

The high R-value is because cellulose is mainly made from recycled paper, which comes from wood fiber. The cellular structure of wood is, by nature, quite resistant to the conductive flow of heat.  

A closeup of cellulose insulation fibers
As one of the main types of insulation, cellulose insulation comes with standard soundproof and draft-proof capabilities.

More than 70 percent of modern cellulose insulation is made from recycled newsprint, cardboard, and other paper types. To be precise, it is made from hammer-milling old and discarded newspapers.

This process uses little hammers to repeatedly beat the paper or cardboard until it is crushed and shredded into smaller pieces. 

The Cellulose Insulation Manufacturers Association posits that installing cellulose insulation in a 1,500-square-foot (139.35-square-meter) house will help recycle as much newspaper as a single person can consume in over 40 years. 

More than three million tons of discarded newsprint would be removed from the country’s waste stream every year through recycling if all new homes were to be insulated with cellulose. 

Cellulose insulation is heavily treated with non-toxic chemicals, including borax, ammonium sulfate, and boric acid, constituting over 15 percent of the finished product by volume. They help protect cellulose insulation from insects, mold, and fire.

That said, you might be wondering how cellulose attains the insulating properties. Well, this product is made from chemically-treated paper fibers. The chemical treatment of these paper fibers is necessary to:

  • Deter pests
  • Ensure the fibers stick together
  • Increase heat resistance
  • Prevent settling and compression 

Types of Cellulose Insulation

There are three primary types of cellulose insulation. Your insulation needs will depend on the structure of your home and the particular area that you want to insulate.

a yellow bag filled with grey broken up pieces of cellulose insulation
Cellulose insulation mainly comes in three widely-recognized forms.

Loose-Fill Cellulose

This type of cellulose insulation is the easiest to install and can be blown into attic cavities and floors. You can do this with the help of a blowing machine rented from your local home improvement store.

However, it would help if you had a reasonably accessible attic to install this insulating material.

Loose-fill cellulose insulation costs about $0.8 to $1.30 per square foot of coverage. It has an R-value of about 3.5 per inch of thickness. 

Dense-Packed Cellulose

This type is typically used to insulate the walls and floors of your living space, both in existing buildings and newly constructed ones. It will cost a minimum of $2 per square foot of insulated space.

Dense-packed cellulose behaves like a liquid, which allows it to flow into obscure cavities and bypasses, solidifying them. As a result, it can be used to solve air movement problems in parts of the house that are difficult to access or repair. 

Wet-Spray Cellulose

Wet-spray cellulose is almost always installed in newly-constructed buildings right before the drywall is put up. As the name suggests, this type of cellulose insulation has water (and some adhesive) added to it during application.

The water and adhesive enable the cellulose to adhere to the surfaces within the open wall cavities, making it an excellent way to obtain tightly sealed installations.

Generally, wet-spray cellulose costs about $1.25 to $1.75 per square foot.

Subcategories of Cellulose Insulation

Some other subcategories of cellulose insulation, such as low-dust and stabilized cellulose, are also available for purchase. However, most of these variants fall broadly within the three categories as mentioned earlier.

Stabilized cellulose is a type of wet cellulose that minimizes settling and helps reduce the amount of material needed to insulate a given area. Using less insulating material has two advantages—it reduces the overall cost of insulation and decreases the weight of the cellulose on the drywall.

Which, in turn, keeps the material from sagging and settling. Stabilized cellulose is widely used to insulate sloped roofs. 

Low-dust cellulose is a type of dry cellulose that contains a small amount of oil. The oil acts as a dust dampener, preventing the release of too much dust and debris when the dry cellulose is installed. The release of excessive dust during installation is one of the only drawbacks of cellulose insulation. 

Installers typically wear simple dust masks to prevent allergies and respiratory issues during the application process. However, low-dust cellulose uses a dust dampener to solve this problem. 

It is the ideal insulating material for homes inhabited by young children or the elderly. Low-dust cellulose might also be a good option if you are prone to allergies, are sensitive to paper dust, or have respiratory issues like asthma. 

A man in full PPE protective gear standing on an attic floor installing loose-fill grey cellulose insulation in between the wood trusses.
It’s recommended to take several safety precautions, such as wearing PPEs when installing cellulose insulation.

The Process of Installing Cellulose Insulation

Here is the basic procedure to install cellulose insulation correctly:

  1. Safety precautions: Make sure you have the necessary safety gear, including goggles, gloves, a mask or respirator, and appropriate clothing.
  2. Prepare the Area: Clear the space you’ll be insulating of any obstacles, such as stored items in attics or crawl spaces. Make sure the area is dry and free from any leaks or moisture issues. Seal any gaps, cracks, or openings that may allow drafts with caulk.
  3. Install Baffles (if needed): In an attic, you may need to install baffles to prevent the insulation from blocking the soffit vents. Place baffles in between the rafters to maintain proper ventilation.
  4. Measure and Calculate: Measure the insulation area to determine how much cellulose insulation you need. The product’s packaging or manufacturer’s instructions should provide information on the recommended R-value per square foot.
  5. Prepare the Insulation Machine: If you’re renting a machine, follow the manufacturer’s instructions for setup. Typically, you’ll need to load the insulation material into the machine and connect it to an electrical outlet.
  6. Start Blowing Insulation: Begin at the far end of the area you want to insulate and work your way backward. Keep a consistent layer of insulation as you go, ensuring that the insulation is evenly distributed.
  7. Maintain Proper Depth: For most attics, the cellulose insulation should be blown to R-38 (10-14 inches). Of course, you should consider your region’s climate for the ideal level.
  8. Safety During Installation: Be cautious about electrical wiring, exhaust fans, and other potential hazards. Ensure that insulation does not come into contact with non-IC (non-insulation contact) can lights, which can create a fire hazard.
  9. Inspect Your Work: After you’ve finished blowing the insulation, take a moment to inspect the area to ensure it’s evenly distributed and at the desired depth. Areas of concern include the pipes and HVAC systems.
  10. Clean Up: Clean the blower machine and dispose of any excess insulation properly. Seal the insulation machine’s hopper and disconnect it from the power source.
  11. Dispose of Waste: Dispose of any excess cellulose insulation and clean up the workspace.

Pros and Cons of Cellulose Insulation

Cellulose insulation has been popular with homeowners for decades, primarily because it offers numerous benefits. However, it also has certain significant drawbacks.

In this section, we will discuss at length the relative merits and drawbacks of cellulose insulation. 

Here’s a brief overview:

Pros of Cellulose InsulationCons of Cellulose Insulation
It is eco-friendly and sustainable. It generates a lot of dust during installation.
It is heat-resistant and has a high R-value.Cellulose insulation is prone to sagging and settling.
It is heavily treated with fire-retardant chemicals.Boron, a chemical needed for treating cellulose insulation, is currently in short supply.
It is resistant to pests, mold, and mildew. This material absorbs moisture easily. 
It is very affordable.All types of cellulose insulation require a vapor barrier.

Now, it’s time to dive deeper into the ideas and concepts outlined in the table above. 

Advantages of Cellulose Insulation

It’s Eco-Friendly

More than 70 percent of cellulose insulation is recycled paper. Hence, vast amounts of discarded newspaper and cardboard are put to good use when cellulose insulation is manufactured. 

Moreover, recycling paper usually involves a bleaching process through which the ink is removed. However, no bleaching is involved in recycling paper into cellulose since it will be shredded and pulverized during the manufacturing process.

Hence, few chemicals (and very little energy) are needed to turn waste paper into cellulose. 

No greenhouse gasses are used as propellants during the manufacturing process of cellulose insulation. Additionally, it contains more recycled material than any other type of insulation currently available. 

Heat-Resistance

Cellulose has an R-value of 3.2 to 3.5 per inch of thickness, which is higher than fiberglass and some other common insulating materials. The high rating is because it is made from paper, which contains wood fiber.

Wood has a cellular structure helps prevent air leakage and is naturally resistant to heat flow, making cellulose one of the most heat-resistant insulating materials available.

This resistance to the conductive flow of heat will help keep your cellulose-insulated home warm during winter and cool during the summer, thus minimizing your energy bills throughout the year.

You can click here for more ways to reduce your energy bills.

Fire Retardant

Cellulose insulation is treated with various non-toxic borate compounds like boric acid and borax. These chemicals constitute over 20 percent of the insulating material by volume. 

Known to be effective flame retardants, these chemicals were added to cellulose insulation in the 1950s to minimize the fire hazard in residential spaces.

As cellulose is made from recycled paper, it can be flammable without this chemical treatment. However, the addition of boric acid and borax has made cellulose insulation incredibly fire-resistant.

In wet cellulose, the presence of water makes the material doubly resistant to fire. 

Mold & Mildew

Chemicals like ammonium sulfate and boric acid have made cellulose insulation unpalatable for pests and inhospitable to the growth of mold, mildew, etc. 

This resistance to mold ensures that cellulose is healthy and hypoallergenic and makes it the perfect insulation material for those allergic to mold spores.

Even for those who aren’t allergic to mold or mildew, excessive exposure can also cause skin irritation and respiratory issues of various types. 

If appropriately installed, cellulose will enhance your comfort, improve your indoor air quality, and keep your home safe from fire hazards.

Affordability 

Cellulose is made from relatively cheap materials, such as discarded newsprint, cardboard, etc. The manufacturing process of cellulose, known as hammer-milling, is also quite basic and affordable.

It also makes it one of the cheapest insulation options on the market. It usually costs between $0.8 and $1.20 per square foot of insulation.

Cellulose insulation is also relatively easy to install. For instance, loose-fill cellulose can be blown into the attic (or a wall cavity) with the help of a rented blower machine.

This easy installation further reduces costs, as it can be installed over a DIY weekend with nothing more expensive than a dust mask and some rented equipment. 

Drawbacks of Cellulose Insulation

Dust Generation

Installing cellulose insulation can involve quite a bit of dust, debris, and general mess. Especially loose-fill cellulose, which, as the name suggests, consists primarily of loose pieces of fiber. 

The installer must wear a certified breathing mask to be safe from all that dust, and a lengthy cleanup process is required after the installation.

If you have a furnace duct system at home, you can expect some of that cellulose dust to be recirculated throughout your living space. 

Sagging and Settling

Cellulose insulation is prone to sagging and settling—a problem further exacerbated by the fact that it is several times heavier than comparable insulating materials, like fiberglass. 

The greater weight of cellulose naturally means that it is affected by gravity more than other materials, reducing the R-value of the insulation as the material sags and settles over the years.

Sagging can leave wide gaps in the wall cavities and minimize the insulating capability of cellulose. 

Modern cellulose is known to settle by as much as 20 percent, leading to uncomfortable living conditions and increased energy bills. However, wet-spray cellulose is typically more resistant to settling than the dry-blown variety. 

Moisture Issues

Cellulose insulation is known to absorb moisture easily, which can be a severe problem if you have a burst pipe or a bad leak in the plumbing. While other forms of insulation hold the excess moisture on the surface, cellulose absorbs it entirely. 

In fact, cellulose can absorb as much as 130 percent moisture by weight. Furthermore, the material dries slowly once the water is absorbed, leading to settling, deterioration, and mold growth.

Too much water absorption can even destroy the chemical fire treatment for which cellulose is so well known. 

Common Mistakes When Installing Cellulose Insulation

While most people consider installing cellulose insulation an easy job, it’s worth noting that when not done properly, it exposes your home to many issues. 

Mistakes done during the installation of cellulose insulation expose your house to structural problems, moisture, fire, and humidity risks. These are the things you want to avoid by ensuring your insulation is installed correctly.

Here are the mistakes you want to avoid when applying cellulose insulation:

  • Missing air leaks around the wires and pipes: Air leaks around these areas create drafts that bring outdoor unconditioned air into the house. When this happens, your HVAC system works more to maintain the indoor temperature. Consequently, you’ll use more electricity than expected. The best way around this mistake is to inspect your recessed light fixtures, plumbing pipes, and HVAC vents and ensure they are fully sealed.
  • Insufficient seal around the blower hose: Failure to seal the blower hose sufficiently has a similar effect to air leaks. You want to ensure that the area where the blower hose enters the wall is sealed with the insulation sufficiently to realize the full insulation benefits.
  • Insufficient insulation: Another mistake is applying insufficient insulation that doesn’t fill the area as required. You can prevent this mistake by blowing the cellulose insulation far enough into the eaves and corners of the attic. This will help you achieve consistent insulation. 

Where You Can Easily Buy Loose Fill Cellulose Insulation

The go-to for the easiest way to order would be the home improvement store nearest you.

a 25lb bag of Greenfiber cellulose Insulation that says All New Greenfiber across the top
The Greenfiber Blown-In Insulation is our recommended option for both convenience and affordability!

Concluding Note

Your location, local climate, budget, and the type of house you own are some factors that will determine whether or not cellulose insulation is beneficial for you. 

To learn more about cellulose insulation and discover whether or not it is suitable for your home, seek professional advice from architects and insulation technicians. 

You can also read our articles on What Is The R-Value Of Cellulose Insulation and Does Cellulose Insulation Create Dust for more information on cellulose insulation.

2 Comments

    1. Hi John! Thanks for the comment. Yes my understanding that in most cases cellulose can naturally settle 10-20, decreasing the relative R-Value with it unfortunately.

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