A graphic with closeups of rigid foam board and cellulose insulation transposed next to each other

Cellulose and rigid foam board insulation are two very different types of insulation you can use in your home. However, both have benefits and challenges associated with them you can use to determine which type of insulation is the best fit for you. 

Manufacturers make cellulose insulation from recycled newsprint and denim. It is eco-friendly during its entire life cycle. On the other hand, foam board insulation has a very high R-value and four different types you can customize to your needs. Both cellulose and rigid foam board insulation are great insulation solutions. 

This article will break down cellulose and rigid foam board insulation and directly compare the two types. 

Cellulose Insulation

Cellulose insulation is incredibly eco-friendly. Manufacturers make it using recycled denim, newsprint, and other recycled materials. 

There are three main types of cellulose insulation: loose-fill, dense-packed, and wet-spray. They are all unique in their application and best uses which we detail below. 

Loose-fill 

Loose-fill cellulose insulation is most appropriate for use in attics. However, some homeowners also choose to use it in walls as well. Contractors install it with a blowing machine, though you can complete it as a DIY project if you have some experience and can rent the appropriate equipment. 

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

The typical R-value or efficiency of loose-fill cellulose insulation is about 3.5 per inch of thickness. In addition, it helps to seal any potential cracks or areas where air can get through because you blow it in. 

Dense-Packed

Homeowners and contractors typically use dense-packed cellulose insulation to insulate walls and ceilings. One of the critical benefits of dense-packed cellulose insulation is it does not usually require a vapor barrier.

Dense-packed insulation creates a near-complete seal in the areas you install it. This type of cellulose insulation has a high R-value at around 3.8–4.0 per inch of thickness. 

Wet-Spray 

Wet-spray cellulose creates one of the best seals that insulation can provide. Contractors combine the dry product with adhesive and water immediately before spraying the insulation into place. Because of the application process, wet-spray cellulose works best in new construction instead of renovation projects. 

When this wet paste dries, it seals any cracks or air leakage points where you are installing it. Typically, contractors install wet-spray cellulose insulation before installing the drywall. The R-value for this type of insulation is between 3.6–3.8. 

Pros of Cellulose Insulation

As you probably can tell from the descriptions above, cellulose insulation has several benefits that result in it being one of the most popular types of insulation. 

Eco-friendliness

Cellulose insulation is one of the only types of insulation that is truly eco-friendly. Manufacturers make it using recycled denim and paper. Additionally, the manufacturing process does not create many pollutants. Cellulose insulation is also eco-friendly to dispose of after its lifespan. 

Fire and Mold Resistance

Most types of cellulose insulation have a fire-resistant chemical worked into the insulation itself. This chemical also actively resists mold and prevents potential allergens from entering your home, improving the overall air quality in your home and even slowing the spread of a fire for up to 25 minutes.

High R-Value

Efficiency is one of the main selling points for any insulation, and all three types of cellulose insulation have a high R-value. Dense-packed cellulose insulation has the highest efficiency rating of 3.8–4.0 per inch of thickness. 

Creates a Great Seal

When contractors install any cellulose insulation variety, it fills any cracks or weak spots in your wall, attic, or ceiling. Cellulose insulation creates an excellent seal because it is dense, and all types are sprayed, reaching every nook of an area. 

Great Soundproofing

The density of cellulose insulation and the materials it is made from mean this type of insulation is excellent at soundproofing. It can help limit noises from the outdoors or even between rooms in your home.

Cons of Cellulose Insulation

Cellulose insulation also presents some challenges to consider when deciding which type of insulation to use. 

Cannot Install Yourself

Cellulose insulation requires specialized equipment for installation, meaning it is not DIY-friendly and you will need to hire a contractor to complete the work. 

Short Lifespan

Cellulose insulation only has a 20-30 year lifespan. Some types of insulation have double that. So while cellulose insulation has very high efficiency, its lifespan can be one of its most significant drawbacks.

Sagging

Over time, cellulose insulation tends to sag. In which case, the R-value for the insulation can decrease, and the overall efficiency of the insulation will suffer. Additionally, sagging can cause areas to have less than ideal insulation as it shifts. 

Not a Vapor Barrier

Although dense-packed cellulose insulation does not typically need a vapor barrier, the other types are susceptible to moisture issues.

Rigid Foam Board Insulation

Rigid foam board insulation is quite different from cellulose insulation. Foam board tends to be more structured than cellulose and has a higher R-value

There are four primary rigid foam board insulation types. Each is unique in its properties, benefits, and challenges.

Polyurethane 

There are also four types of polyurethane rigid foam board insulation—rigid foam sheets, spray foam, closed-cell, and open-cell.

Rigid foam sheets are relatively cheap to manufacture and easy to install, which can be done as a DIY project.

Spray foam polyurethane insulation seals incredibly well and reaches nearly every corner of the area you are insulating.

The third type, closed-cell, is sprayed on but dries similarly to the foam sheets.

Finally, open-cell spray foam is not as dense or structurally strong as closed-cell polyurethane. 

The R-value for polyurethane varies based on if it is open or closed-cell. For example, open-cell insulation has an R-value of 3.5 per inch of thickness, and closed-cell insulation has an R-value of 6.0 per inch of thickness. 

Polyisocyanurate 

Polyisocyanurate rigid foam board is solid and rigid. However, it only comes in a rigid board, and manufacturers make it from organic and inorganic materials.

Stacked sheets of polyisocyanurate foam board insulation

Homeowners usually install polyisocyanurate rigid foam boards in roofs, ceilings, and walls. This foam board insulation is excellent in extreme temperatures and can work from 250 degrees Fahrenheit down to -100 degrees Fahrenheit. Polyisocyanurate rigid foam board insulation is highly effective and has R-values between 7.0–8.0 per inch of thickness. 

Extruded Polystyrene Foam

This type of rigid foam board insulation is very effective and robust. It is rigid, has closed cells, and comes as structural panels.

Several pieces of XPS foam board insulation are displayed on a table

Extruded polystyrene has a very high R-value and is excellent at protecting homes from air and moisture. Manufacturers use plastic resin to help build up the strength and durability of this type of insulation—the R-value of extruded polystyrene insulation averages between 4.5–5.0 per inch of thickness. 

Expanded Polystyrene Foam

Expanded polystyrene foam is an affordable yet durable rigid foam board insulation. It is also reasonably lightweight. Don’t let its lightweighted-ness fool you, though—it can handle a fairly heavy load and is quite efficient. In addition, it is bacteria resistant and is good in a wide range of temperatures.

A piece of XPS foam board insulation is applied to the exterior of a building

The R-value for expanded polystyrene foam board insulation is usually between 3.6–4.0 per inch of thickness. 

Pros of Rigid Foam Board Insulation

Rigid foam board insulation has numerous benefits that mostly start with its high R-value and durability.

High R-Value

The least effective rigid foam board insulation type is the average R-value for many other insulation types. And polyisocyanurate rigid foam board insulation has an R-value of 7.0 to 8.0 per inch of thickness. 

Different Facings

Different facings can help increase specific properties of the insulation. Some facings that manufacturers use include plastic, foil, or aluminum and might help manage moisture and improve the R-value. These facings can also allow homeowners to install foam board insulation underground.  

Structurally-Beneficial

Rigid foam board insulation offers great structural properties that can help with structural integrity and durability wherever you install it. 

Extensive Temperature Range

Certain types of rigid foam board insulation can be effective across large ranges of temperatures. This range means you can use them even in locations with extreme weather. Additionally, they are practical to use under roofing susceptible to extreme temperature swings. 

Cons of Rigid Foam Board Insulation

Rigid foam board insulation does have some drawbacks, however.

Seams

Because rigid foam insulation is a physical board, it is necessary to tape up the seams to ensure no airflow works its way between the boards. Taping must be done correctly, or the seams can cause inefficiencies in the insulation. 

Not Environmentally Friendly

Manufacturers use hydrochlorofluorocarbons (HCFCs) when making rigid foam board insulation. The manufacturing process itself is not environmentally friendly. Neither is the material itself nor its disposal at the end of its lifespan. 

Decreasing R-value

The R-value for rigid foam board insulation can start decreasing as early as two years after installation. While it is durable, the slowly diminishing R-value can cause inefficiencies, especially toward the end of the insulation’s lifespan. 

Affected by Sunlight

Sunlight can damage rigid foam board insulation. A  lot of damage can be done even with short-term storage in sunlight. Therefore, it is essential to properly hold the rigid foam board to prevent damage. 

Direct Comparison

Below is a chart directly comparing cellulose and rigid foam board. The chart should help you visualize the similarities and differences between the two types of insulation. 

CriteriaCelluloseRigid Foam Board InsulationVerdict
R-Value 3.5 to 4 per inch of thickness3.5 to 8 per inch of thickness (varies by)Rigid foam board insulation has a better R-value and is overall more effective. 
Moisture ResistanceSusceptible to moisture damage and saggingSome types are susceptible to moisture damage.Rigid foam board insulation is typically better at resisting moisture. 
Durability 20-30 years100+ yearsRigid foam board insulation has a very long lifespan. 
InstallationRequires a professional to installSome types can be done as a DIY. Most require a professional.The two types are fairly equal in their installation requirements. 
Cost$0.80 to $1.75 per square foot$1.20 to $1.45 per square footThe costs are similar between the two types of insulation.
Vapor Barrier It cannot act as a vapor barrierSome types require a vapor barrier.It is the better choice depending on the type of rigid foam board insulation. 
Soundproofing Good for soundproofingOk, for soundproofing. Some sound still goes through it.Cellulose is better for soundproofing. 

Conclusion

Both cellulose and rigid foam board insulation offer a lot of value for your home.

Cellulose is environmentally friendly, creates a great seal, is fire and mold-resistant, and is excellent at soundproofing. On the other hand, rigid foam board insulation has an incredibly long lifespan and a high R-value.

So, depending on what you are looking for, both cellulose or rigid foam board insulation could be an excellent solution. 

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