Cellulose Vs Fiberglass Insulation [Detailed Comparison]

One of the most necessary elements of home improvement to complement your entire home’s comfort is insulation. Scorching heat or not-so-good weather conditions can often directly hinder your house’s temperature levels. Or you may say, after attending a hard day at work, your home embraces your exhaustion!

Now, when it comes to choosing insulation, you have several options out there. Today, we’ll be comparing two of the most common ones, cellulose, and fiberglass. One way or the other, by the end of this article, you’ll be sticking by any one of them.

Fiberglass insulation is primarily derived from glass particles and remains to be one of the most commonly preferred kinds of insulation. Cellulose insulation, on the other hand, is made from recycled paper and holds extraordinary mold-resistant properties.

You can extract an understanding of the distinct features held by both insulation types from the table below: 

Cellulose InsulationFiberglass Insulation
Made of recycled paper.Made of fine glass fibers.
Pest and fire-resistant. Mold and mildew resistant.
Comes in loose-fill form.Comes in both batts and loose-fill.
Poses no threat to human skin.Health risk for human skin. 
Dense composition allows withstanding extreme temperatures.May not perform at best during extreme weather conditions.
Cellulose vs fiberglass insulation

Until now, you might have gotten an idea of the core differences between the two types of insulation. Now let us dive into our in-depth comparison:


R-Value can be the single most influential factor in determining the right type of insulation for your home. It is the most demanding property held by any insulation. R-value is the resistance of the insulation against the transfer of heat energy or a measurement of thermal resistance.

The greater the R-value quotient for any insulation, the higher the performance of the material trapping thermal energy. The R-value of cellulose is slightly higher than fiberglass. Cellulose’s R-value is 3.5 per inch whereas fiberglass has an R-value of 3.1 per inch. Once again, the difference is barely significant so we’ll consider this one our first draw.


The durability of any insulation depends on how far insulation lasts without losing its functional value. Cellulose goes a long way in terms of its unmatchable insulating benefits but it can’t stay for a noticeable duration. This is because cellulose starts sagging with time. Fiberglass is still the first choice for its lifelong warranty. However, the longevity and durability of both materials are highly dependent on proper installation and aftercare. The best insulation is expected to last up to at least 5 years. 


Ease of installation can greatly affect an insulation’s value in the market. How long it takes to put up the entire insulation makes a remarkable difference. An insulation blower is used to install cellulose insulation. The blown fibers stick onto the space blown from the hose. On the other hand, fiberglass insulation comes packed in the forms of both batts and blown-in. Batts can be installed in a DIY project but for loose-fill, professional assistance is required to handle the installation. 


Cost-to-quality ratio of insulation is the most searched factor in choosing an insulation material. Both cellulose and fiberglass are almost equally costly and are relatively cheaper than most fancier options. However, investing in the top-quality insulation material is more sustainable than not going for one at all. The reason why these are quality investments is their potential to cut down the increasing energy bills. To sum it up, there is a draw between both insulation types when it comes to cost and affordability. 


An insulation material is not only comfortable for your home but also must serve the environment equally. Both cellulose and fiberglass insulation materials don’t induce or promote any environmental hazards. The insulation material or composition mainly comprises recycled components. However, fiberglass insulation can harm your respiratory tract if its particles are inhaled. It is precautionary to protect and cover the insulation with a plastic coating. Cellulose insulation has no such complaint. 


A non-combustible composition of insulation makes it stand out from the crowd. You can’t be comfortable under the most pricey one until and unless there’s an authentic claim of fire retardant features. The concept goes strong with the choice of cellulose but for fiberglass insulation, the matter is a bit complex. The material itself is not flammable but fiberglass can break down under extreme heat and even assist a house fire to spread. You can check out our detailed article here on fiberglass flammability. 

Resistance to extreme temperatures

The longevity and effectiveness of insulation material are greatly reliant upon the temperature or climate of its surrounding. The environment of an area induces potential effects on an insulated surface, such as trapping moisture in the case of a humid area or wearing off quickly as the heat surpasses optimal scales. For extremely cold regions, higher R-value insulation is recommended. Cellulose insulation has a higher R-value, which is suitable for cold regions whereas fiberglass works best in almost all moderate climate areas. 


Replaceable insulation is another promising factor that can help you in choosing the insulation of your choice. It allows most homeowners to stick to one type of insulation for years. This is mainly because you can easily replace wear-off insulation with a new one or add some refilling. Usually, cellulose insulation doesn’t allow you to add extra layers or add refills because of a higher weight and R-value. Fiberglass insulation on the other hand is lighter and easy to replace to refill the wear-off areas with time.

Cellulose insulation pros 

  • Eco-Friendly Material 

Cellulose insulation is entirely composed of recycled paper and newspaper. It is estimated to have a 70% composition ratio as compared to other components. The mixture doesn’t undergo heavy bleaching or follow energy-consuming processes. It is added with an additional amount of boric acid making it an effective fire retardant. 

cellulose insulation
cellulose insulation
  • Thermal Resistance 

The R-value for cellulose insulation is although not the highest, but it’s still better than most of the other materials in the market. As mentioned earlier, per inch R-value for cellulose insulation is 3.2-3.5. This R-value provides favorable conditions to keep your home warm during cold weather and vice versa. Thus, a fair R-value can be solely holding back your energy and power bills. 

  • Resistance Against Mold and Mildew 

As discussed before, the mixture of recycled material in cellulose insulation undergoes boric chemical treatment. Ammonium sulfate and boric acid are added in considerable amounts to make the insulation material durable against wear and tear. The major outcome of this composition is increased resistance to pests, mold, and mildew. Hence, this insulation has hypoallergenic properties.  

  • Non-Combustible 

Boric acid and borax are the two key ingredients that make cellulose insulation a classical fire retardant. These chemicals are added to enhance the resistance to fire-catching properties of wooden fibers or recycled paper material used in cellulose insulation. Boric acid and its derivatives constitute about 20% of the total cellulose composition. 

  • Affordable 

The affordability of insulation depends upon the cost taken by the processing or formation along with the components used. Both circumstances are highly favorable and are a compelling reason to install cellulose insulation. The sustainable cellulose insulation is composed of leftovers of paper; that’s quite a treat on the expenditure cost. Moreover, the process of molding the cellulose insulation is also very basic, simple, and doesn’t require long hours to form. 

Cellulose insulation cons 

  • Sagging Material 

Cellulose insulation is heavier than fiberglass insulation and hence it is vulnerable to sag or settle after a specific time. The R-value of cellulose insulation also deteriorates with time as the material starts sagging because of the effect of gravity and a heavier application. Sagging also makes the insulation prone to forming cavities and in return disturbing the entire insulating effect. This problem can be overcome by using wet-spray cellulose insulation. 

  • Moisture Entrapment 

Cellulose or recycled paper in the insulation is prone to trap moisture and humidity. It’s such a nice absorbent that it can seep away a pipeline leakage! Cellulose completely absorbs moisture unlike other forms of attic insulation. It can entrap moisture more than its actual weight. As a result of excessive moisture, cellulose can start settling, sagging, and getting invaded by mold and mildew. Moisture or humidity entrapping makes cellulose insulation less fire retardant as the chemical responsible for it deteriorates. 

Fiberglass insulation pros 

  • Inexpensive 

Fiberglass Insulation is made up of a durable, low-cost material and can last for a long time. Moreover, fiberglass insulation is believed to reduce the energy bill by up to 40%. It is easier to install and can save you money by not requiring any professional application service. 

fiberglass insulation
fiberglass insulation
  • Easy Installation 

Fiberglass is easy to install as it comes in batts and rolls that are handy to take care of. The length and width of these batts and rolls are pre-adjusted to fit any space with standard dimensions. You can also alter the measurements as per the space required. They’re easy to unroll and apply across the entire ceiling. You may not always require professional assistance while insulating your space with fiberglass insulation.

  • Recyclable Material 

The insulation is mostly manufactured using recycled material, glass fibers, and sand. The composition can be easily recycled once discarded. However, the durability and longevity of the composition aren’t compromised by any of the key ingredients of fiberglass insulation.  

  • Moisture Resistance

One of the most competent features of insulation is its moisture resistance. A humid environment or moisture seeping through the roof is to be resisted by the insulation if It’s competent enough. Fiberglass insulation provides a wonderful shield against humid conditions. Hence, it is a top choice of constructors in areas with higher humidity levels. Fiberglass is also an excellent mold and mildew repellent as it doesn’t have room for any of these after fighting away all the vapors! 

  • Fire Resistance and R-Value

Fiberglass insulation possesses non-combustible properties. It contains micro particles of glass and thus, fiberglass insulation is less likely to catch fumes. Though the resistance to heat conduction is relatively less than cellulose insulation, it can be overcome by applying an extra layer of insulation. It is lighter in weight and can be applied in multiple layers.

  • Pests Shielding 

Fiberglass insulation covers the wall and cavities in such a fine manner that there’s a perfectly consistent layer of insulation. Also, it doesn’t usually form cavities and thus, doesn’t allow pests to invade. The material is also not palatable to insects. 

Fiberglass insulation cons 

  • Skin Irritation 

Direct contact with the fiberglass insulation material can irritate your skin and may often cause itching, irritation, and rashes. And if the debris is inhaled, it can affect your respiratory system. Hence, it isn’t safe to apply it on your own without taking safety precautions. 

  • Wear and Tear

If the fiberglass isn’t fixed properly or has gaps and cavities, it can wear and tear gradually. The cavities are prone to allowing air and heat passage and also serve as a staging site for many pests. 

  • Mold Growth 

Fiberglass insulation is observed to catch dust, environmental allergens, and moisture. Unless the fiberglass insulation is entirely covered with a plastic wrap or protective shield, it can trap moisture up to some extent. Hence, mold can easily grow there if you fall short of protecting it.


The list of pros and cons for both types of insulation ends now as we arrive at our final verdict. Cellulose and fiberglass can be on the same pitch in terms of their longevity and resistance against heat conduction. Keeping in view the aspects mentioned earlier, cellulose insulation has a higher R-value quotient if you’re looking for ultimate insulation. It can wear away faster, but not if you have it maintained. Contrarily, if avoiding moisture and easier lightweight insulation is your choice, then fiberglass insulation is for your home.

Charles John

Experienced HVAC technician with 8 years of experience in the industry. Capable of handling all sorts of heating and cooling equipment as well as proficient in operational management, construction-related techniques such as preventative maintenance, electrical troubleshooting and AutoCAD

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