What is R-Value, and why does it matter if you want to improve your home’s energy efficiency and comfort? The “R” in R-value stands for resistance, i.e., how well insulation in your home resists heat flow. The higher the number, the better; higher values indicate better insulation performance. 

Whether assessing existing insulation or planning a new installation, knowing how to determine R-value can help keep your home properly insulated.

What Is R-Value?

R-value measures thermal resistance, which indicates how well a material insulates. The higher the R-value, the more the insulation reduces heat transfer. This rating matters the most for attic insulation, as proper attic insulation can significantly impact a home’s energy efficiency. Do you remember how your Mom yelled at you to wear a hat outside in the cold to keep heat from escaping? Your attic is your home’s hat. 

For homeowners, learning about R-value will give you the knowledge to make an informed decision when comparing different insulation materials and determining whether your home has adequate insulation for where you live.

How to Calculate R-Value

Homeowners can easily calculate the R-value of existing insulation themselves. The simple process involves identifiying the type of insulation in your home and then measuring its thickness in inches. Multiply the thickness by the R-value per inch for the kind of insulation (search online if unsure). 

For example, if you have 10 inches of fiberglass batt insulation with an R-value of 3. 1 per inch, the total R-value would be 10 x 3. 1 = R-31.

Understanding Different Insulation Types

Different insulation materials have varying R-values per inch, which impacts their effectiveness. Remember that you don’t always want the highest R-value on the market; it could be overkill and a waste of money in a mild climate. 

Fiberglass Insulation

Fiberglass insulation is popular due to its cost-effectiveness and availability. It comes in two main forms: blown and batts.

  • Blown Fiberglass: This type’s R-value generally ranges from 2. 2 to 2. 9 per inch. It’s often used in attics and hard-to-reach areas because it can easily fill in around obstructions. As its name implies, it’s blown into the space through tiny holes cut in the walls. 
  • Batts Fiberglass: These are pre-cut insulation panels with R-values between 2. 9 and 3. 8 per inch. Batts are ideal for standard wall framing and are simple to install. They’re easier to install in new construction or a remodel when you take the walls down to the studs. 

Cellulose

Cellulose insulation from recycled paper products blown into attics and walls boasts an R-value of 3. 1 to 3. 8 per inch. It’s known for its eco-friendly composition. Its density allows it to reduce airflow, making it effective for minimizing thermal bridging. 

Rock Wool

Rock wool, also called mineral wool, has excellent fire resistance and soundproofing qualities. Generally, it has an R-value between 2. 2 and 3. 3 per inch. Due to its robust nature, it’s suitable for both thermal insulation and soundproofing.

Foam Insulation

Foam insulation is available in both sprayed and rigid board forms. It’s particularly effective when your goal is to trap heat inside your home due to its high R-values per inch, which range from 3. 6 to 8. 2. Foam insulation is often used for air sealing, as it expands to fill gaps and cracks and offers excellent thermal resistance.

These values can vary slightly depending on the specific product and brand. When calculating the R-value, whenever possible, use the exact specifications provided by the manufacturer.


The recommendation as an R-value for insulation in your home will depend on your climate zone. Generally, you’ll want a higher R-value in a colder climate to maintain comfortable indoor temperatures and energy efficiency. Here are some guidelines:

  • Warm climates: R-30 to R-49
  • Moderate climates: R-38 to R-60
  • Cold climates: R-49 to R-60

To determine the appropriate insulation thickness to install, divide the recommended R-value by the R-value per inch of your chosen insulation material. For instance, in a moderate climate aiming for R-49, you would need about 16-22 inches of blown fiberglass insulation.

Factors Affecting Insulation Performance

While R-value is a crucial factor in insulation effectiveness, it’s not the only thing that impacts the overall performance of your home’s insulation.

Air Sealing

Before adding insulation, address any air leaks in the attic or room where you’re putting insulation. Reducing or eliminating leaks enhances insulation performance and prevents moisture issues that could degrade the insulation over time. If the insulation gets wet regularly, eventually, it will break down. And damp insulation isn’t effective at blocking heat leakage. 

Air leaks can also lead to drafts and higher energy bills. When you seal gaps and cracks, you improve both the insulation’s effectiveness and indoor air quality.

Installation Quality

The insulation won’t perform at its rated R-value if the installer doesn’t get it right. Gaps between the insulation, compression, or moisture can significantly reduce effectiveness. Improper installation can lead to thermal bridging, which is when heat bypasses the insulation due to air gaps. Hiring a professional to install your insulation ensures it fits snugly and provides the expected thermal resistance.

Insulation Settling

Some types of insulation, particularly a blown-in variety, may settle over time, reducing their effective R-value. You’ll want to account for this settling when calculating long-term insulation performance. Reassessing insulation over time ensures that its R-value remains consistent and reliable.

How to Assess Existing Insulation

For homeowners wondering about the state of their current insulation, you can analyze its current effectiveness simply. 

First, find a saw way to access the attic or area where you have insulation. Use a ruler or tape measure to measure the depth of the insulation. Then, identify the type of insulation and use the R-value per inch for that type to calculate the total R-value. Look up your climate zone and compare your R-value to the recommendation for where you live.

If the calculated R-value is below the recommendation, consider adding more insulation to improve energy efficiency. 

Choosing the Right Insulation

When selecting insulation, start with your climate zone and its recommended R-value. This way, you can constrict your potential options within that range. Look at the space available for insulation, whether it’s the thickness of existing walls or the planned thickness of a new build. Any insulation type you choose will have to fit in that space. 

Since different insulation types vary in cost, compare your options to your budget. Most homeowners must balance performance with affordability to find an effective solution that fits their budget. Installing the insulation yourself will save you money, but it may not be as precise and effective as a professional installation. 

If you’re concerned about the environment, you can also opt for eco-friendly insulation materials, which may have lower environmental impacts.

The Impact of Proper Insulation

Adequate insulation can significantly impact a home’s comfort and energy bills. Properly insulated homes maintain more consistent indoor temperatures, improving overall home comfort. It decreases the workload on your HVAC system and reduces heating and cooling costs.

Insulation also reduces noise pollution from outside, adding soundproofing and enhancing inhabitant comfort. Investing in insulation can lead to substantial long-term savings and increase your home’s value.

When to Consult a Professional

While determining the R-value can be a do-it-yourself task, sometimes when you might want to consult a professional. Older homes could contain asbestos insulation, you don’t want to risk it if you’re unsure. The same applies if you suspect mold or moisture issues in your insulation, as both can be a health hazard. If you’re planning a major insulation upgrade, talk to a pro. 

Many heat and energy companies offer a free home audit. Professional energy auditors can provide a comprehensive assessment of your home’s insulation needs and recommend the most effective solutions. They also might know of rebates and subsidized programs to upgrade your insulation. 

Final Thoughts About Determining R-Value of Insulation

Understanding and determining the R-value of insulation empowers you to make informed decisions about your home’s energy efficiency and comfort. If you know how to assess existing insulation and choose the right materials for an upgrade, you can significantly improve your living environment while potentially reducing energy costs.

Whether tackling a do-it-yourself project or working with professionals armed with knowledge about R-values, you can ensure your home keeps your family warm and cozy for years to come.


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Danny Lipford

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Danny Lipford is a home improvement expert and television personality who started his remodeling business, Lipford Construction, at the age of 21 in Mobile, Alabama. He gained national recognition as the host of the nationally syndicated television show, Today's Homeowner with Danny Lipford, which started as a small cable show in Mobile. Danny's expertise in home improvement has also led him to be a contributor to popular magazines and websites and the go-to source for advice on everything related to the home. He has made over 200 national television appearances and served as the home improvement expert for CBS's The Early Show and The Weather Channel for over a decade. Danny is also the founder of 3 Echoes Content Studio, TodaysHomeowner.com, and Checking In With Chelsea, a décor and lifestyle blog.

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