Cellulose Insulation R-Value: What to Know

If you’re looking for the perfect home insulation, you’ve probably discovered two elements of the insulation trade—cellulose insulation and R-values. 

But What is cellulose insulation and what does an R-value mean? In this guide, we’ll explore everything you need to know about both. We’ll describe the concept of heat resistance, explain R-values, and break down numerous details about cellulose insulation R value and more. We’ll also explore other attic insulation product options that might be a good fit for your home. 

What is Resistance?

An R-value refers to the ability of insulation (or other insulation materials) to resist one or more of the three types of heat energy:1

  • Convection
  • Conduction
  • Radiation

Home insulation products typically provide resistance against convection and conduction, while radiant barriers reduce the impacts of radiant heat.

A higher R-value indicates a higher resistance—for example, an R50 product provides significantly higher heat resistance than an R30 product. 

Why does this matter? The more resistance your insulation product provides, the more control you have over the heat transfer in your home. You want to achieve as high resistance as possible to:

  • Keep heat from the attic from infiltrating your conditioned spaces in the summer
  • Prevent heated air from escaping into the attic in the winter

Calculating R-Value

So, how is R-value measured? Insulation manufacturers measure R-value with a somewhat-complicated formula:2

R-value = Temperature (°F) x hours x square feet/BTU (British Thermal Units)

Practically speaking, insulation and building professionals use R-values to determine how thick insulation should be to achieve a certain level of resistance in an insulated space (an attic, the spaces between walls or stories, or a crawl space). 

For instance, if an insulation professional wants to achieve R30 (in theory) with an insulation product that provides R5 per inch of thickness, they’ll need to install enough product to reach 6 inches of depth.3

But, there are a few important things to consider about R-values:

  • The R-value of a space isn’t directly proportional to insulation thickness—the formula includes numerous other factors like the temperatures the insulation type will have to resist.
  • The insulation R value can change under certain conditions, like:
      • Normal wear and tear with age
      • Compression from storage boxes or walking
      • Settling over time
  • R-Value isn’t the only factor to consider when choosing an attic insulation product. You should also pick an option that aligns with your:
      • Budget
      • Desired longevity
      • Application or installation location
      • Local climate

Cellulose Insulation: R-Value and More

Now that you know more about R-values, let’s explore them in relation to cellulose insulation. 

How is Cellulose Insulation Installed?

Cellulose is only available in blown in insulation (also called loose-fill). To install this type of insulation, professionals:

  1. Don their safety gear and clear an attic space, removing:
      1. Old insulation
      2. Storage boxes
      3. Pest debris
      4. Dust and dirt
  2. Clear the path to the installation access point 
  3. Use a specialized blower system to cover the entire surface in cellulose
  4. Review the entire space to ensure complete coverage and adequate thickness

What is the R-Value of Cellulose Insulation?

Cellulose insulation R value per inch is variable, but most cellulose insulation products offer R3.5-R3.7 per inch.4

So, if you need to reach R30 in your attic, you’ll need a significant thickness—anywhere from 8.1 to 8.6 inches of depth. 

But, remember that you’ll have to take care to maintain that R-value throughout the life of your insulation. Since cellulose insulation can lose some of its resistance when compressed, do your best to prevent compression by:

  • Walking on your insulation as little as possible in attic spaces
  • Avoiding piercing the insulation when you drill into walls
  • Placing storage boxes in closets instead of on top of the insulation in your attic

Benefits and Drawbacks of Cellulose Insulation

Cellulose vs fiberglass insulation is quite comparable in terms of R-value, and its only significant advantage over other insulation types is its sustainability—cellulose is typically made from recycled paper, but in many cases, fiberglass is also made from recycled material.5

Blown cellulose insulation does, however, have drawbacks:

  • It’s more prone to mold growth than fiberglass.
  • It’s usually more expensive than fiberglass.
  • It creates significant dust during installation.
  • It requires specialized equipment to install.

Choosing the Best Insulation Product for Your Home

Cellulose insulation isn’t your only choice—you should also consider:

  • Different insulation types in addition to blown-in, like:
    • Batt (or roll) insulation
    • Sprayed insulation
  • Other insulation materials aside from cellulose, including:
    • Fiberglass
    • Mineral wool
    • Liquid foam

Blown-in insulation R-value, batt R-value, and spray R-value depend on various factors, including the material used for the chosen type. Understanding the difference between blown in insulation vs spray foam insulation or cellulose vs fiberglass, is important so you can choose the best method for your home.

However, the most commonly used insulation material in residential applications is fiberglass batts—this method is cost-effective, time-tested, and appropriate for numerous applications. 

Attic Construction Can Help Decrease Your Home Energy Costs

Cellulose insulation provides adequate R-values per inch compared to its counterparts in the insulation industry—but R-value isn’t the only important factor when choosing the proper insulation type for your home. 

With so many options, how do you make the best choice? The experts at Attic Construction can help you get your insulation right the first time—our team of experienced professionals will help you choose the best product, install it safely, and maintain its efficacy for years to come. 

Whether you’re in search of attic cleaning in Orange County, or Phoenix insulation installation, Attic Construction is the attic brand of choice. We can’t wait to help you optimize your attic space and reduce your home energy use. 



  1. US Department of Energy. Insulation. https://www.energy.gov/energysaver/insulation 
  2. ScienceDirect. R-Value. https://www.sciencedirect.com/topics/engineering/r-value 
  3. Home Depot. All About Insulation R-Values. https://www.homedepot.com/c/ab/insulation-r-values/9ba683603be9fa5395fab9091a9131f 
  4. HomeAdvisor. Comparing the Pros and Cons of Cellulose and Fiberglass Insulation. https://www.homeadvisor.com/r/cellulose-vs-fiberglass-insulation/ 
  5. US Department of Energy. Types of Insulation. https://www.energy.gov/energysaver/types-insulation 

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