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Which is the Best Loose Fill Insulation: Cellulose or Fiberglass?


Is it time to replace or add insulation to your home? If so, how do you know which is the right loose fill insulation material for your home and needs? The two most commonly used residential loose fill insulation materials are fiberglass and cellulose. While cellulose and fiberglass do have some similarities, each of these materials has their own advantages and disadvantages. In this article, we will be comparing which is the best loose fill insulation: cellulose or fiberglass.  So, when the time comes to insulate your home, you can make the most informed decision.


Both cellulose and fiberglass insulation are relatively inexpensive materials. In fact, the cost of these two materials is so similar that any price difference you encounter could be a result of the contractor you choose. Some contractors may have access to special deals or discounts but overall, fiberglass and cellulose are generally the most inexpensive insulation materials on the market. 


Fiberglass is one of the most popular insulation materials due to its effectiveness and affordable price. Technically, fiberglass is easy to install and can be done without proper training or equipment. However, it is always best to hire an experienced insulation contractor because if fiberglass insulation is improperly installed, it will not do its job adequately. On the other hand, installing cellulose requires special and sometimes expensive equipment like high-powered insulation blowers, which require technical experience to use.


Fiberglass and cellulose insulation have very similar R-values (between 3.5 and 3.7 per inch). However, this varies on a few factors, such as the climate of the region they are installed in. Generally speaking, however, the R-values of cellulose and fiberglass are very closely tied.  

Air Leakage

Neither cellulose or fiberglass insulation act as an air barrier (although both help retain heat). Both cellulose and fiberglass insulation allow air to pass through and therefore they both need to be paired with some type of air barrier. Fiberglass in particular is more affected by air flow than cellulose. Cellulose slows air flow, while fiberglass does not.

Fire Resistance

Fire resistance is where fiberglass and cellulose begin to differ somewhat. Fiberglass is comprised of spun glass; therefore, it will not burn at any normal temperature. If in contact with a direct flame, it will simply melt. Cellulose, on the other hand, is made of ground up paper, making it quite flammable. Modern cellulose, however, is heavily treated with flame retardants that also minimize pest infestations. Thus, with modern cellulose, flammability is no longer a major concern.


Regions that experience extremely cold weather may opt to choose cellulose as their insulation material of choice. This is because during freezing weather, heat is quickly stripped from fiberglass insulation, and the R-value of fiberglass insulation reduces. Cellulose, on the other hand, does not suffer as much from this problem.

So … Which Insulation is Best – Fiberglass or Cellulose?

As you can see, fiberglass and cellulose insulation are quite similar. In terms of popularity, fiberglass is the most commonly installed insulation. However, cellulose is a close second. So, which should you choose for your home? At the end of the day, the choice is yours when it comes to choosing the best insulation for your home. Due to the similar nature of both materials, it really is dependent on the project at hand. For this reason, we always advise you speak with and hire a professional insulation contractor who will be able to provide you with reliable, trustworthy and professional advice. They will be able to look at the unique needs of your home and offer you advice based on your specific requirements. 

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Topics: Insulation, Fall