Is Cellulose Insulation Better Than Fiberglass Insulation?

Insulation keeps your home’s interior temperature in check, ensuring that heat stays in for longer in the winter but escapes faster in the summer. Commonly, homeowners have to choose between fiberglass and cellulose insulation. Which is better?

Although cellulose insulation is pricier than fiberglass, it provides superior insulation to the latter. Cellulose is more environmentally friendly than fiberglass. But fiberglass lasts way longer than cellulose insulation and doesn’t need professional insulation like cellulose.

Inevitably, there is a lot more to know before choosing between cellulose and fiberglass insulation. What is each made of? What are their respective benefits? How thick should each be for maximum insulation efficiency?

Continue reading as we extensively compare both to assist you in making the best insulation selection possible.

What is the Composition of Cellulose Insulation (vs. Fiberglass)?

Cellulose insulation is 80% made from recycled materials, mostly paper. These recycled materials are treated with a chemical solution called boric acid.

This increases the cellulose insulation’s fire resistivity and makes them impenetrable to vermin and mold.

On the other hand, fiberglass insulation is 20% made of recycled materials, while the greater composition is of small spun fiberglass.

Here, the insulation is formed from plastic and further consolidated with tiny glass shards.

The process entails molten glass being worked into fibers and then getting plated with a liquid binder.

Raw materials like silica sand, soda ash, and limestone also go into the production of fiberglass insulation.

Some manufacturers further enhance their fiberglass material with calcinated alumina, feldspar, magnesite, borax, and kaolin clay.

Moving forward, these fibers are disintegrated into tinier shards which cool in a non-uniform manner after being collected in a mobile conveyor belt.

This belt transports the disorderly pile of fiberglass through ovens where it is cured. At this stage, the fiberglass is ready (unless loose-fill) and can be packaged according to the manufacturer’s width and length specifications.

What Does the Cellulose Insulation Cost (vs. Fiberglass)?

The cost of cellulose insulation is high. First, to purchase it, you have to pay anywhere between $0.80 to $1.75 or even more per square foot, compared to half a dollar for a square foot of fiberglass.

Also, unlike the fiberglass installation that you can execute on your own, cellulose insulation installation is not just a DIY event as it needs the expertise of a professional.

While you can install fiberglass on your own, you definitely need a professional installer to install cellulose installation. This is given the substantial specialized experience the latter needs.

The cost of installing cellulose installation varies with the type. If going with wet-spray cellulose, you can expect to pay (per square foot) between $0.60 to $1.80.

Dense-pack cellulose is more expensive and can cost between $1.95 to $2.35 per square foot. Note that these installation costs are not definitive as you may end up paying more in climes where you need higher R-values.

Benefits of Cellulose Insulation (vs Fiberglass)

Fiberglass and cellulose have their respective benefits. Let us look at each of these and how they contrast.

Environmental Friendliness

First, cellulose insulation helps the environment. This is because, since its composition is majorly renewable wastes such as paper and newsprints, this reduces paper waste, thereby keeping the environment greener. Besides, making it required less energy, thereby minimizing carbon emissions.

Fiberglass insulation is the direct opposite of this. It’s non-renewable as a result of its main glass composition. In addition, more energy is required in its production.

Insulation Efficiency

Furthermore, cellulose insulation has a higher R-value than fiberglass insulation. Also, it is said to be three times denser than fiberglass.

This means that it has a higher probability of serving its insulation purpose than its fiberglass counterpart. This includes thermal and sound insulation.

Thanks to the chemical treatment, cellulose insulation has high fire-retardant properties. In addition, it keeps out insects and does not allow dew to penetrate.

In addition, cellulose insulation is termed “green” and safe for the environment. This is because it is biodegradable, and its production requires far less energy consumption than that of fiberglass.

Unlike fiberglass insulation which is mostly installed in rolled-out batts, cellulose insulation is blown-in. As a result, it fills up every nook and cranny of the installation surface but does not distort its shape.

On the other hand, installing fiberglass insulation can slightly distort the shape of the installation surface.


On health considerations, cellulose insulation is safer than fiberglass.  Also, cellulose is biodegradable and therefore poses no risk to human health.

When it loses its potency as a truly of age, it simply bio-degrades. In 1994, fiberglass gained a bit of notoriety for its carcinogenic properties.

This means fiberglass could cause cancer upon sustained exposure. This can happen when you accidentally inhale the tiny glass fibers that are airborne during installation.

For cellulose, the health risks are negligible as it is majorly composed of paper.

Nonetheless, the health risk of fiberglass insulation can be eliminated if you kit yourself with the right protective masks during insulation.

For the homeowner, fiberglass poses zero risk if properly installed.

Fire Resistance

All this time, we have discussed where cellulose’s benefits beat fiberglass’. Next, let us switch the narrative and tell you where fiberglass’ benefits beat cellulose.

Fiberglass is way more resistant to fire than cellulose. Also, fiberglass boasts superior resistance to mold and moisture than cellulose.


Also, while both fiberglass and cellulose may sag over time, cellulose is more prone to settling.

With such settling comes a significant deterioration in its R-value. We will elaborate on this later in the guide.

How Thick Should Cellulose Insulation be?

An insulation’s thickness critically influences its efficiency (herein typified by its R-value).

Consequently, the thickness required for optimal efficiency varies across fiberglass and cellulose insulation.

To obtain an R-30 insulation rating, you would need fiberglass material 12 inches thick.

However, to obtain such an R-30 insulation rating, you would only need 8.1 inches of cellulose material.

This said, most states have their own recommendations for how thick your insulation should be.

It is ideal to find out what your state recommends and act accordingly. You can also go with the recommendations of a cellulose insulation expert who would have investigated the building to know the right thickness for the insulation.

How Long Will Cellulose Insulation Last?

Despite the type of insulation, varying factors such as weather and quality of the material used can make it not last as expected.

Cellulose insulation can stay for a long time, but since it is composed of mainly biodegradable materials, it begins to degrade faster than its fiberglass counterpart.

Though it can stay for up to 30 years, this degrading can start as early as 15 years.

Thankfully, if you notice the degradation and want to top up the insulation, you do not have to remove the previous insulation.

Simply add more layers of the cellulose insulation onto the previous one, and you are good to go for another long time.

Fiberglass, on the other hand, can last over 80 years if properly installed and carefully maintained afterward.

We earlier mentioned the susceptibility of cellulose insulation to packing and settling.

This, unfortunately, causes such cellulose insulation to suffer pocket formation, especially in the areas experiencing settling.

Such pockets can facilitate the transfer of cold and hot air inside your home. Conversely, fiberglass tends to retain its structural integrity longer.

By keeping its shape and form longer, it better resists settling.

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