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What Is Insulation R-Value?

If you are considering ways to increase the energy efficiency and performance of your home, insulation should certainly be on your list of potential solutions. There are plenty of things to consider as you research insulation, and perhaps the biggest factor is the R-value. So, what exactly is insulation R-value and how does it affect performance? Here’s what you should know.

What Is Insulation R-value?

Simply put, the R in insulation R-value indicates resistance—this is used as the basic measurement of the heat resistance of the insulation material and is calculated per inch of width. Here’s an example:

How Is Blown Fiberglass Insulation R-Value Calculated?

Let’s start with an example: solid wood has an R-value of 1. An R-value is also calculated per inch of width. Therefore, a three-inch-thick board has an R-value of 3. Blown fiberglass installed in the attic has an R-value of 2.2 per inch, so 12 inches of it would give you an R-value of 26.4 in your attic installation project.

How Much Insulation Do I Need?

There are a variety of factors that can affect the specific amount of insulation you will need for your home, including:

  • Regional location
  • Type of heating and cooling system you have in your home
  • Size and age of your home
  • Areas of your home that need insulation
  • And more

The most influential factor for how much insulation you will need will be your regional location. Consulting with an experienced professional can help you determine exactly what type, and how much insulation will work best for your home and needs.

What Are the Recommended R-Values for the Chicago Area?

Map of insulation zones around the United States

Chicago is in Zone 5, so ENERGY STAR recommends the following:

  1. For an un-insulated attic, you will need an R-value of 49-60
  2. For areas with 3-4 inches of existing insulation, you will need an R-value of 38-49
  3. For insulating flooring, you will need an R-value of 25-30

Of course, these recommendations are merely estimates, so it’s important to consult with a professional who can properly inspect your home and any existing insulation to identify your specific needs and offer a variety of budget-friendly solutions.

Types of Insulation

Depending on the area you live in, and the areas in your home that need insulation, will determine which type of insulation will work best for your home. Here are some of the most common types of home insulation and where they work best.

  • Fiberglass – available in blown-in and batting form, fiberglass is most often used in attics but works well in walls and crawl spaces.
  • Radiant Barrier – designed as a reflective insulation material, radiant barrier is typically installed under the roof in attics to reduce cooling costs.
  • Spray Foam – applied as a wet material, this type of insulation expands into a thick foam to fill small gaps and crevices in hard to reach areas. Typically installed in attics and wall cavities.
  • Cellulose – environmentally friendly alternative consisting of as much as 85% recycled materials that works well in all areas of the home.

Insulation Contractors in the Chicago, IL Area

Need help deciding what insulation is best for your home? ThermaSeal / Lakeside can help! Give us a call today at 800-836-2535 or contact us online.

Products We Install

Our team installs both batt and blown-in fiberglass insulation.


Help prevent mold and excessive moisture infiltration in homes you build with our waterproofing services.

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