Cellulose Insulation vs Spray Foam Insulation

All about their pros and cons, areas of use, and more

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When you find pests in your home, it is always not good news. Pests, both insects and rodents, are not only disgusting and irritating with all the noise and disturbance they produce. They are also the source of unpleasant smells and damage like chewed wires. In addition, these critters can also cause damage to your pipes, as well as transfer different diseases!

This is why homeowners who have pests in the attics often search for insulation to protect their homes. In this article, we will tell you about insulation that repels rodents and bugs. You will learn what types of this insulation are considered the most popular ones. Also, we will explain the major distinctions and finish the cellulose insulation vs foam insulation competition!

With the help of this information, you will be able to choose the type of home insulation that will suit your specific needs. And of course, you will be more knowledgeable in its types such as best insulation for rodent control or rat-proof insulation.

Not just insulation, but a shield against pests.
By vista.com

Foam Insulation vs Cellulose Insulation. Basic Distinctions

Quite many homeowners get puzzled because they don’t know what type of insulation to use for repelling rodents and insects. Moreover, not all people know that insulation can actually work as a protective shield against bugs, mice, and rats!

If you realize you need to use pest-resistant insulation in your home, you will sooner or later face a complicated question: which type of insulating material, cellulose vs foam insulation, is better and why? The task becomes even more difficult to solve because both types of insulation will stop bugs and pests from both getting into your home and spreading around it:

When it becomes apparent that pest-resistant insulation is a necessity in your home, the challenge that arises is selecting the best insulating material. The main cellulose insulation vs spray foam debate surfaces, leaving many perplexed. This is because both forms of insulation promise to halt the invasion and proliferation of pests in your home.

Fortunately, you can find a thorough breakdown of each insulation type further in this article. This will empower you to grasp how each type operates and assess whether it aligns with your specific needs. Whether it's spray foam vs blown in insulation or the main cellulose insulation vs spray foam, understanding these options will lead to an informed decision that best suits your home's insulation requirements.

Cellulose Insulation

Cellulose insulation is considered to be the most effective and thus popular insulation type among many homeowners. It is primarily made of recycled plant materials, often up to 80 percent, including post-consumer paper. 

The other 20 percent of cellulose insulation are sometimes acrylic binders, but in the majority of cases, it will be different chemicals that are used to make the insulation fire-retardant. One of the most commonly used chemicals is boric acid.

Why is boric acid added to cellulose insulation, you may be wondering? See, this chemical gives the insulation its fire-retardant purposes. And since boric acid is a rather weak acid, its presence in cellulose insulation is not dangerous for your health.

Now, how does this acid work? When an insect or a rodent consumes boric acid, the chemical goes straight to the creature’s stomach. The bug’s/rodent’s nervous system usually feels the effects of the acid first, and then death follows pretty soon after.

However, cellulose insulation prevents pests not only because it contains boric acid. Cellulose is also very effective at blocking any damaged seals and other openings that small critters and insects can use as entry points to get into your home.

Spray Foam Insulation

Unlike the previous insulation type, spray foam insulation is made of isocyanate and polyol resin. These compounds provide proper bonding and can make spray foam rigid. Usually, spray foam insulation comes in two types:

  • Open-cell spray foam
  • Closed-cell spray foam

Open-cell spray foam is softer. In addition, it can take the shape of the area you spray it in. This feature makes this type of insulation a great choice if you need to seal very small and narrow or curved areas and corners. It will also be an optimal choice for odd-shaped parts of an attic or basement.

Closed-cell spray foam can also be used to close the gaps around your windows, doors, and other openings that may let pests in. But unlike open-cell insulation, this one is more rigid due to its lack of moisture. And even though closed-cell spray foam is durable, it can’t be used the same way you use open-cell spray foam, since it dries hard!

Now you know the basic distinctions of spray foam vs cellulose insulation. However, this is just a brief comparison and to be able to decide which type of insulation you might need for your specific purpose, we suggest you read on and find out how each of these insulation types would work for different areas in your home.

Foam Insulation vs Cellulose Insulation Use

Before you start installing any type of insulation, not only cellulose or blown one, you should define what the purpose of its use would be. Depending on where in your home you are planning to install it and what for, you might want to consider different insulation types.

Below, we will explain the nuances of insulation areas of use in the most common spaces of your house such as:

  • Attic
  • Existing walls
  • Floors
  • Walls without sheathing

But before you proceed reading, you should answer the following questions regarding insulation installation:

  • Where in your home you are going to install it? Is it going to be the attic, basement, crawlspace, floor, bonus room floor, garage ceiling, etc.?
  • What is your overall goal for the insulation installation project?
  • Where is the house most uncomfortable, and at what season of the year?
  • Where are your HVAC equipment and air duct system(s) located?

When you answer these questions, you will be able to easier define what type of insulation you might find more suitable for your needs.

Spray Foam vs Cellulose Insulation For Insulating Floors 

If you need to install floor insulation, spray foam is absolutely the best option you can find! And in fact, it doesn’t even matter what project you are up to. It can be an outdoor deck that you want to convert into living space, or basement ceiling, or the subfloor over a damp crawlspace! 

In any case, use spray foam insulation. You just need to make sure that it is a two-pound, closed-cell spray. Closed-cell spray foam insulation performs as a:

  1. Thermal barrier
  2. Air-infiltration barrier
  3. Moisture barrier
  4. Structural Improvement

Spray Foam vs Cellulose Insulation For Existing Wall 

If you need insulation for existing walls that are sheathed with sheetrock or paneling, you have two options to choose from:

  1. Low-expansion insulation foam
  2. Drill-and-Fill dense-pack cellulose

Let’s see what each of them is. Low-expansion foam is a product taht is different from spray polyurethane foam. It is actually a liquid with the properties of shaving cream, that is pumped into the wall cavities. After being applied, it spreads throughout the cavity, filling the voids.

Drill-and-Fill dense-pack cellulose is another option you can use. Check out what features this one has:

  • Like low-expansion foam, it is pumped into the walls through a small hole, filling all the voids
  • It is also a sound deadening product
  • It is excellent as an exterminator’s product
  • It can be used for garage ceilings that are sheathed with sheetrock to fill the empty voids found in the floor system between a bonus room and the garage

Spray Foam vs Cellulose For Walls Without Sheathing

For insulating the walls without sheathing, where the studs are exposed, you also have two insulation options to choose from:

  1. Spray foam insulation
  2. Cellulose insulation

If you need to learn more about them, just read the beginning of the article. We have described their major features there.

Spray Foam vs Cellulose For Attic Insulation

The decision between main cellulose insulation vs spray foam is one of the key dilemmas homeowners face. 

If you need to insulate your attic and the HVAC equipment and air ducts are located there, it is better to install spray foam insulation. In particular, you need the one with open cell spray foam to protect the equipment and ducts. 

However, if your attic doesn’t have any HVAC equipment or air ducts, you should install regular cellulose installation.

Now you know about the major distinctions between the two most common insulation types, which are cellulose insulation and spray foam insulation. We gave you the basic information on each of them and also, you learned what type of insulation should be used depending on the area you are planning to insulate in your home.

With all this in mind, you will now be able to make your home warmer, better protected, and of course, pest-resistable - all withh the help of insulation. Also, note that insulation can typically be installed yourself. However, some types of it need professional treatment! So you’d better ask a professional for advice before you start your project. And should you decide to hire professionals, make sure the contractors are experienced and qualified!


Let's delve into some record-breaking facts in the world of insulation:

  1. Greatest Energy Savings: In 2012, a net-zero energy home in North Carolina, USA, reported an impressive 60% reduction in energy costs after using high-quality spray foam insulation. This is one of the highest energy savings ever reported for a residential building. The house was part of a study by the U.S. Department of Energy's Building America Program, highlighting the remarkable efficiency of spray foam.
  2. Largest Building Insulated: The renovation of the Pentagon, one of the world's largest office buildings with over 6.5 million square feet of space, involved the use of cellulose insulation. As part of the renovation, completed in 2011, cellulose was chosen for its fire-resistant properties, ability to block air infiltration, and its high R-value per inch.
  3. Record for Retrofitting: In 2010, the Empire State Building underwent a major retrofit to improve its energy efficiency. Spray foam insulation was part of this retrofit, contributing to the building’s 38% reduction in energy consumption, the highest ever recorded for a retrofit of a building of this scale.
  4. Innovation in Insulation: In terms of product innovation, Icynene, a leading manufacturer of spray foam insulation products, broke records in 2007 by introducing a 100% water-blown light density spray foam insulation. This product is unique in that it completely eliminates the use of ozone-depleting blowing agents, thus setting a high standard for eco-friendly insulation materials.
  5. Longevity Record: As far as durability is concerned, the record goes to closed-cell spray foam insulation, with a lifespan extending beyond 80 years. This longevity surpasses that of many other insulation materials, making it an investment that stands the test of time.

These records illustrate the significant role both cellulose and spray foam insulations play in improving energy efficiency, reducing carbon footprints, and preserving architectural landmarks.


Here are some factual insights regarding cellulose and spray foam insulation:
  1. Energy Savings: Spray foam insulation has shown to provide energy savings of up to 50% or more, significantly higher than traditional types of insulation like cellulose, which typically yield around 30% in energy savings.
  2. Insulation Use in US Homes: According to the U.S. Department of Energy, about 80% of homes in the United States built before 1980 are under-insulated. Among those that are properly insulated, cellulose insulation is used in approximately 7% of U.S homes, while spray foam is used in about 12%.
  3. Effectiveness: In terms of R-value, which measures an insulation material's thermal resistance, spray foam typically ranges from R-3.5 to R-6.5 per inch of thickness, depending on the specific product. Open-cell spray foam is on the lower end, while closed-cell spray foam is on the higher end. Cellulose insulation, on the other hand, has an R-value of about R-3.2 to R-3.8 per inch.
  4. Costs: When it comes to costs, cellulose insulation is often less expensive upfront. The average cost to install cellulose insulation is between $1.50 and $3.50 per square foot, while spray foam insulation costs between $1.25 and $3.25 per square foot for open-cell spray foam, and between $1.75 and $3 per square foot for closed-cell spray foam.
  5. Longevity: Both types of insulation are designed to last a long time, but spray foam, particularly the closed-cell variety, tends to have a longer lifespan. It can last more than 80 years with proper maintenance, while cellulose insulation typically lasts around 20 to 30 years.


Here are some fact-based comparisons that highlight the key differences between cellulose and spray foam insulation:
  1. R-Value: The R-value, a measure of insulation's thermal resistance, varies between these two insulations. On average, spray foam insulation has an R-value of around 6.0 per inch for closed-cell and 3.5 per inch for open-cell, while cellulose insulation has an R-value of approximately 3.2 to 3.8 per inch. This indicates that spray foam often provides superior thermal resistance.
  2. Fire Resistance: While both types of insulation are fire-resistant, cellulose is treated with more fire retardants. It is approximately 55% more fire-resistant than spray foam, making it a safer option in the event of a fire.
  3. Pest Resistance: Both insulations offer some level of pest resistance. However, cellulose insulation is often treated with borates, which deter pests like insects and rodents, giving it a slight edge in pest resistance.
  4. Air Sealing: Spray foam insulation has superior air-sealing properties. When applied, it expands to fill gaps and cracks, effectively preventing air leaks. In contrast, cellulose insulation does not provide the same level of air sealing, potentially allowing for drafts and energy loss.
  5. Moisture Control: In terms of moisture control, closed-cell spray foam insulation outperforms cellulose. It provides a moisture barrier, preventing condensation and the potential growth of mold and mildew, which cellulose insulation cannot do.
  6. Environmental Impact: Cellulose insulation is often hailed as the more environmentally friendly option. It's made from up to 85% recycled paper products, whereas spray foam is a synthetic material.

These comparisons underline that the choice between spray foam and cellulose insulation depends on several factors, including the specific needs of the building and its occupants, environmental considerations, and budget.

Frequently Asked Questions

How Often Shall I Change My Insulation?

Insulation shall be changed every 15-20 years depending on the type of insulation.

Shall I Remove Old Insulation?

Expert contractors advise that removing old fiberglass insulation is best before installing new cellulose insulation because of possible mildew, mold, or rodent excrement.

Is It Possible To Have Too Much Insulation?

Yes, it's possible to over-insulate an attic or another place, but it will cause moisture buildup and eventually result in mold. 

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