R-13 Insulation: All Your Questions Answered

You’ve seen the signs for a while. Rising energy bills, drafts by the crawlspace, and even cold floors signal a need for insulation. Replacing the insulation in your home can be a bit overwhelming. 

Maybe you have a vague idea about what R-values mean, but how do you know whether you need R-13 or R-30? 

In this article, we’ll give you a brief explanation of just what R-13 insulation is and how it compares to the other R-value insulation. Then, you can make the right decision for your home. 

How Thick is R13 Insulation? 

There are many R-13 insulation options to choose from, including fiberglass and rigid foam sheets. Though they all share an R-value, these products come in different thicknesses. 

For a quick primer on the difference between foam and batt insulation, click the link to my article explaining the differences.

R-13 fiberglass batt insulation is typically 3½ inches thick. However, some manufacturers offer slightly thicker batt, up to 3⅝ inches thick. Fiberglass batt is more flexible with room to compress to fit into tight spots. 

Most manufacturers cut the batt to fit standard frame sizes for uniformity in the process. However, manufacturers craft the batt with some wiggle room for compression without compromising the R-value.

It’s important to follow the manufacturer’s directions for compression wherever it’s necessary for a particular space. Compressing the insulation may cause it to lose its effectiveness, lowering the R-value.

Do not mistake rigid foam insulation for spray foam insulation. Rigid foam insulation comes in dense, rigid four-foot by eight-foot sheets, making it easy to cut the insulation to size. The foam sheets can be anywhere from ½-inch to six inches thick, depending on the R-value and manufacturer. 

Most R-13 rigid foam sheets are around two inches to 2½ inches thick. Unlike batt insulation, you don’t have to worry about compressing foam insulation type because it’s so dense. 

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According to the US Department of Energy, insulation thickness matters. Any changes can affect the R-value of the insulation.

For example, compressing the insulation too much can decrease the effectiveness and reduce the R-value. On the other hand, doubling the insulation, like putting two sheets of rigid foam together, can double the R-value and overall effectiveness.

What Is R-13 Insulation Used For?

Think of R-13 insulation as a giant blanket for your home. It fits perfectly into most walls, floors, and ceilings to manage temperature and moisture.

R-13 insulation is common in warmer climates, like Florida and Texas, because it offers a layer of protection and thermal resistance. As you move into colder areas, like the Midwest and East Coast, R-13 insulation won’t be enough on its own.

Depending on where you use it, insulation rated at R-13 could be enough, however.


While you can use R-13 insulation for attics, it’s typically not used alone because it doesn’t do as much to keep heat inside. Since heat rises, attics can be a major source of heat loss in a home. 

That said, R-13 insulation can fit nicely in attic spaces, but it’s best used to enhance existing or higher R-value insulation. It’s also a good option for enhancing existing insulation.

Exterior Walls

R-13 insulation works well for exterior walls because it’s made to fit those spaces, and it’s easy to install in exterior walls because you can wiggle it into place for a snug fit. Since it’s critical to have airtight insulation in exterior walls, R-13 insulation is a solid DIY choice. 

Unfortunately, R-13 insulation might not be enough for exterior walls in colder climates. Homeowners should select a higher R-value or double the R-13 insulation to get proper protection.


Ceilings run into similar situations as attics with heat rising and potentially escaping. It can be a good option for enhancing existing insulation.

Additionally, R-13 insulation is a solid choice for interior ceilings that separate floors. For example, adding R-13 insulation to the first-floor ceiling of a two-story home can do wonders. Since floors don’t always have insulation, you can keep more heat on the first floor and add some soundproofing to your garage

How Good Is R-13 Insulation?

Not all insulation is created equal, or there wouldn’t be a range of R-values to consider. How good R-13 insulation is depends heavily on where you live and how you plan to use it. 

People who live in warmer climates don’t usually have to worry about losing heat from their attics could get by just fine with R-13 insulation. However, people who live in moderate and cold climates might want to consider insulation with a higher R-value to keep their homes warmer and see real energy savings

Of course, if you have non-insulated areas, like garage, that you want to insulate, adding R-13 insulation is an improvement. Plus, it serves as a barrier to noise, pests, and in many cases, moisture.

Other benefits of using R-13 insulation include:

  • It’s easy to install without special equipment or protective gear.
  • The price is appealing for most people.
  • You don’t have to do a lot of prep work before installation.

R-13 insulation is commonly seen as easy to install, but it’s important to note that installing it in existing walls involves working around existing fixtures, like electrical boxes. You might want to hire a professional to handle the installation if you don’t have the necessary skills to work around that wiring. Even if you install it in the floor or a crawlspace, there will likely be wires and ductwork in your path, so be aware and cautious. 

R13 vs R15

If you’re trying to decide between R-13 and R-15 insulation, you have a tough decision to make. The two R-values are relatively similar, though R-15 offers slightly better temperature regulation. You might want to choose insulation with a higher R-value if you notice significant issues with heat loss and noise. 

Another consideration is installation because some R-15 insulation is typically more challenging. It does come in a range of lengths, but you usually have more R-13 options available.

There is also a difference in pricing. Since the two R-values are so similar, the pricing should be similar, but that is not always the case. Looking at pricing through major retailers, like Home Depot, Lowe’s, and Menard’s, that wasn’t the case. Unless you get a good deal on the R-15, you can expect to pay more for a higher R-value.

Some people might argue that the R-15 is more efficient and will lead to energy savings down the line. While that might be true to a degree, the difference may not be enough to justify the extra eight to ten dollars or more per roll for R-15 insulation.

R13 vs R19

If R-15 offers better thermal protection than R-13, you’d expect R-19 to be even better at keeping heat inside. You would be correct, however, comparing R-13 with R-19 takes a bit more consideration. 

The more important difference between R-19 and R-13 insulation is that they fit in different-sized spaces. More specifically, if you have a home with two-by-four studs, you should choose R-13 over the R-19 insulation. That’s because the R-19 insulation fits two-by-six spacing, so it’s often reserved for new builds that fit those specifications. 

Many major retailers seemed to price R-13 and R-19 insulation similarly. However, the R-19 was typically a little more expensive because of the higher R-value and increased efficiency.

You can find out more about R-19 insulation in my article here.

R13 vs R21

Comparing R-13 and R-21 insulation is similar to the R-19 comparison. Like R-19, R-21 insulation was designed to fit two-by-six stud spaces. However, it’s thinner and denser than the R-19 insulation. 

R-21 insulation might be an option for lining crawl spaces that are notorious for heat loss. However, it might require a spray foam or similar type of insulation to avoid cutting batt or board to fit it between the studs.

Again, unless you have a new-build home, you typically won’t use R-21 insulation. However, if you have the option, R-21 is superior to R-19. It’s slightly more expensive, but the upgrade can lead to long-term savings, with the R-21 being more energy-efficient.

R13 vs R30

The comparison between R-13 and R-30 might be the greatest leap on this list. While most professionals only recommend R-13 for warm climates, R-30 insulation is suitable in various scenarios, even for colder areas.

R-30 insulation is suitable for attics in warm to moderate climates, floors in moderate to cold climates, and as a buffer to existing insulation in most areas. It’s much thicker than R-13 in every form. For example, R-30 fiberglass batting is typically between eight and ten inches thick. Similarly, the R-30 rigid foam board ranges from 7½ inches to about 8⅓ inches.

Some versions of R-30 insulation offer water and fire resistance, but you will want to double-check with the manufacturer before selecting one for those purposes.

When you look at pricing, it’s best to view R-30 insulation as an investment. R-30 insulation can cost up to three times as much per square foot as the R-13 types.

However, when you look at the cost per square foot per R-value, it’s a less noticeable difference. R-30 insulation costs around $0.03 per square foot per R-value compared to $0.02 for R-13.

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Tim Wells

Tim Wells, the founder of Garage Transformed, has been featured in dozens of home renovation publications, including BobVila.com, Home Stratosphere, House Digest, Livingetc, and SFGate. Since 2018, he has helped over two million people transform their everyday garages into something they can be proud of. He lives in Central Florida with his wife and bulldog.