Insulation R-Value Chart: R-Values Per Inch (For 51 Materials)

When thinking about insulation, the key metric you have to think about is the insulation R-value. As we have talked about in the post about types of insulations here different materials and types of insulations have different R-values. To help you choose adequate insulation, we have summarized the R-values of 51 most common insulation materials (check the insulation R-value chart below).

The range of R-values of insulation materials spans from materials with R-10 insulation values per inch like vacuum insulated panels and silica aerosol to below R-1 values per inch like bricks, glass, and poured concrete.

Here is the key thing:

When comparing the thermal resistance of insulation materials, you have to compare R-values per inch of thickness. That means that the insulation R-value chart you will find below is basically an insulation thickness chart, based on 1 inch of insulation.

Example: Fiberglass batt has a typical R-value of R-3.7 per inch of thickness. That means that if we were to use 4-inch fiberglass batts, the overall R-value would be R-14.8.

r-value per inch in attic
Example of applying R-3.7 per inch fiberglass batts on attic walls and blown-in insulation on the attic floor (typical R-value of R-2.7 per inch).

To help you out determine what is the R-value of insulation materials with thickness over 1 inch, we have included R-values for:

  • 2-inch thickness. Example: Closed-cell spray foam has a typical R-value of R-6 per inch. That means that 2-inch closed-cell spray foam has an insulation R-value of R-12.
  • 4-inch thickness. Example: High-density EPS has a typical R-value of R-4.2 per inch. That means that 4-inch EPS has an insulation R-value of R-16.8.
  • 8-inch thickness. Example: Phenolic rigid panel has a typical R-value of R-4.5 per inch. That means that an 8-inch phenolic rigid panel has an insulation R-value of R-38.

You can find all of these insulation R-values per inch and per 2, 4, and 8 inches in the following insulation R-value chart:

Note: Below the table, we address some of the key questions regarding these insulation R-values like what is the best R-value, . You can also use the comment section if you don’t find your answer and we will try to help you out.

Insulation R-Value Chart (Per 1, 2, 4, 8 Inches Thickness)

Insulation Material: R-Value Per Inch: 2 Inch R-Value: 4 Inch R-Value: 8 Inch R-Value:
Vacuum Insulated Panel (VIP) R-25 Per Inch R-50 R-100 R-200
Silica Aerosol R-10.3 Per Inch R-20.6 R-41.2 R-82.4
Polyurethane Rigid Panel (CFC/HCFC Expanded) New R-7.5 Per Inch R-15 R-30 R-60
Polyurethane Rigid Panel (CFC/HCFC Expanded) After 5-10 Years R-6.25 Per Inch R-12.5 R-25 R-50
Polyurethane Rigid Panel (Pentane Expanded) New R-6.8 Per Inch R-13.6 R-27.2 R-54.4
Polyurethane Rigid Panel (Pentane Expanded) After 5-10 Years R-5.5 Per Inch R-11 R-22 R-44
Foil-Faced Polyisocyanurate Rigid Panel (Pentane Expanded) New R-6.8 Per Inch R-13.6 R-27.2 R-54.4
Foil-Faced Polyisocyanurate Rigid Panel (Pentane Expanded) After 5-10 Years R-5.5 Per Inch R-11 R-22 R-44
Closed-Cell Polyurethane Spray Foam R-6 Per Inch R-12 R-24 R-48
Urea Foam R-5.25 Per Inch R-10.5 R-21 R-42
Urea-Formaldehyde Panels R-5.5 Per Inch R-11 R-22 R-44
High-Density XPS R-5.2 Per Inch R-10.4 R-20.8 R-41.6
Low-Density XPS R-4.15 Per Inch R-8.3 R-16.6 R-33.2
Polystyrene Board R-5 Per Inch R-10 R-20 R-40
Phenolic Spray Foam R-5.9 Per Inch R-11.8 R-23.6 R-47.2
Polyisocyanurate Spray Foam R-6.3 Per Inch R-12.6 R-25.2 R-50.4
High-Density EPS R-4.2 Per Inch R-8.4 R-16.8 R-33.6
Low-Density EPS R-3.85 Per Inch R-7.7 R-15.4 R-30.8
Phenolic Rigid Panel R-4.5 Per Inch R-9 R-18 R-38
Urea-Formaldehyde Foam R-4.3 Per Inch R-8.6 R-17.2 R-34.4
Icynene Loose-Fill R-4 Per Inch R-8 R-16 R-32
Home Foam R-3.9 Per Inch R-7.8 R-15.6 R-31.2
Cotton Batts R-3.7 Per Inch R-7.4 R-14.8 R-29.6
High-Density Fiberglass Batts R-4.3 Per Inch R-8.6 R-17.2 R-34.4
Icynene Spray R-3.6 Per Inch R-7.2 R-14.4 R-28.8
Open-Cell Polyurethane Spray Foam R-3.6 Per Inch R-7.2 R-14.4 R-28.8
Fiberglass Batts R-3.7 Per Inch R-7.4 R-14.8 R-29.6
Rice Hulls R-3 Per Inch R-6 R-12 R-24
Cardboard R-3.5 Per Inch R-7 R-14 R-28
Wool Batts R-3.4 Per Inch R-6.8 R-13.6 R-27.2
Loose-Fill Cellulose R-3.4 Per Inch R-6.8 R-13.6 R-27.2
Wet-Spray Cellulose R-3.4 Per Inch R-6.8 R-13.6 R-27.2
Polyethylene Foam R-3 Per Inch R-6 R-12 R-24
Loose-Fill Perlite R-2.7 Per Inch R-5.4 R-10.8 R-21.6
Papercrete R-2.9 Per Inch R-5.8 R-11.6 R-23.2
Loose-Fill Wool R-3.1 Per Inch R-6.2 R-12.4 R-24.8
Loose-Fill Fibergrass R-3.1 Per Inch R-6.2 R-12.4 R-24.8
Wood Panels (Sheathing) R-2.5 Per Inch R-5 R-10 R-20
Rigid Panel Fiberglass R-2.5 Per Inch R-5 R-10 R-20
Loose-Fill Vermiculite R-2.25 Per Inch R-4.5 R-9 R-18
Vermiculite R-2.13 Per Inch R-4.26 R-8.52 R-17.04
Cementitious Foam R-3 Per Inch R-6 R-12 R-24
Thinsulate Clothing Insulation R-2.35 Per Inch R-4.7 R-9.4 R-18.8
Straw Bale R-1.45 Per Inch R-2.9 R-5.8 R-11.6
Softwood R-1.41 Per Inch R-2.82 R-5.64 R-11.28
Loose-Fill Wood (Wood Chips) R-1 Per Inch R-2 R-4 R-8
Cellular Concrete R-1 Per Inch R-2 R-4 R-8
Drywall R-0.9 Per Inch R-1.8 R-3.6 R-7.2
Hardwood R-0.71 Per Inch R-1.42 R-2.84 R-5.68
Sheep Wool Batts R-3.7 Per Inch R-7.4 R-14.8 R-29.6
Glass R-0.14 Per Inch R-0.28 R-0.56 R-1.12
Brick R-0.2 Per Inch R-0.4 R-0.8 R-1.6
Poured Concrete R-0.08 Per Inch R-0.16 R-0.32 R-0.64
Soft Low-e Double Glazed Insulated Glass R-5.11 Per Inch R-10.22 R-20.44 R-40.88
Hard Low-e Double Glazed Insulated Glass R-3.8 Per Inch R-7.6 R-15.2 R-30.4
Double Glazed Insulated Glass R-2 Per Inch R-4 R-8 R-16
Triple Glazed Insulated Glass R-3.8 Per Inch R-7.6 R-15.2 R-30.4
Uninsulated Glass Pane R-0.91 Per Inch R-1.82 R-3.64 R-7.28

This R-value thickness table is pretty easy to use. You just check which material you want to use, read off the R-value, and compare the R-value of your material with other materials.

Here is a chart that illustrates graphically the differences between R-values for different insulation materials:

Insulation R-Value per inch Chart

Let’s address some of the questions we usually get when advising about insulation materials and their R-values:

Is A Higher R-Value Better For Insulation?

This goes without saying; higher R-values are better for insulation. The relationship between R-value and insulation is positive and linear.

Example: An R-10 insulation is twice as effective as R-5 insulation.

The higher the R-value insulation you use, the less you will spend on heating (in the winter) and cooling (in the summer).

What Is The Best R-Value For Insulation?

Same logic here; the higher the R-value, the better the insulation. The best R-value for insulation is as high as possible. Obviously, you will have to find a compromise between the R-value, the thickness of walls, ceilings, floors, roof, how much can you spend on insulation, and so on.

We can talk a bit about benchmarks about what is a good r value for insulation:

  • Exterior walls should have an R-value ranging from R-13 to R-23. A good R-value for exterior walls is R-23.
  • Attics can have R-30, R-38, or R-49. The best R-value for attics is R-49, or even higher. Is R30 insulation good for the attic? Well, it is about average; R-49 is better for the attic.
  • Ceilings can also have R-30, R-38, or R-49. If you can get a ceiling R-value of R-49, that is a good R-value.

As you can see, it makes sense to have high (R-40 or more) insulation values for places over your head (attics, ceilings). That’s where the hot air usually deprives your house of heat in the winter (increasing the cost of heating), and that is where the sun is shining in the summer, increasing the cost of air conditioning.

What Insulation Has The Highest R-Value?

In three words: Vacuum insulated panels (VIPs). These panels have, according to Wikipedia, ‘about five times the thermal resistance (R-value) per unit thickness’.

As you can see from the insulation R-value chart above, vacuum insulated panels have a typical R-value of R-25 per inch of thickness. Some VIPs can have R-value as high as R-45 or even R-50 per inch. This is an insulation material with the highest R-value altogether.

What Insulation Is Best For Exterior Walls?

A good exterior wall R-value is R-23. To achieve that, you can use any of these exterior wall insulation materials:

  • Fiberglass.
  • Foam boards.
  • Cellulose-based insulation.
  • Batt insulation.
  • Closed-cell or open-cell spray foam. Closed-cell spray foam is better for exterior walls because it is water-resistant, has a higher R-value per inch of thickness than open-cell type, but is also costlier.
closed cell and open cell spray foam r value per inch
Applying closed-cell spray foam on interior walls. Typical R-value is R-6 per inch.

What Is The Highest R-Value For A 2×4 Wall?

A 2×4 wall can hold either R-13 or R-15 fiberglass batts. So, if you were to use batt insulation, the highest R-value for a 2×4 wall is R-15.

This means that you are using a 4-inch batt with an average R-value of R-3.75 per inch of thickness.

Some people also ask if you can put R19 in 2×4 walls. Sadly, batts don’t have sufficient R-value per inch to accommodate for R-19 2×4 walls.

What Is The Highest R-Value For A 2×6 Wall?

A 2×6 wall can hold either R-13, R-15, R-19, or R-21 fiberglass batts. So, if you were to use batt insulation, the highest R-value for a 2×6 wall is R-21.

This means that you are using a 6-inch batt with an average R-value of R-3.5 per inch of thickness.


As stated before, if you have some questions regarding the insulation R-value chart, you can use the comments below and we will try to find an answer for you.

17 thoughts on “Insulation R-Value Chart: R-Values Per Inch (For 51 Materials)”

  1. Nice tables. Trying to compare cost to performance to total heat lose. So looking at all costs as a purchase point.
    Thanks for the introductory information.

    Reply
    • Hi Robert, thank you. Yes, it would be amazing if we could add the cost per R-value or per inch in the charts. The thing is that R-values per inch of insulation are fixed; prices of the insulation are volatile and depend on a number of factors. Hope you will find the most dollar-efficient insulation.

      Reply
  2. I would love to see more info on glass R-Values for windows and panes. What you have listed is a good start but glass is a whole different animal. Some examples I am having a hard time finding for:

    3/4″ Dual Paned glass, 1/4″ glass, 1/4″ air OR argon (with/out low-e coating)
    1″ Dual Paned: 1/4″ glass, 1/2″ air OR argon (with/out low-e coating)
    1.25″ Dual Paned, 1/2″ glass, 1/4″ air OR argon (with/out low-e coating)
    1.5″ Dual Paned, 1/2″ glass, 1/2″ air or argon (with/out low-e coating)

    This list could go on as the glass and the air/argon spacing gets thicker and thicker. What about all these scenarios in Triple paned glass?

    Glass gets heavier and heavier and much more pricey the thicker the panels become. Your models above showcase 2″, 4″ and 8″ – however, I can’t imagine 2″ glass panels, that would be some seriously heavy panes – and probably no one makes a 4″ or 8″.

    All my questions regarding glass come from research trying to find the best yet most affordable solution for glass panes for a wine room I am building in my house. Everyone states that dual paned insulated is best – yes, I get that, but what I can’t find is more specific info on 3/4″ dual paned vs 1.5″ dual paned or air vs argon spacing, etc etc etc. Whats the performance gain between these different thicknesses or densities vs the cost – is the extra gain worth the costs and is there a point where the gain is nominal but the cost is double?

    Thank you.

    Reply
    • Hi Russel, thank you for the suggestion. We will look into glass R-values and make a list in due time to help everybody looking for these elusive R-values out. In general, the extra insulation almost always pays off because you are calculating the savings for the next 20+ years. So, if double the price of glass can reduce the heating or cooling load by just a few percent, you are saving quite a lot in 20+ years.

      Reply
  3. Consider this scenario for the best solution to insulate my upper floor:
    I had a large tree shading my roof. It has been removed(cut down).
    This resulted in my upper floor getting warmer in the summer.
    I do have good insulation in the ceiling joists.
    What would be a better solution to regain a cooler summer in my top floor?
    Insulate my roof in between the roof rafters (closest to the underside of the roof itself) or add insulation to the existing insulation in the ceiling of the upper floor?
    Thanks for your input.

    Reply
    • Hi Gary, adding insulation between the roof rafters would be a better choice here. You will see that the upper floor, as well as the attic are cooler. Having a hot attic is a problem in itself and this solves it. Hope this helps.

      Reply
  4. Dear Sir/Madam,
    Beautiful tables. I love it .
    There is an insulation called STEICO, wood chips, extremely good quality insulation.
    Some sources say it has the R-value of 3.7, other say the U-value is 018 = R-5.5
    I know you can sort it out… 🙂
    THANK YOU KINDLY FOR YOUR TIME.

    Ladislav

    Reply
    • Hi Ladislav, yes, Steico is quite eco-friendly and has a relatively high insulation R-value. Here is the Steico specification sheet (including the R-values per inch). As you can see, there are about 20 different Steico insulation products such as STEICOtherm, STEICOfloor, STEICOroof, and so on. Most of Steico insulation products’ R-values per inch range between 2.9 and up to 4.0. The STEICOunderfloor has a lower 2.0 per inch R-value. Hope this helps.

      Reply
    • Hi Eric, here is a great resource on that from EnergyStar. Namely, Texas lies in Zone 2 (South Texas), Zone 3 (Central Texas), and Zone 4 (North Texas). For Zones 2 and 3, the recommended total attic R insulation value ranges from R30 to R60. In Zone 4, you should go for R38 to R60. Hope this helps.

      Reply
  5. Hi there,
    I work for the Southern Alberta Institute of Technology, and we are creating a Deep Energy Retrofit curriculum at the moment. I would love to use one of your graphs in our course. I was just curious if that would be ok, and when this article was created?

    Reply
    • Hi Dean, not sure about double foil faced foam. Usually, these foams are in 4-5 R value per inch range. 1/4 inch thickness should thus have about 1 R value (theoretically).

      Reply

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