R13 Insulation: All Your Questions Answered

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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. 

You may 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 briefly explain 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 R13 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.

R13 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. However, manufacturers craft the batt with some wiggle room for compression without compromising the R-value.

It’s essential to follow the manufacturer’s directions for compression wherever it’s necessary for a particular space. Compressing the insulation may cause it to lose 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 cutting the insulation to size easy. Depending on the R-value and manufacturer, the foam sheets can be anywhere from ½-inch to six inches thick. 

Most R13 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. 

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 R13 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.

R13 insulation is common in warmer climates, like Florida and Texas, because it offers additional protection and thermal resistance.

As you move into colder areas, like the Midwest and East Coast, R13 insulation won’t be enough.

However, insulation rated at R-13 is enough, depending on where you use it.


While you can use R13 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 significant source of heat loss in a home.

R13 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

R13 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, R13 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 R13 insulation for 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, R13 insulation is a solid choice for interior ceilings that separate floors.

For example, adding R13 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. They could get by just fine with R13 insulation.

However, people in moderate and cold climates might consider insulation with a higher R-value to keep their homes warmer and see actual energy savings.

Of course, if you have non-insulated areas, like a garage, that you want to insulate, adding R13 insulation is an improvement. Plus, it is a barrier to noise, pests, and, in many cases, moisture.

Other benefits of using R13 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.

R13 insulation is commonly seen as easy to install. Still, 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 on the floor or a crawlspace, wires, and ductwork will likely be in your path, so be aware and cautious.

R13 vs R15 Insulation

You have a tough decision if you’re trying to decide between R-13 and R-15 insulation.

The two R-values are relatively similar, though R-15 offers slightly better temperature regulation. Choose insulation with a higher R-value if you notice significant heat loss and noise issues.

Another consideration is installation because some R-15 insulation is typically more challenging. It comes in various lengths, but you usually have more R13 insulation options available.

There is also a difference in pricing. The pricing should be similar since the two R-values are so similar, but that is not always the case.

That wasn’t the case when looking at pricing through major retailers like Home Depot, Lowe’s, and Menard’s.

Unless you get a good deal on the R-15, you can expect to pay more for a higher R-value.

Some might argue that the R-15 is more efficient and will lead to energy savings.

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 Insulation

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 more consideration. 

The more significant difference between R-19 and R13 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 include those specifications. 

Many major retailers 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 Insulation

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 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, you typically won’t use R-21 insulation unless you have a new-build home.

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 Insulation

The comparison between R-13 and R-30 might be the most significant 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 mild 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 considering 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.

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