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 itself 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 is used to insulate 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 draftproof than before. It has a high R-value, which essentially means that it can effectively resist heat flow to keep your home warm during winters and cool during the summer.

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

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 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, which constitute over 15 percent of the finished product by volume. They help protect cellulose insulation from insects, mold, and fire.

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.

Loose-Fill Cellulose

This type of cellulose insulation is the easiest to install and can be blown into attic cavities and floors 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. 

a yellow bag filled with grey broken up pieces of cellulose insulation

Dense-Packed Cellulose

This type is typically used to insulate the walls and floors of your living space, both in existing buildings and in 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 aforementioned three categories.

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. 

To prevent allergies and respiratory issues, installers typically wear simple dust masks 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. If you are prone to allergies, are sensitive to paper dust, or have any respiratory issues like asthma, low-dust cellulose might also be a good option. 

Pros and Cons of Cellulose Insulation

Cellulose insulation has been popular with homeowners for many 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 a bit 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 gases 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 that 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. 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 quite 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 and 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

The process of 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 is over.

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 very 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. 

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. 

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